GCC for New Contributors

https://gcc-newbies-guide.readthedocs.io/en/latest/
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### Install GCC Prerequisites

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/getting-started.rst.txt

Installs all necessary development tools and libraries required for building GCC. This should be done once.

```bash
sudo apt install perl gawk binutils gcc-multilib \
python3 python3-pip gzip make tar zstd autoconf automake \
gettext gperf dejagnu autogen guile-3.0 expect tcl flex texinfo \
git diffutils patch git-email
```

--------------------------------

### Example Source Code

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/inside-cc1.html

This is an example of source code before lexing.

```c
return (b - c) * d;

```

--------------------------------

### Compile a simple C program

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/debugging.rst.txt

This is a basic C program used as an example for compilation.

```c
#include <stdio.h>

int main() {
    printf("Hello world\n");
    return 0;
}

```

--------------------------------

### Run Multiple Test Files and ABIs

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/working-with-the-testsuite.rst.txt

Execute tests from different .exp files and for multiple ABIs simultaneously. This example runs tests for both 32-bit and 64-bit ABIs.

```bash
make check-gcc \
    RUNTESTFLAGS="--target_board=unix\{-m32,-m64\} dg.exp='pr10474.c pr15698*.c' tree-ssa.exp=20030530-2.c"
```

--------------------------------

### C Code Example for Optimization Analysis

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/how-did-my-code-get-optimized.rst.txt

This C code serves as an example to demonstrate GCC optimization. It includes a recursive-like structure through function calls and a loop, which are targets for compiler optimizations.

```c
static int test (int a, int b, int c, int d)
{
  if (a)
    return (b - c) * d;
  else
    return (c - b) * d;
}

static int simple_loop (int n, int a, int b, int c, int d)
{
  int result;
  int i;
  for (i = 0; i < n)
    result += test (a, b, c, d);
  return result;
}

int fn_with_constants (void)
{
  return simple_loop (20, 1, 7, 4, 3);
}
```

--------------------------------

### Configure and Build GCC

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/getting-started.rst.txt

Configures the GCC build with a specified installation prefix and then initiates a parallel bootstrap build. Adjust '-j16' based on your system's core count.

```bash
mkdir build && cd build
../sources/configure --prefix "/path/to/gcc-control/install"
make -j16 bootstrap
```

--------------------------------

### Linker Command Line Example

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/binaries-and-processes.rst.txt

This command shows the full linker invocation by GCC, including input files, libraries, and various linker options. It is generated after the assembler has created object files.

```sh
/usr/libexec/gcc/x86_64-redhat-linux/10/collect2 \
     -plugin /usr/libexec/gcc/x86_64-redhat-linux/10/liblto_plugin.so \
       -plugin-opt=/usr/libexec/gcc/x86_64-redhat-linux/10/lto-wrapper \
       -plugin-opt=-fresolution=/tmp/cchv3sYK.res \
       -plugin-opt=-pass-through=-lgcc \
       -plugin-opt=-pass-through=-lgcc_s \
       -plugin-opt=-pass-through=-lc \
       -plugin-opt=-pass-through=-lgcc \
       -plugin-opt=-pass-through=-lgcc_s \
     --build-id \
     --no-add-needed \
     --eh-frame-hdr \
     --hash-style=gnu \
     -m elf_x86_64 \
     -dynamic-linker \
     /lib64/ld-linux-x86-64.so.2 \
     -o hello \
     /usr/lib/gcc/x86_64-redhat-linux/10/../../../../lib64/crt1.o \
     /usr/lib/gcc/x86_64-redhat-linux/10/../../../../lib64/crti.o \
     /usr/lib/gcc/x86_64-redhat-linux/10/crtbegin.o \
     -L/usr/lib/gcc/x86_64-redhat-linux/10 \
     -L/usr/lib/gcc/x86_64-redhat-linux/10/../../../../lib64 \
     -L/lib/../lib64 \
     -L/usr/lib/../lib64 \
     -L/usr/lib/gcc/x86_64-redhat-linux/10/../../.. \
     /tmp/ccXNu6jN.o \
     -lgcc \
     --push-state \
       --as-needed \
       -lgcc_s \
     --pop-state \
     -lc \
     -lgcc \
     --push-state \
       --as-needed \
       -lgcc_s \
     --pop-state \
     /usr/lib/gcc/x86_64-redhat-linux/10/crtend.o \
     /usr/lib/gcc/x86_64-redhat-linux/10/../../../../lib64/crtn.o
```

--------------------------------

### GIMPLE-SSA Form Example

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/inside-cc1.html

This snippet shows the GIMPLE-SSA form of a simple C function after optimization passes. It illustrates basic blocks, conditional jumps, variable versioning, and return statements.

```c
;; Function test (test, funcdef_no=0, decl_uid=1933, cgraph_uid=1, symbol_order=0)

test (int a, int b, int c, int d)
{
  int _1;
  int _2;
  int _3;
  int _8;
  int _9;

  <bb 2> [local count: 1073741824]:
  if (a_4(D) != 0)
    goto <bb 3>; [50.00%]
  else
    goto <bb 4>; [50.00%]

  <bb 3> [local count: 536870913]:
  _1 = b_6(D) - c_5(D);
  _9 = _1 * d_7(D);
  goto <bb 5>; [100.00%]

  <bb 4> [local count: 536870913]:
  _2 = c_5(D) - b_6(D);
  _8 = _2 * d_7(D);

  <bb 5> [local count: 1073741824]:
  # _3 = PHI <_9(3), _8(4)>
  return _3;

}

```

--------------------------------

### Macro definition for compiler options

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/debugging.html

Example of autogenerated preprocessor macro definitions for compiler options, showing how they map to internal variables.

```c
#ifdef GENERATOR_FILE
extern int optimize;
#else
  int x_optimize;
#define optimize global_options.x_optimize
#endif

```

```c
#ifdef GENERATOR_FILE
extern int flag_forward_propagate;
#else
  int x_flag_forward_propagate;
#define flag_forward_propagate global_options.x_flag_forward_propagate
#endif

```

--------------------------------

### GCC options.h macro definition

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/debugging.rst.txt

Example of how autogenerated preprocessor macros are defined in GCC's options.h.

```c++
#ifdef GENERATOR_FILE
extern int optimize;
#else
  int x_optimize;
#define optimize global_options.x_optimize
#endif

```

--------------------------------

### GDB output for non-existent symbols

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/debugging.rst.txt

Example of GDB output when attempting to print variables that are actually macros.

```console
(gdb) print optimize
No symbol "optimize" in current context.
(gdb) print flag_forward_propagate
No symbol "flag_forward_propagate" in current context.

```

--------------------------------

### Verbose Assembler Output with Comments

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/looking-at-the-generated-asm.rst.txt

This is an example of verbose assembler output generated with `-fverbose-asm`. It includes compiler version, options, and comments linking assembler instructions to C code.

```asm
	.file	"hello.c"
# GNU C17 (GCC) version 10.3.1 20210422 (Red Hat 10.3.1-1) (x86_64-redhat-linux)
#	compiled by GNU C version 10.3.1 20210422 (Red Hat 10.3.1-1), GMP version 6.2.0, MPFR version 4.1.0-p9, MPC version 1.1.0, isl version none
# GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
# options passed:  hello.c -mtune=generic -march=x86-64 -fverbose-asm
# options enabled:  -faggressive-loop-optimizations -fallocation-dce
# -fasynchronous-unwind-tables -fauto-inc-dec -fdelete-null-pointer-checks
# -fdwarf2-cfi-asm -fearly-inlining -feliminate-unused-debug-symbols
# -feliminate-unused-debug-types -ffp-int-builtin-inexact -ffunction-cse
# -fgcse-lm -fgnu-unique -fident -finline-atomics -fipa-stack-alignment
# -fira-hoist-pressure -fira-share-save-slots -fira-share-spill-slots
# -fivopts -fkeep-static-consts -fleading-underscore -flifetime-dse
# -fmath-errno -fmerge-debug-strings -fpeephole -fplt
# -fprefetch-loop-arrays -freg-struct-return
# -fsched-critical-path-heuristic -fsched-dep-count-heuristic
# -fsched-group-heuristic -fsched-interblock -fsched-last-insn-heuristic
# -fsched-rank-heuristic -fsched-spec -fsched-spec-insn-heuristic
# -fsched-stalled-insns-dep -fschedule-fusion -fsemantic-interposition
# -fshow-column -fshrink-wrap-separate -fsigned-zeros
# -fsplit-ivs-in-unroller -fssa-backprop -fstdarg-opt
# -fstrict-volatile-bitfields -fsync-libcalls -ftrapping-math -ftree-cselim
# -ftree-forwprop -ftree-loop-if-convert -ftree-loop-im -ftree-loop-ivcanon
# -ftree-loop-optimize -ftree-parallelize-loops= -ftree-phiprop
# -ftree-reassoc -ftree-scev-cprop -funit-at-a-time -funwind-tables
# -fverbose-asm -fzero-initialized-in-bss -m128bit-long-double -m64 -m80387
# -malign-stringops -mavx256-split-unaligned-load
# -mavx256-split-unaligned-store -mfancy-math-387 -mfp-ret-in-387 -mfxsr
# -mglibc -mieee-fp -mlong-double-80 -mmmx -mno-sse4 -mpush-args -mred-zone
# -msse -msse2 -mstv -mtls-direct-seg-refs -mvzeroupper
	.text
	.section	.rodata
.LC0:
	.string	"hello world"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushq	%rbp	#
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16

```

--------------------------------

### GCC Test Case with Show Caret and Multiline Output

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/how-to-improve-the-location-of-a-diagnostic.rst.txt

Example of a GCC test case using `-fdiagnostics-show-caret` to capture range information. It demonstrates how to use `dg-begin-multiline-output` and `dg-end-multiline-output` for testing multiline diagnostic output.

```c
/* { dg-options "-fdiagnostics-show-caret" } */
void test (void)
{
  enum { c1 = "not int", /* { dg-error "14: enumerator value for .c1. is not an integer constant" } */
  /* { dg-begin-multiline-output "" } 
enum { c1 = "not int",
              ^~~~~~~~~ 
  { dg-end-multiline-output "" } */

        c_end };
}
```

--------------------------------

### PHI Node Example in SSA

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/inside-cc1.rst.txt

Shows a PHI node construct in SSA form, which assigns a value to a temporary based on the control flow path taken.

```c
    # _3 = PHI <_9(3), _8(4)>
```

--------------------------------

### GCC RTL 'final' dump example

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/inside-cc1.rst.txt

This is a dump of the RTL in its 'final' form, suitable for assembler output. It shows the structure of instructions and control flow after optimization passes.

```lisp
;; Function test (test, funcdef_no=0, decl_uid=1933, cgraph_uid=1, symbol_order=0)



test

Dataflow summary:
;;  fully invalidated by EH 	 0 [ax] 1 [dx] 2 [cx] 4 [si] 5 [di] 8 [st] 9 [st(1)] 10 [st(2)] 11 [st(3)] 12 [st(4)] 13 [st(5)] 14 [st(6)] 15 [st(7)] 17 [flags] 18 [fpsr] 20 [xmm0] 21 [xmm1] 22 [xmm2] 23 [xmm3] 24 [xmm4] 25 [xmm5] 26 [xmm6] 27 [xmm7] 28 [mm0] 29 [mm1] 30 [mm2] 31 [mm3] 32 [mm4] 33 [mm5] 34 [mm6] 35 [mm7] 36 [r8] 37 [r9] 38 [r10] 39 [r11] 44 [xmm8] 45 [xmm9] 46 [xmm10] 47 [xmm11] 48 [xmm12] 49 [xmm13] 50 [xmm14] 51 [xmm15] 52 [xmm16] 53 [xmm17] 54 [xmm18] 55 [xmm19] 56 [xmm20] 57 [xmm21] 58 [xmm22] 59 [xmm23] 60 [xmm24] 61 [xmm25] 62 [xmm26] 63 [xmm27] 64 [xmm28] 65 [xmm29] 66 [xmm30] 67 [xmm31] 68 [k0] 69 [k1] 70 [k2] 71 [k3] 72 [k4] 73 [k5] 74 [k6] 75 [k7]
;;  hardware regs used 	 7 [sp]
;;  regular block artificial uses 	 7 [sp]
;;  eh block artificial uses 	 7 [sp] 16 [argp]
;;  entry block defs 	 0 [ax] 1 [dx] 2 [cx] 4 [si] 5 [di] 7 [sp] 20 [xmm0] 21 [xmm1] 22 [xmm2] 23 [xmm3] 24 [xmm4] 25 [xmm5] 26 [xmm6] 27 [xmm7] 36 [r8] 37 [r9]
;;  exit block uses 	 0 [ax] 7 [sp]
;;  regs ever live 	 0 [ax] 1 [dx] 2 [cx] 4 [si] 5 [di] 17 [flags]
;;  ref usage 	r0={4d,5u} r1={2d,3u} r2={1d,1u} r4={2d,3u} r5={1d,1u} r7={1d,4u} r17={5d,1u} r20={1d} r21={1d} r22={1d} r23={1d} r24={1d} r25={1d} r26={1d} r27={1d} r36={1d} r37={1d} 
;;    total ref usage 44{26d,18u,0e} in 11{11 regular + 0 call} insns.
(note 1 0 7 NOTE_INSN_DELETED)
(note 7 1 48 2 [bb 2] NOTE_INSN_BASIC_BLOCK)
(note 48 7 2 2 NOTE_INSN_PROLOGUE_END)
(note 2 48 6 2 NOTE_INSN_DELETED)
(note 6 2 5 2 NOTE_INSN_FUNCTION_BEG)
(insn:TI 5 6 9 2 (set (reg/v:SI 0 ax [orig:88 d ] [88])
          (reg:SI 2 cx [97])) "test.c":2:1 67 {*movsi_internal}
       (expr_list:REG_DEAD (reg:SI 2 cx [97])
          (nil)))
(insn 9 5 10 2 (set (reg:CCZ 17 flags)
          (compare:CCZ (reg:SI 5 di [94])
              (const_int 0 [0]))) "test.c":3:6 7 {*cmpsi_ccno_1}
       (expr_list:REG_DEAD (reg:SI 5 di [94])
          (nil)))
(jump_insn 10 9 11 2 (set (pc)
          (if_then_else (eq (reg:CCZ 17 flags)
                  (const_int 0 [0]))
              (label_ref 16)
              (pc))) "test.c":3:6 736 {*jcc}
       (expr_list:REG_DEAD (reg:CCZ 17 flags)
          (int_list:REG_BR_PROB 536870916 (nil))))
   -> 16)
(note 11 10 12 3 [bb 3] NOTE_INSN_BASIC_BLOCK)
(insn:TI 12 11 13 3 (parallel [
              (set (reg:SI 4 si [89])
                  (minus:SI (reg/v:SI 4 si [orig:86 b ] [86])
                      (reg/v:SI 1 dx [orig:87 c ] [87])))
              (clobber (reg:CC 17 flags))
          ]) "test.c":4:15 254 {*subsi_1}
       (expr_list:REG_DEAD (reg/v:SI 1 dx [orig:87 c ] [87])
          (expr_list:REG_UNUSED (reg:CC 17 flags)
              (nil))))
(insn:TI 13 12 52 3 (parallel [
              (set (reg:SI 0 ax [orig:84 <retval> ] [84])
                  (mult:SI (reg/v:SI 0 ax [orig:88 d ] [88])
                      (reg:SI 4 si [89])))
              (clobber (reg:CC 17 flags))
          ]) "test.c":4:20 378 {*mulsi3_1}
       (expr_list:REG_DEAD (reg:SI 4 si [89])
          (expr_list:REG_UNUSED (reg:CC 17 flags)
              (nil))))
(insn 52 13 45 3 (use (reg/i:SI 0 ax)) -1
       (nil))
(jump_insn:TI 45 52 46 3 (simple_return) "test.c":4:20 767 {simple_return_internal}
       (nil)
   -> simple_return)
(barrier 46 45 16)
(code_label 16 46 17 4 2 (nil) [1 uses])
(note 17 16 18 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
(insn:TI 18 17 19 4 (parallel [
              (set (reg:SI 1 dx [90])
                  (minus:SI (reg/v:SI 1 dx [orig:87 c ] [87])
                      (reg/v:SI 4 si [orig:86 b ] [86])))
              (clobber (reg:CC 17 flags))
          ]) "test.c":6:15 254 {*subsi_1}
       (expr_list:REG_DEAD (reg/v:SI 4 si [orig:86 b ] [86])
          (expr_list:REG_UNUSED (reg:CC 17 flags)
              (nil))))
(insn:TI 19 18 26 4 (parallel [
              (set (reg:SI 0 ax [orig:84 <retval> ] [84])
                  (mult:SI (reg/v:SI 0 ax [orig:88 d ] [88])
                      (reg:SI 1 dx [90])))
              (clobber (reg:CC 17 flags))
          ]) "test.c":6:20 378 {*mulsi3_1}

```

--------------------------------

### Run executable

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/binaries-and-processes.rst.txt

Executes the compiled program, which prints 'hello world' to standard output.

```sh
$ ./hello
hello world
```

--------------------------------

### Compile a C program

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/debugging.html

Standard C code for a 'Hello, world!' program.

```c
#include <stdio.h>

int main (int argc, const char *argv[])
{
   printf ("Hello world\n");
   return 0;
}

```

--------------------------------

### C Program: hello.c

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/binaries-and-processes.html

A basic C program that prints 'hello world' to the console.

```c
#include <stdio.h>
int main ()
{
  printf ("hello world\n");
  return 0;
}

```

--------------------------------

### Get Token Location in C++

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/how-to-improve-the-location-of-a-diagnostic.rst.txt

Retrieves the location of the current token being parsed. This is often an implicit source for diagnostics and may be improved.

```c++
value_loc = c_parser_peek_token (parser)->location;
```

--------------------------------

### SSA Temporaries Assignment Example

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/inside-cc1.rst.txt

Illustrates how assignments to a single temporary in an earlier IR form are split into separate temporaries in SSA form.

```c
    D.1938 = d * _1;
```

```c
    D.1938 = d * _2;
```

```c
    _9 = d_7(D) * _1;
```

```c
    _8 = d_7(D) * _2;
```

--------------------------------

### Lexing: C Source to Tokens

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/inside-cc1.rst.txt

Illustrates the transformation of C source code characters into a stream of tokens during the lexing phase. This is the initial step before parsing.

```none
return (b - c) * d;
```

```none
CPP_KEYWORD(RID_RETURN)
CPP_OPEN_PAREN
CPP_NAME("b")
CPP_MINUS
CPP_NAME("c")
CPP_CLOSE_PAREN
CPP_MULT
CPP_NAME("d")
CPP_SEMICOLON
```

--------------------------------

### GCC RTL Dump

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/inside-cc1.html

This is an example of the Register Transfer Language (RTL) generated by GCC after the 'expand' optimization pass. It shows the low-level operations on registers and memory.

```gcc-rtl
;; Function test (test, funcdef_no=0, decl_uid=1933, cgraph_uid=1, symbol_order=0)


;; Generating RTL for gimple basic block 2

;; Generating RTL for gimple basic block 3

;; Generating RTL for gimple basic block 4

;; Generating RTL for gimple basic block 5


try_optimize_cfg iteration 1

Merging block 3 into block 2...
Merged blocks 2 and 3.
Merged 2 and 3 without moving.
Redirecting jump 14 from 6 to 7.
Merging block 6 into block 5...
Merged blocks 5 and 6.
Merged 5 and 6 without moving.
Removing jump 22.


try_optimize_cfg iteration 2



;;
;; Full RTL generated for this function:
;;
(note 1 0 7 NOTE_INSN_DELETED)
(note 7 1 2 2 [bb 2] NOTE_INSN_BASIC_BLOCK)
(insn 2 7 3 2 (set (reg/v:SI 85 [ a ])
        (reg:SI 5 di [ a ]))) "test.c":2:1 -1
     (nil))
(insn 3 2 4 2 (set (reg/v:SI 86 [ b ])
        (reg:SI 4 si [ b ]))) "test.c":2:1 -1
     (nil))
(insn 4 3 5 2 (set (reg/v:SI 87 [ c ])
        (reg:SI 1 dx [ c ]))) "test.c":2:1 -1
     (nil))
(insn 5 4 6 2 (set (reg/v:SI 88 [ d ])
        (reg:SI 2 cx [ d ]))) "test.c":2:1 -1
     (nil))
(note 6 5 9 2 NOTE_INSN_FUNCTION_BEG)
(insn 9 6 10 2 (set (reg:CCZ 17 flags)
        (compare:CCZ (reg/v:SI 85 [ a ])
            (const_int 0 [0]))) "test.c":3:6 -1
     (nil))
(jump_insn 10 9 11 2 (set (pc)
        (if_then_else (eq (reg:CCZ 17 flags)
                (const_int 0 [0]))
            (label_ref 16)
            (pc))) "test.c":3:6 -1
     (int_list:REG_BR_PROB 536870916 (nil))
 -> 16)
(note 11 10 12 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
(insn 12 11 13 4 (parallel [
            (set (reg:SI 89)
                (minus:SI (reg/v:SI 86 [ b ])
                    (reg/v:SI 87 [ c ])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":4:15 -1
     (nil))
(insn 13 12 14 4 (parallel [
            (set (reg:SI 84 [ <retval> ])
                (mult:SI (reg:SI 89)
                    (reg/v:SI 88 [ d ])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":4:20 -1
     (nil))
(jump_insn 14 13 15 4 (set (pc)
        (label_ref:DI 24))) "test.c":4:20 737 {jump}
     (nil)
 -> 24)
(barrier 15 14 16)
(code_label 16 15 17 5 2 (nil) [1 uses])
(note 17 16 18 5 [bb 5] NOTE_INSN_BASIC_BLOCK)
(insn 18 17 19 5 (parallel [
            (set (reg:SI 90)
                (minus:SI (reg/v:SI 87 [ c ])
                    (reg/v:SI 86 [ b ])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":6:15 -1
     (nil))
(insn 19 18 24 5 (parallel [
            (set (reg:SI 84 [ <retval> ])
                (mult:SI (reg:SI 90)
                    (reg/v:SI 88 [ d ])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":6:20 -1
     (nil))
(code_label 24 19 27 7 1 (nil) [1 uses])
(note 27 24 25 7 [bb 7] NOTE_INSN_BASIC_BLOCK)
(insn 25 27 26 7 (set (reg/i:SI 0 ax)
        (reg:SI 84 [ <retval> ])) "test.c":7:1 -1
     (nil))
(insn 26 25 0 7 (use (reg/i:SI 0 ax)) "test.c":7:1 -1
     (nil))
```

--------------------------------

### List files in directory

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/binaries-and-processes.rst.txt

Lists files in the current directory, showing the generated executable and the source file.

```sh
$ ls
hello  hello.c
```

--------------------------------

### Get Token Location in C Parser

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/how-to-improve-the-location-of-a-diagnostic.html

Retrieves the location of the first token within an expression. This is often less informative than the expression's full range.

```c
value_loc = c_parser_peek_token (parser)->location;

```

--------------------------------

### Compile and run a C program

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/debugging.html

Command-line instructions to compile and execute a C program using GCC.

```bash
$ gcc hello.c
$ ./a.out
Hello world

```

--------------------------------

### Clone GCC Sources and Download Prerequisites

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/getting-started.rst.txt

Clones the GCC source code repository and downloads its specific prerequisites using a provided script. Ensure you are in the desired parent directory.

```bash
mkdir -p gcc-control
cd gcc-control
git clone git://gcc.gnu.org/git/gcc.git sources
cd gcc-control
./sources/contrib/download_prerequisites
```

--------------------------------

### GIMPLE SSA Form Example

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/inside-cc1.rst.txt

This GIMPLE code represents a basic block in Static Single Assignment (SSA) form, showing variable assignments and control flow.

```c
goto <bb 3>; [50.00%]
    else
      goto <bb 4>; [50.00%]
  
    <bb 3> [local count: 536870913]:
    _1 = b_6(D) - c_5(D);
    _9 = _1 * d_7(D);
    goto <bb 5>; [100.00%]
  
    <bb 4> [local count: 536870913]:
    _2 = c_5(D) - b_6(D);
    _8 = _2 * d_7(D);
  
    <bb 5> [local count: 1073741824]:
    # _3 = PHI <_9(3), _8(4)>
    return _3;
  
  }
```

--------------------------------

### Build GCC with Bootstrap

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/getting-started.html

Use this command to build GCC for a bootstrap build. Omit the 'bootstrap' target for a regular build.

```bash
make -j16 bootstrap
```

--------------------------------

### Run GCC Tests with Multiple Wildcards and ABIs

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/working-with-the-testsuite.html

Execute tests from different .exp files using wildcards and specify multiple target ABIs (e.g., 32-bit and 64-bit) within RUNTESTFLAGS.

```bash
make check-gcc \
  RUNTESTFLAGS="--target_board=unix\{-m32,-m64\} dg.exp='pr10474.c pr15698*.c' tree-ssa.exp=20030530-2.c"

```

--------------------------------

### Compile C code to executable

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/binaries-and-processes.html

Compiles a C source file into an executable file named 'hello'.

```bash
$ gcc hello.c -o hello
```

--------------------------------

### Use EXPR_LOC_OR_LOC Macro

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/how-to-improve-the-location-of-a-diagnostic.rst.txt

A utility macro to get the location of an expression, providing a fallback if direct location information is unavailable. Useful for emitting multiple locations or fix-it hints.

```c++
EXPR_LOC_OR_LOC (expr, fallback_location)
```

--------------------------------

### Regstrap Patch and Run Test Suite

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/_sources/readying-a-patch.rst.txt

This bash script performs the regstrap process for a patched GCC version, including cleaning the build directory, configuring, bootstrapping, and running the full test suite. It's followed by a comparison with the control build.

```bash
cd /path/to/gcc-patched
# Cleanup your build folder
rm -r build && mkdir build
cd build
# configure WITHOUT disabling bootstrap.
../sources/configure --prefix=/path/to/gcc-patched/install
# Run the full testsuite.
make -j16 bootstrap && make -k -j16 check
# Compare the result of your regstrap with control's
# Be sure you understand the output. If you have a doubt,
# better ask the mail list.
../sources/contrib/compare_tests /path/to/gcc-control/build .
```

--------------------------------

### C Code Example for Tree Dump

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/inside-cc1.html

This C code snippet is used to generate a 'tree' dump, showing the intermediate representation after parsing. It demonstrates a simple conditional return statement.

```c
;; Function test (null)
;; enabled by -tree-original


{
  if (a != 0)
    {
      return (b - c) * d;
    }
  else
    {
      return (c - b) * d;
    }
}


```

--------------------------------

### Compile C Program with GCC

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/binaries-and-processes.html

Command to compile a C program using GCC.

```bash
gcc hello.c -o hello
```

--------------------------------

### Use EXPR_LOC_OR_LOC Macro

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/how-to-improve-the-location-of-a-diagnostic.html

A utility macro to get the location of an expression, falling back to a provided location if the expression itself doesn't have one. Useful for emitting multiple locations or fix-it hints.

```c
EXPR_LOC_OR_LOC (expr, fallback_location)

```

--------------------------------

### Assembler Invocation by GCC

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/binaries-and-processes.html

Demonstrates how the GCC driver invokes the assembler ('as') with specific options for processing assembly files into object files.

```text
COLLECT_GCC_OPTIONS='-o' 'hello' '-v' '-mtune=generic' '-march=x86-64'
 as -v --64 -o /tmp/ccXNu6jN.o /tmp/cckqYOSJ.s
GNU assembler version 2.35 (x86_64-redhat-linux) using BFD version version 2.35-18.fc33

```

```text
as -v --64 -o /tmp/ccXNu6jN.o /tmp/cckqYOSJ.s

```

--------------------------------

### Parallel Build with Make

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/getting-started.html

Builds GCC using parallel processing to speed up the compilation time. Adjust -jN based on your system's cores.

```bash
# I have 16 cores on my box, so I use -j16 to parallelize as much as possible
make -j16
```

--------------------------------

### Compiling C to Assembler with Optimization

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/inside-cc1.html

Command to compile a C file to assembly, enabling optimization and verbose assembly output. Use this to inspect the generated assembly code.

```bash
$ gcc -S test.c -O2 -fverbose-asm

```

--------------------------------

### GCC Test Case with Diagnostics Show Caret

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/how-to-improve-the-location-of-a-diagnostic.html

Example of a GCC test case using `-fdiagnostics-show-caret` to capture range information. It includes expected error output and multiline output markers for testing caret placement.

```c
/* { dg-options "-fdiagnostics-show-caret" } */
void test (void)
{
  enum { c1 = "not int", /* { dg-error "14: enumerator value for .c1. is not an integer constant" } */
  /* { dg-begin-multiline-output "" }
   enum { c1 = "not int",
               ^~~~~~~~~ 
     { dg-end-multiline-output "" } */

      c_end };
}

```

--------------------------------

### Configure GCC Build

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/getting-started.html

Configures the GCC build environment. Use --disable-bootstrap for faster rebuilds during development.

```bash
mkdir build && cd build
# here you would add --disable-bootstrap for your 'draft' directory
../sources/configure --prefix "/path/to/gcc-control/install"
```

--------------------------------

### GCC RTL Final Dump Example

Source: https://gcc-newbies-guide.readthedocs.io/en/latest/inside-cc1.html

This dump file represents the final RTL form of a function after the 'final' optimization pass. It is used as input for assembler generation. Note that this is a representation of intermediate compiler code, not C source.

```gcc-rtl
;; Function test (test, funcdef_no=0, decl_uid=1933, cgraph_uid=1, symbol_order=0)



test

Dataflow summary:
;;  fully invalidated by EH    0 [ax] 1 [dx] 2 [cx] 4 [si] 5 [di] 8 [st] 9 [st(1)] 10 [st(2)] 11 [st(3)] 12 [st(4)] 13 [st(5)] 14 [st(6)] 15 [st(7)] 17 [flags] 18 [fpsr] 20 [xmm0] 21 [xmm1] 22 [xmm2] 23 [xmm3] 24 [xmm4] 25 [xmm5] 26 [xmm6] 27 [xmm7] 28 [mm0] 29 [mm1] 30 [mm2] 31 [mm3] 32 [mm4] 33 [mm5] 34 [mm6] 35 [mm7] 36 [r8] 37 [r9] 38 [r10] 39 [r11] 44 [xmm8] 45 [xmm9] 46 [xmm10] 47 [xmm11] 48 [xmm12] 49 [xmm13] 50 [xmm14] 51 [xmm15] 52 [xmm16] 53 [xmm17] 54 [xmm18] 55 [xmm19] 56 [xmm20] 57 [xmm21] 58 [xmm22] 59 [xmm23] 60 [xmm24] 61 [xmm25] 62 [xmm26] 63 [xmm27] 64 [xmm28] 65 [xmm29] 66 [xmm30] 67 [xmm31] 68 [k0] 69 [k1] 70 [k2] 71 [k3] 72 [k4] 73 [k5] 74 [k6] 75 [k7]
;;  hardware regs used         7 [sp]
;;  regular block artificial uses      7 [sp]
;;  eh block artificial uses   7 [sp] 16 [argp]
;;  entry block defs   0 [ax] 1 [dx] 2 [cx] 4 [si] 5 [di] 7 [sp] 20 [xmm0] 21 [xmm1] 22 [xmm2] 23 [xmm3] 24 [xmm4] 25 [xmm5] 26 [xmm6] 27 [xmm7] 36 [r8] 37 [r9]
;;  exit block uses    0 [ax] 7 [sp]
;;  regs ever live     0 [ax] 1 [dx] 2 [cx] 4 [si] 5 [di] 17 [flags]
;;  ref usage         r0={4d,5u} r1={2d,3u} r2={1d,1u} r4={2d,3u} r5={1d,1u} r7={1d,4u} r17={5d,1u} r20={1d} r21={1d} r22={1d} r23={1d} r24={1d} r25={1d} r26={1d} r27={1d} r36={1d} r37={1d}
;;    total ref usage 44{26d,18u,0e} in 11{11 regular + 0 call} insns.
(note 1 0 7 NOTE_INSN_DELETED)
(note 7 1 48 2 [bb 2] NOTE_INSN_BASIC_BLOCK)
(note 48 7 2 2 NOTE_INSN_PROLOGUE_END)
(note 2 48 6 2 NOTE_INSN_DELETED)
(note 6 2 5 2 NOTE_INSN_FUNCTION_BEG)
(insn:TI 5 6 9 2 (set (reg/v:SI 0 ax [orig:88 d ] [88])
        (reg:SI 2 cx [97])) "test.c":2:1 67 {*movsi_internal}
     (expr_list:REG_DEAD (reg:SI 2 cx [97])
        (nil)))
(insn 9 5 10 2 (set (reg:CCZ 17 flags)
        (compare:CCZ (reg:SI 5 di [94])
            (const_int 0 [0]))) "test.c":3:6 7 {*cmpsi_ccno_1}
     (expr_list:REG_DEAD (reg:SI 5 di [94])
        (nil)))
(jump_insn 10 9 11 2 (set (pc)
        (if_then_else (eq (reg:CCZ 17 flags)
                (const_int 0 [0]))
            (label_ref 16)
            (pc)))"test.c":3:6 736 {*jcc}
     (expr_list:REG_DEAD (reg:CCZ 17 flags)
        (int_list:REG_BR_PROB 536870916 (nil)))
 -> 16)
(note 11 10 12 3 [bb 3] NOTE_INSN_BASIC_BLOCK)
(insn:TI 12 11 13 3 (parallel [
            (set (reg:SI 4 si [89])
                (minus:SI (reg/v:SI 4 si [orig:86 b ] [86])
                    (reg/v:SI 1 dx [orig:87 c ] [87])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":4:15 254 {*subsi_1}
     (expr_list:REG_DEAD (reg/v:SI 1 dx [orig:87 c ] [87])
        (expr_list:REG_UNUSED (reg:CC 17 flags)
            (nil))))
(insn:TI 13 12 52 3 (parallel [
            (set (reg:SI 0 ax [orig:84 <retval> ] [84])
                (mult:SI (reg/v:SI 0 ax [orig:88 d ] [88])
                    (reg:SI 4 si [89])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":4:20 378 {*mulsi3_1}
     (expr_list:REG_DEAD (reg:SI 4 si [89])
        (expr_list:REG_UNUSED (reg:CC 17 flags)
            (nil))))
(insn 52 13 45 3 (use (reg/i:SI 0 ax)) -1
     (nil))
(jump_insn:TI 45 52 46 3 (simple_return) "test.c":4:20 767 {simple_return_internal}
     (nil)
 -> simple_return)
(barrier 46 45 16)
(code_label 16 46 17 4 2 (nil) [1 uses])
(note 17 16 18 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
(insn:TI 18 17 19 4 (parallel [
            (set (reg:SI 1 dx [90])
                (minus:SI (reg/v:SI 1 dx [orig:87 c ] [87])
                    (reg/v:SI 4 si [orig:86 b ] [86])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":6:15 254 {*subsi_1}
     (expr_list:REG_DEAD (reg/v:SI 4 si [orig:86 b ] [86])
        (expr_list:REG_UNUSED (reg:CC 17 flags)
            (nil))))
(insn:TI 19 18 26 4 (parallel [
            (set (reg:SI 0 ax [orig:84 <retval> ] [84])
                (mult:SI (reg/v:SI 0 ax [orig:88 d ] [88])
                    (reg:SI 1 dx [90])))
            (clobber (reg:CC 17 flags))
        ]) "test.c":6:20 378 {*mulsi3_1}
     (expr_list:REG_DEAD (reg:SI 1 dx [90])
        (expr_list:REG_UNUSED (reg:CC 17 flags)
            (nil))))
(insn 26 19 55 4 (use (reg/i:SI 0 ax)) "test.c":7:1 -1
     (nil))
(note 55 26 50 4 NOTE_INSN_EPILOGUE_BEG)
(jump_insn:TI 50 55 51 4 (simple_return) "test.c":7:1 767 {simple_return_internal}
     (nil)
 -> simple_return)
(barrier 51 50 47)
(note 47 51 0 NOTE_INSN_DELETED)

```
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