GCC, GNU compiler collection

GCC : GNU compilers collection Alberto Bustamante Reyes ( www.albertobustamante.com ) Author:

Brief introduction
Compiler system developed by GNU Project
Distributed by FSF under GPL License
Written in C / C++
Default compiler for Unix and Mac OS X
Also ported to Windows (MinGW)

Brief introduction
Originally developed for C language
Several front-ends added to support different languages:
C / C++ (gcc / g++)
Java (gcj)
Objective-C / Objective-C++ (gobjc / gobjc++ )
Fortran (gfortran)

Structure
Generic compiler:
Front end
Back end
GCC compiler:
Front end
Middle end
Back end

Structure
GCC Compiler (before 2005)
Source code AST RTL RTL Object code FRONT END BACK END

Structure
GCC Compiler (before 2005)
Source code AST RTL RTL Object code FRONT END BACK END SSA Tree project: OPTIMIZATIONS

Structure
GCC Compiler (after 2005)
Source code AST GENERIC GIMPLE RTL FRONT END

Structure
Source code AST GENERIC GIMPLE RTL FRONT END Language dependent Language independent

Structure
Source code AST GENERIC GIMPLE RTL FRONT END Language dependent Language independent MIDDLE END

Structure: GENERIC & GIMPLE
Why two kinds of trees?
GIMPLE is a simplified subset of GENERIC
GIMPLE GENERIC

GENERIC -> (Gimplifier) -> GIMPLE
GIMPLIFIER if (foo ( a + b, c)) c = b ++ / a end if return c t1 = a +b t2 = foo (t1, c) If (t2 != 0 ) <L1, L2> L1: t3 = b b = b + 1 c = t3 / a goto L3 L2: L3: return c

Developed by SSA Tree Project
SSA
Developed by IBM in 1980
Single Static Assignment
Example:
y := 1 y := 2 x := y y1 := 1 y2 := 2 x1 := y2

Structure: Middle end GIMPLE Tree SSA Optimizer RTL

Structure:Middle end
SSA Tree Optimization
Dead code elimination
y := 1 y := 2 x := y y1 := 1 y2 := 2 x1 := y2

Partial redundancy elimination
if (some_condition) { // some code y = x + 4; }else { // other code } z = x + 4; if (some_condition) { // some code y = x + 4; t = y; }else { // other code t = x + 4; } z = t;

Global value numbering
w := 3 x := 3 y := x + 4 z := w + 4 w := 3 x := w y := w + 4 z := y

Sparse conditional constant propagation

Sparse conditional constant propagation
Scalar replacement of aggregates

Structure: RTL
Output of the Middle End
Processor dependent
Looks like Lisp S-expressions:
(set:SI (reg:SI 140) (plus:SI (reg:SI 138) (reg:SI 139)))

Structure: summary Source code AST GENERIC GIMPLE Tree SSA Optimizer RTL Optimized RTL Object code FRONT END MIDDLE END BACK END

Advantages of using GCC
Reliable
Suppported by GNU & FSF
Active and noumerous developer team
One of the most popular compilers
Lots of test cases (users)
Several front ends
Free!!

More information available at…
GCC : http://gcc.gnu.org
GCC Wiki : http://gcc.gnu.org/wiki
SSA Tree Project: http://gcc.gnu.org/projects/tree-ssa/
GNU : http://www.gnu.org
Free Software Foundation : http://www.fsf.org
MinGW: http://www.mingw.org

The End Thanks for watching

GCC : GNU compilers collection Alberto Bustamante Reyes ( www.albertobustamante.com ) Author:

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GCC, GNU compiler collection

by albbus on Oct 01, 2011

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