112 lines
3.1 KiB
Markdown
112 lines
3.1 KiB
Markdown
# GIMPLE
|
|
|
|
You can see the full documentation about what GIMPLE is [here](https://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html). In this document we will explain how to generate it.
|
|
|
|
First, we'll copy the content from `gcc/gcc/testsuite/jit.dg/test-const-attribute.c` into a
|
|
file named `local.c` and remove the content we're not interested into:
|
|
|
|
```diff
|
|
- /* { dg-do compile { target x86_64-*-* } } */
|
|
...
|
|
- /* We don't want set_options() in harness.h to set -O3 to see that the const
|
|
- attribute affects the optimizations. */
|
|
- #define TEST_ESCHEWS_SET_OPTIONS
|
|
- static void set_options (gcc_jit_context *ctxt, const char *argv0)
|
|
- {
|
|
- // Set "-O3".
|
|
- gcc_jit_context_set_int_option(ctxt, GCC_JIT_INT_OPTION_OPTIMIZATION_LEVEL, 3);
|
|
- }
|
|
-
|
|
- #define TEST_COMPILING_TO_FILE
|
|
- #define OUTPUT_KIND GCC_JIT_OUTPUT_KIND_ASSEMBLER
|
|
- #define OUTPUT_FILENAME "output-of-test-const-attribute.c.s"
|
|
- #include "harness.h"
|
|
...
|
|
- /* { dg-final { jit-verify-output-file-was-created "" } } */
|
|
- /* Check that the loop was optimized away */
|
|
- /* { dg-final { jit-verify-assembler-output-not "jne" } } */
|
|
```
|
|
|
|
Then we'll add a `main` function which will call the `create_code` function but
|
|
also add the calls we need to generate the GIMPLE:
|
|
|
|
```C
|
|
int main() {
|
|
gcc_jit_context *ctxt = gcc_jit_context_acquire();
|
|
// To set `-O3`, update it depending on your needs.
|
|
gcc_jit_context_set_int_option(ctxt, GCC_JIT_INT_OPTION_OPTIMIZATION_LEVEL, 3);
|
|
// Very important option to generate the gimple format.
|
|
gcc_jit_context_set_bool_option(ctxt, GCC_JIT_BOOL_OPTION_DUMP_INITIAL_GIMPLE, 1);
|
|
create_code(ctxt, NULL);
|
|
|
|
gcc_jit_context_compile(ctxt);
|
|
// If you want to compile to assembly (or any other format) directly, you can
|
|
// use the following call instead:
|
|
// gcc_jit_context_compile_to_file(ctxt, GCC_JIT_OUTPUT_KIND_ASSEMBLER, "out.s");
|
|
|
|
return 0;
|
|
}
|
|
```
|
|
|
|
Then we can compile it by using:
|
|
|
|
```console
|
|
gcc local.c -I `pwd`/gcc/gcc/jit/ -L `pwd`/gcc-build/gcc -lgccjit -o out
|
|
```
|
|
|
|
And finally when you run it:
|
|
|
|
```console
|
|
LD_LIBRARY_PATH=`pwd`/gcc-build/gcc LIBRARY_PATH=`pwd`/gcc-build/gcc ./out
|
|
```
|
|
|
|
It should display:
|
|
|
|
```c
|
|
__attribute__((const))
|
|
int xxx ()
|
|
{
|
|
int D.3394;
|
|
int sum;
|
|
int x;
|
|
|
|
<D.3377>:
|
|
x = 45;
|
|
sum = 0;
|
|
goto loop_cond;
|
|
loop_cond:
|
|
x = x >> 1;
|
|
if (x != 0) goto after_loop; else goto loop_body;
|
|
loop_body:
|
|
_1 = foo (x);
|
|
_2 = _1 * 2;
|
|
x = x + _2;
|
|
goto loop_cond;
|
|
after_loop:
|
|
D.3394 = sum;
|
|
return D.3394;
|
|
}
|
|
```
|
|
|
|
An alternative way to generate the GIMPLE is to replace:
|
|
|
|
```c
|
|
gcc_jit_context_set_bool_option(ctxt, GCC_JIT_BOOL_OPTION_DUMP_INITIAL_GIMPLE, 1);
|
|
```
|
|
|
|
with:
|
|
|
|
```c
|
|
gcc_jit_context_add_command_line_option(ctxt, "-fdump-tree-gimple");
|
|
```
|
|
|
|
(although you can have both at the same time too). Then you can compile it like previously. Only one difference: before executing it, I recommend to run:
|
|
|
|
```console
|
|
rm -rf /tmp/libgccjit-*
|
|
```
|
|
|
|
to make it easier for you to know which folder to look into.
|
|
|
|
Once the execution is done, you should now have a file with path looking like `/tmp/libgccjit-9OFqkD/fake.c.006t.gimple` which contains the GIMPLE format.
|