Merge commit '11a0cceab9' into subtree-update_cg_gcc_2023-10-09

compiler/rustc_codegen_gcc/doc/add-attribute.md

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+# Add support for a new function attribute
+
+To add support for a new function attribute in libgccjit, you need to do the following steps:
+
+ 1. Copy the corresponding function from `c-family/c-attribs.cc` into `jit/dummy-frontend.cc`. For example if you add the `target` attribute, the function name will be `handle_target_attribute`.
+ 2. Copy the corresponding entry from the `c_common_attribute_table` variable in the `c-family/c-attribs.cc` file into the `jit_attribute_table` variable in `jit/dummy-frontend.cc`.
+ 3. Add a new variant in the `gcc_jit_fn_attribute` enum in the `jit/libgccjit.h` file.
+ 4. Add a test to ensure the attribute is correctly applied in `gcc/testsuite/jit.dg/`. Take a look at `gcc/testsuite/jit.dg/test-nonnull.c` if you want an example.
+ 5. Run the example like this (in your `gcc-build` folder): `make check-jit RUNTESTFLAGS="-v -v -v jit.exp=jit.dg/test-nonnull.c"`
+
+Once done, you need to update the [gccjit.rs] crate to add the new enum variant in the corresponding enum (`FnAttribute`).
+
+Finally, you need to update this repository by calling the relevant API you added in [gccjit.rs].
+
+To test it, build `gcc`, run `cargo update -p gccjit` and then you can test the generated output for a given Rust crate.
+
+[gccjit.rs]: https://github.com/antoyo/gccjit.rs

compiler/rustc_codegen_gcc/doc/gimple.md

@@ -0,0 +1,111 @@
+# 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.

compiler/rustc_codegen_gcc/doc/sending-gcc-patch.md

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+This guide explains what to do to send a GCC patch for review.
+
+All the commands are supposed to be run in the folder where you cloned GCC.
+
+```bash
+./contrib/gcc-changelog/git_check_commit.py
+```
+
+You can provide a specific commit hash:
+
+```bash
+./contrib/gcc-changelog/git_check_commit.py abdef78989
+```
+
+a range:
+
+```bash
+./contrib/gcc-changelog/git_check_commit.py HEAD~2
+```
+
+or even a comparison with a remote branch:
+
+```bash
+./contrib/gcc-changelog/git_check_commit.py upstream/master..HEAD
+```
+
+When there is no more errors, generate the git patch:
+
+```bash
+git format-patch -1 `git rev-parse --short HEAD`
+```
+
+Then you can run the remaining checks using:
+
+```bash
+contrib/check_GNU_style.sh 0001-your-patch.patch
+```
+
+When you have no more errors, you can send the `.patch` file to GCC by sending an
+email to `gcc-patches@gcc.gnu.org` and to the relevant GCC mailing lists
+depending on what your patch changes. You can find the list of the mailing lists
+[here](https://gcc.gnu.org/lists.html).
+
+You can find more information about "contributing to GCC" [here](https://gcc.gnu.org/contribute.html).