CS 715: The Design and Implementation of Gnu Compiler Generation Framework
Uday Khedker
GCC Resource Center,
Department of Computer Science and Engineering, Indian Institute of Technology, Bombay
January 2011
CS 715 Gnu Compiler Collection: Outline 1/55
Outline
•
An Overview of Compilation
Introduction, compilation sequence, compilation models
•
GCC: The Great Compiler Challenge Difficulties in understanding GCC
•
Meeting the GCC Challenge: CS 715
The course plan
Part 1
Introduction to Compilation
CS 715 Gnu Compiler Collection: Introduction to Compilation 2/55
Binding
Time No.of
unbound objects
Nothing is known except the problem
CS 715 Gnu Compiler Collection: Introduction to Compilation 2/55
Binding
Time No.of
unbound objects
Conceptualisation
Overall strategy, algorithm, data structures etc.
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 2/55
Binding
Time No.of
unbound objects
Conceptualisation Coding
Functions, variables, their types etc.
CS 715 Gnu Compiler Collection: Introduction to Compilation 2/55
Binding
Time No.of
unbound objects
Conceptualisation Coding Compiling
Machine instructions, registers etc.
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 2/55
Binding
Time No.of
unbound objects
Conceptualisation Coding Compiling Linking
Addresses of functions, external data etc.
CS 715 Gnu Compiler Collection: Introduction to Compilation 2/55
Binding
Time No.of
unbound objects
Conceptualisation Coding Compiling Linking Loading
Actual addresses of code and data
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 2/55
Binding
Time No.of
unbound objects
Conceptualisation Coding Compiling Linking Loading Execution Values of variables
CS 715 Gnu Compiler Collection: Introduction to Compilation 3/55
Implementation Mechanisms
Source Program
Translator Target Program
Machine
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 3/55
Implementation Mechanisms
Source Program
Translator Target Program
Machine
Input Data
CS 715 Gnu Compiler Collection: Introduction to Compilation 3/55
Implementation Mechanisms
Source Program
Translator Target Program
Machine
Input Data
Source Program
Interpreter Machine
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 4/55
Implementation Mechanisms as “Bridges”
•
“Gap” between the “levels” of program specification and execution
Program Specification
Machine
CS 715 Gnu Compiler Collection: Introduction to Compilation 4/55
Implementation Mechanisms as “Bridges”
•
“Gap” between the “levels” of program specification and execution
Program Specification
Machine Translation
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 4/55
Implementation Mechanisms as “Bridges”
•
“Gap” between the “levels” of program specification and execution
Program Specification
Machine
Translation Interpretation
CS 715 Gnu Compiler Collection: Introduction to Compilation 4/55
Implementation Mechanisms as “Bridges”
•
“Gap” between the “levels” of program specification and execution
Program Specification
Machine
Translation Interpretation
State : Variables Operations: Expressions,
Control Flow
State : Memory, Registers Operations: Machine
Instructions
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 5/55
High and Low Level Abstractions
Input C statement a = b<10?b:c;
Spim Assembly Equivalent
lw $t0, 4($fp) ; t0 <- b # Is b smaller slti $t0, $t0, 10 ; t0 <- t0 < 10 # than 10?
not $t0, $t0 ; t0 <- !t0
bgtz $t0, L0: ; if t0>=0 goto L0 lw $t0, 4($fp) ; t0 <- b # YES
b L1: ; goto L1
L0: lw $t0, 8($fp) ;L0: t0 <- c # NO L1: sw 0($fp), $t0 ;L1: a <- t0
CS 715 Gnu Compiler Collection: Introduction to Compilation 5/55
High and Low Level Abstractions
Input C statement a = b<10?b:c;
Spim Assembly Equivalent
lw $t0, 4($fp) ; t0 <- b # Is b smaller slti $t0, $t0, 10 ; t0 <- t0 < 10 # than 10?
not $t0, $t0 ; t0 <- !t0
bgtz $t0, L0: ; if t0>=0 goto L0 lw $t0, 4($fp) ; t0 <- b # YES
b L1: ; goto L1
L0: lw $t0, 8($fp) ;L0: t0 <- c # NO L1: sw 0($fp), $t0 ;L1: a <- t0
Condition False Part True Part
Fall through Conditional jump
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 5/55
High and Low Level Abstractions
Input C statement a = b<10?b:c;
Spim Assembly Equivalent
lw $t0, 4($fp) ; t0 <- b # Is b smaller slti $t0, $t0, 10 ; t0 <- t0 < 10 # than 10?
not $t0, $t0 ; t0 <- !t0
bgtz $t0, L0: ; if t0>=0 goto L0 lw $t0, 4($fp) ; t0 <- b # YES
b L1: ; goto L1
L0: lw $t0, 8($fp) ;L0: t0 <- c # NO L1: sw 0($fp), $t0 ;L1: a <- t0
NOT Condition True Part False Part
CS 715 Gnu Compiler Collection: Introduction to Compilation 5/55
High and Low Level Abstractions
Input C statement a = b<10?b:c;
Spim Assembly Equivalent
lw $t0, 4($fp) ; t0 <- b # Is b smaller slti $t0, $t0, 10 ; t0 <- t0 < 10 # than 10?
not $t0, $t0 ; t0 <- !t0
bgtz $t0, L0: ; if t0>=0 goto L0 lw $t0, 4($fp) ; t0 <- b # YES
b L1: ; goto L1
L0: lw $t0, 8($fp) ;L0: t0 <- c # NO L1: sw 0($fp), $t0 ;L1: a <- t0
NOT Condition True Part False Part
Fall through Conditional jump
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 6/55
Implementation Mechanisms
•
Translation = Analysis + Synthesis
Interpretation = Analysis + Execution
CS 715 Gnu Compiler Collection: Introduction to Compilation 6/55
Implementation Mechanisms
•
Translation = Analysis + Synthesis Interpretation = Analysis + Execution
•
Translation Instructions Equivalent Instructions
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 6/55
Implementation Mechanisms
•
Translation = Analysis + Synthesis Interpretation = Analysis + Execution
•
Translation Instructions Equivalent Instructions
Interpretation Instructions Actions Implied
by Instructions
CS 715 Gnu Compiler Collection: Introduction to Compilation 7/55
Language Implementation Models
Analysis
Synthesis
Execution
Compilation
Interpretation
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 8/55
Language Processor Models
C,C
++
Java, C#
Front
End Optimizer
Back End
Virtual
Machine
CS 715 Gnu Compiler Collection: Introduction to Compilation 9/55
Typical Front Ends
Parser
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 9/55
Typical Front Ends
Parser Source
Program
Scanner
Tokens
CS 715 Gnu Compiler Collection: Introduction to Compilation 9/55
Typical Front Ends
Parser Source
Program
Scanner
Tokens
Semantic Analyzer AST
Parse Tree
AST or Linear IR Symbol Table+
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 9/55
Typical Front Ends
Parser Source
Program
Scanner
Tokens
Semantic Analyzer AST
Parse Tree
AST or Linear IR Symbol Table+
Error Handler Symtab
Handler
CS 715 Gnu Compiler Collection: Introduction to Compilation 10/55
Typical Back Ends
m/c Ind.
IR
m/c Ind.
Optimizer
−
Compile time evaluations
−
Eliminating redundant computations
m/c Ind.
IR
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 10/55
Typical Back Ends
m/c Ind.
IR
m/c Ind.
Optimizer
−
Compile time evaluations
−
Eliminating redundant computations
m/c Ind.
IR
Code Generator
Dep. m/c IR
−
Instruction Selection
−
Local Reg Allocation
−
Choice of Order of
Evaluation
CS 715 Gnu Compiler Collection: Introduction to Compilation 10/55
Typical Back Ends
m/c Ind.
IR
m/c Ind.
Optimizer
−
Compile time evaluations
−
Eliminating redundant computations
m/c Ind.
IR
Code Generator
Dep. m/c IR
−
Instruction Selection
−
Local Reg Allocation
−
Choice of Order of Evaluation
m/c Dep.
Optimizer
Assembly Code
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: Introduction to Compilation 10/55
Typical Back Ends
m/c Ind.
IR
m/c Ind.
Optimizer
−
Compile time evaluations
−
Eliminating redundant computations
m/c Ind.
IR
Code Generator
Dep. m/c IR
−
Instruction Selection
−
Local Reg Allocation
−
Choice of Order of Evaluation
Assembly Code Register
Allocator
Instruction Scheduler Peephole
Optimizer
Part 2
An Overview of Compilation Phases
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 11/55
The Structure of a Simple Compiler
Parser
Scanner Semantic Analyser
Symtab Handler Source Program
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 11/55
The Structure of a Simple Compiler
Parser
Scanner Semantic Analyser
Symtab Handler Source Program
Instruction Selector AST
Register Allocator
Assembly Emitter Insn
Assembly Program
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 11/55
The Structure of a Simple Compiler
Parser
Scanner Semantic Analyser
Symtab Handler Source Program
Instruction Selector AST
Register Allocator
Assembly Emitter Insn
Assembly Program
Front End Back End
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 12/55
Translation Sequence in Our Compiler: Parsing
a=b<10?b:c;
Input
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 12/55
Translation Sequence in Our Compiler: Parsing
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree Issues:
• Grammar rules, terminals, non-terminals
• Order of application of grammar rules eg. is it(a = b<10?) followed by(b:c)?
• Values of terminal symbols
eg. string “10” vs. integer number 10.
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 13/55
Translation Sequence in Our Compiler: Semantic Analysis
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 13/55
Translation Sequence in Our Compiler: Semantic Analysis
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
= name
(a,int) ?: (int)
<
(bool) name (b,int)
name (c,int) name
(b,int) num (10,int) Abstract Syntax Tree
(with attributes) Issues:
• Symbol tables
Have variables been declared? What are their types?
What is their scope?
• Type consistency of operators and operands The result of computing b<10?is bool and not int
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 14/55
Translation Sequence in Our Compiler: IR Generation
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
= name
(a,int) ?: (int)
<
(bool) name (b,int)
name (c,int) name
(b,int) num (10,int) Abstract Syntax Tree
(with attributes)
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 14/55
Translation Sequence in Our Compiler: IR Generation
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
= name
(a,int) ?: (int)
<
(bool) name (b,int)
name (c,int) name
(b,int) num (10,int) Abstract Syntax Tree
(with attributes)
= T0 <
b 10
IfGoto
Not L0:
T0
=
T1 b
Goto L1:
=
T1 c
L0:
= T1 a
L1:
Tree List
Issues:
• Convert to maximal trees which can be implemented without altering control flow Simplifies instruction selection and scheduling, register allocation etc.
• Linearise control flow by flattening nested control constructs
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 15/55
Translation Sequence in Our Compiler: Instruction Selection
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
= name
(a,int) ?: (int)
<
(bool) name (b,int)
name (c,int) name
(b,int) num (10,int) Abstract Syntax Tree
(with attributes)
= T0 <
b 10
IfGoto
Not L0:
T0
=
T1 b
Goto L1:
=
T1 c
L0:
= T1 a
L1:
Tree List
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 15/55
Translation Sequence in Our Compiler: Instruction Selection
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
= name
(a,int) ?: (int)
<
(bool) name (b,int)
name (c,int) name
(b,int) num (10,int) Abstract Syntax Tree
(with attributes)
= T0 <
b 10
IfGoto
Not L0:
T0
=
T1 b
Goto L1:
=
T1 c
L0:
= T1 a
L1:
Tree List
T0 ←b T0 ← T0 <10 T0 ←!T0 ifT0 > 0 goto L0:
T1 ←b goto L1:
L0:T1 ←c L1: a← T1
Instruction List Issues:
• Cover trees with as few machine instructions as possible
• Use temporaries and local registers
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 16/55
Translation Sequence in Our Compiler: Emitting Instructions
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
= name
(a,int) ?: (int)
<
(bool) name (b,int)
name (c,int) name
(b,int) num (10,int) Abstract Syntax Tree
(with attributes)
= T0 <
b 10
IfGoto
Not L0:
T0
=
T1 b
Goto L1:
=
T1 c
L0:
= T1 a
L1:
Tree List
T0 ←b T0 ← T0 <10 T0 ←!T0 ifT0 > 0 goto L0:
T1 ←b goto L1:
L0:T1 ←c L1: a← T1
Instruction List
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: An Overview of Compilation Phases 16/55
Translation Sequence in Our Compiler: Emitting Instructions
a=b<10?b:c;
Input
AsgnStmnt
Lhs = E ;
E ? E : E
E < E name
name name
name num
Parse Tree
= name
(a,int) ?: (int)
<
(bool) name (b,int)
name (c,int) name
(b,int) num (10,int) Abstract Syntax Tree
(with attributes)
= T0 <
b 10
IfGoto
Not L0:
T0
=
T1 b
Goto L1:
=
T1 c
L0:
= T1 a
L1:
Tree List
T0 ←b T0 ← T0 <10 T0 ←!T0 ifT0 > 0 goto L0:
T1 ←b goto L1:
L0:T1 ←c L1: a← T1
Instruction List
lw $t0, 4($fp) slti $t0, $t0, 10 not $t0, $t0 bgtz $t0, L0:
lw $t0, 4($fp) b L1:
L0: lw $t0, 8($fp) L1: sw 0($fp), $t0 Assembly Code Issues:
• Offsets of variables in the stack frame
• Actual register numbers and assembly mnemonics
• Code to construct and discard activation records
Part 3
Compilation Models, Instruction Selection, and
Retargetability
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model Input Source Program
Front End AST
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model Input Source Program
Front End AST Optimizer m/c indep. IR
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model Input Source Program
Front End AST Optimizer m/c indep. IR
Code Generator Target Program
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model Input Source Program
Front End AST Optimizer m/c indep. IR
Code Generator Target Program
Front End AST
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model Input Source Program
Front End AST Optimizer m/c indep. IR
Code Generator Target Program
Front End AST Expander register transfers
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model Input Source Program
Front End AST Optimizer m/c indep. IR
Code Generator Target Program
Front End AST Expander register transfers
Optimizer register transfers
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model Input Source Program
Front End AST Optimizer m/c indep. IR
Code Generator Target Program
Front End AST Expander register transfers
Optimizer register transfers
Recognizer Target Program
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 17/55
Compilation Models
Aho Ullman Model
Davidson Fraser Model
Front End AST Optimizer m/c indep. IR
Code Generator Target Program
Front End AST Expander register transfers
Optimizer register transfers
Recognizer Target Program Aho Ullman: Instruction selection
• over optimized IR using
• intelligent tree tiling based algorithms
Davidson Fraser: Instruction selection
• over AST using
• simple full tree matching based algorithms that generate
• naive code which is
◮ machine dependent, and is
◮ optimized subsequently
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 18/55
Retargetability in Aho Ullman Model
Front End AST Optimizer m/c indep. IR
Code Generator Target Program
Instruction selection
•
over optimized IR using
•
intelligent tree tiling based algorithms Key idea in retargetability:
•
Machine independent IR is expressed in the form of trees
•
Machine instructions are described in the form of trees
•
Trees in the IR are tiled using the instruction trees
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 19/55
Retargetability in Davidson Fraser Model
Front End AST Expander register transfers
Optimizer register transfers
Recognizer Target Program
Instruction selection
•
over AST using
•
simple full tree matching based algorithms that generate
•
naive code which is
◮ machine dependent, and is
◮ optimized subsequently
Key idea in retargetability:
•
Register transfers are machine specific but
•
their form is machine independent
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 20/55
Full Tree Matching (Davidson Fraser Model)
Instructions are viewed as independent non-composable rules
Machine Instructions Subject Tree (IR) Modified Trees
=
reg +
reg reg
=
reg
∗reg reg
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 20/55
Full Tree Matching (Davidson Fraser Model)
Instructions are viewed as independent non-composable rules
Machine Instructions Subject Tree (IR) Modified Trees
=
reg +
reg reg
=
reg
∗reg reg
=
a
+
a ∗
b c
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 20/55
Full Tree Matching (Davidson Fraser Model)
Instructions are viewed as independent non-composable rules
Machine Instructions Subject Tree (IR) Modified Trees
=
reg +
reg reg
=
reg
∗reg reg
=
a
+
a ∗
b c
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 20/55
Full Tree Matching (Davidson Fraser Model)
Instructions are viewed as independent non-composable rules
Machine Instructions Subject Tree (IR) Modified Trees
=
reg +
reg reg
=
reg
∗reg reg
=
a
+
a ∗
b c
=
t ∗
b c
=
a
+
a t
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 20/55
Full Tree Matching (Davidson Fraser Model)
Instructions are viewed as independent non-composable rules
Machine Instructions Subject Tree (IR) Modified Trees
=
reg +
reg reg
=
reg
∗reg reg
=
a
+
a ∗
b c
=
t ∗
b c
=
a
+
a t
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 20/55
Full Tree Matching (Davidson Fraser Model)
Instructions are viewed as independent non-composable rules
Machine Instructions Subject Tree (IR) Modified Trees
=
reg +
reg reg
=
reg
∗reg reg
=
a
+
a ∗
b c
=
t ∗
b c
=
a
+
a t
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
reg +
Reg Reg
∗
Reg Reg
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
+
a ∗
b c
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
+
a ∗
b c
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
+
Reg
∗Reg Reg
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
+
Reg
∗Reg Reg
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
+
Reg Reg
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
+
Reg Reg
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
Reg
Uday Khedker GRC, IIT Bombay
CS 715Gnu Compiler Collection: Compilation Models, Instruction Selection, and Retargetability 21/55
Tree Tiling (Aho Ullman Model) Instructions are viewed as composable rules
Machine Instructions Subject Tree (IR)
=
reg Reg
Reg reg
+
Reg Reg
Reg
∗
Reg Reg
Reg
=
a
Reg
Part 4
GCC ≡ The Great Compiler Challenge
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 22/55
The Gnu Tool Chain
gcc Source Program
Target Program
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 22/55
The Gnu Tool Chain
gcc Source Program
Target Program
cc1
cppUday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 22/55
The Gnu Tool Chain
gcc Source Program
Target Program
cc1 cpp
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 22/55
The Gnu Tool Chain
gcc Source Program
Target Program
cc1 cpp
as
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 22/55
The Gnu Tool Chain
gcc Source Program
Target Program
cc1 cpp
as
ld
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 22/55
The Gnu Tool Chain
gcc Source Program
Target Program
cc1 cpp
as
ld
glibc/newlib
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 22/55
The Gnu Tool Chain
gcc Source Program
Target Program
cc1 cpp
as
ld
glibc/newlib
GCC
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 23/55
Why is Understanding GCC Difficult?
•
Some of the obvious reasons:
◮ Comprehensiveness
GCC is a production quality framework in terms of completeness and practical usefulness
◮ Open development model
Could lead to heterogeneity. Design flaws may be difficult to correct
◮ Rapid versioning
GCC maintenance is a race against time. Disruptive corrections are difficult
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 24/55
Why is Understanding GCC Difficult?
•
Deeper technical reasons:
◮ GCC is not a compiler but acompiler generation framework Two distinct gaps that need to be bridged:
◮ Input-output of the generation framework
◮ Input-output of the generated compiler
◮ GCC generated compiler uses a derivative of the Davidson-Fraser model of compilation
◮ Early instruction selection
◮ Machine dependent intermediate representation
◮ Simplistic instruction selection and retargatibility mechanism
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86),
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC,
◮ Lesser-known target processors:
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K,
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC,
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC, ETRAX CRIS,
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC, ETRAX CRIS, D30V,
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC, ETRAX CRIS, D30V, DSP16xx,
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC, ETRAX CRIS, D30V, DSP16xx, FR-30,
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC, ETRAX CRIS, D30V, DSP16xx, FR-30, FR-V,
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC, ETRAX CRIS, D30V, DSP16xx, FR-30, FR-V, Intel i960,
◮ Additional processors independently supported:
CS 715 Gnu Compiler Collection: GCC≡The Great Compiler Challenge 25/55
Comprehensiveness of GCC: Wide Applicability
•
Input languages supported:
C, C++, Objective-C, Objective-C++, Java, Fortran, and Ada
•
Processors supported in standard releases:
◮ Common processors:
Alpha, ARM, Atmel AVR, Blackfin, HC12, H8/300, IA-32 (x86), x86-64, IA-64, Motorola 68000, MIPS, PA-RISC, PDP-11, PowerPC, R8C/M16C/M32C, SPU,
System/390/zSeries, SuperH, SPARC, VAX
◮ Lesser-known target processors:
A29K, ARC, ETRAX CRIS, D30V, DSP16xx, FR-30, FR-V, Intel i960, IP2000,
◮ Additional processors independently supported:
Uday Khedker GRC, IIT Bombay