Merging upstream version 1.75.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 120 insertions, 24 deletions

diff --git a/compiler/rustc_codegen_gcc/Readme.md b/compiler/rustc_codegen_gcc/Readme.md
index a93637d90..95fc6374c 100644
--- a/compiler/rustc_codegen_gcc/Readme.md
+++ b/compiler/rustc_codegen_gcc/Readme.md
@@ -1,6 +1,7 @@
 # WIP libgccjit codegen backend for rust
 
 [![Chat on IRC](https://img.shields.io/badge/irc.libera.chat-%23rustc__codegen__gcc-blue.svg)](https://web.libera.chat/#rustc_codegen_gcc)
+[![Chat on Matrix](https://img.shields.io/badge/matrix.org-%23rustc__codegen__gcc-blue.svg)](https://matrix.to/#/#rustc_codegen_gcc:matrix.org)
 
 This is a GCC codegen for rustc, which means it can be loaded by the existing rustc frontend, but benefits from GCC: more architectures are supported and GCC's optimizations are used.
 
@@ -14,9 +15,7 @@ A secondary goal is to check if using the gcc backend will provide any run-time
 ## Building
 
 **This requires a patched libgccjit in order to work.
-The patches in [this repository](https://github.com/antoyo/libgccjit-patches) need to be applied.
-(Those patches should work when applied on master, but in case it doesn't work, they are known to work when applied on 079c23cfe079f203d5df83fea8e92a60c7d7e878.)
-You can also use my [fork of gcc](https://github.com/antoyo/gcc) which already includes these patches.**
+You need to use my [fork of gcc](https://github.com/antoyo/gcc) which already includes these patches.**
 
 To build it (most of these instructions come from [here](https://gcc.gnu.org/onlinedocs/jit/internals/index.html), so don't hesitate to take a look there if you encounter an issue):
 
@@ -56,18 +55,11 @@ $ make check-jit RUNTESTFLAGS="-v -v -v jit.exp=jit.dg/test-asm.cc"
 $ dirname $(readlink -f `find . -name libgccjit.so`) > gcc_path
 ```
 
-You also need to set RUST_COMPILER_RT_ROOT:
-
-```bash
-$ git clone https://github.com/llvm/llvm-project llvm --depth 1 --single-branch
-$ export RUST_COMPILER_RT_ROOT="$PWD/llvm/compiler-rt"
-```
-
 Then you can run commands like this:
 
 ```bash
-$ ./prepare.sh # download and patch sysroot src and install hyperfine for benchmarking
-$ LIBRARY_PATH=$(cat gcc_path) LD_LIBRARY_PATH=$(cat gcc_path) ./build.sh --release
+$ ./y.sh prepare # download and patch sysroot src and install hyperfine for benchmarking
+$ LIBRARY_PATH=$(cat gcc_path) LD_LIBRARY_PATH=$(cat gcc_path) ./y.sh build --release
 ```
 
 To run the tests:
@@ -78,22 +70,37 @@ $ ./test.sh --release
 
 ## Usage
 
-`$cg_gccjit_dir` is the directory you cloned this repo into in the following instructions.
+`$CG_GCCJIT_DIR` is the directory you cloned this repo into in the following instructions:
+
+```bash
+export CG_GCCJIT_DIR=[the full path to rustc_codegen_gcc]
+```
 
 ### Cargo
 
 ```bash
-$ CHANNEL="release" $cg_gccjit_dir/cargo.sh run
+$ CHANNEL="release" $CG_GCCJIT_DIR/cargo.sh run
 ```
 
 If you compiled cg_gccjit in debug mode (aka you didn't pass `--release` to `./test.sh`) you should use `CHANNEL="debug"` instead or omit `CHANNEL="release"` completely.
 
+### LTO
+
+To use LTO, you need to set the variable `FAT_LTO=1` and `EMBED_LTO_BITCODE=1` in addition to setting `lto = "fat"` in the `Cargo.toml`.
+Don't set `FAT_LTO` when compiling the sysroot, though: only set `EMBED_LTO_BITCODE=1`.
+
+Failing to set `EMBED_LTO_BITCODE` will give you the following error:
+
+```
+error: failed to copy bitcode to object file: No such file or directory (os error 2)
+```
+
 ### Rustc
 
 > You should prefer using the Cargo method.
 
 ```bash
-$ rustc +$(cat $cg_gccjit_dir/rust-toolchain) -Cpanic=abort -Zcodegen-backend=$cg_gccjit_dir/target/release/librustc_codegen_gcc.so --sysroot $cg_gccjit_dir/build_sysroot/sysroot my_crate.rs
+$ LIBRARY_PATH=$(cat gcc_path) LD_LIBRARY_PATH=$(cat gcc_path) rustc +$(cat $CG_GCCJIT_DIR/rust-toolchain | grep 'channel' | cut -d '=' -f 2 | sed 's/"//g' | sed 's/ //g') -Cpanic=abort -Zcodegen-backend=$CG_GCCJIT_DIR/target/release/librustc_codegen_gcc.so --sysroot $CG_GCCJIT_DIR/build_sysroot/sysroot my_crate.rs
 ```
 
 ## Env vars
@@ -105,8 +112,18 @@ $ rustc +$(cat $cg_gccjit_dir/rust-toolchain) -Cpanic=abort -Zcodegen-backend=$c
     object files when their content should have been changed by a change to cg_gccjit.</dd>
     <dt>CG_GCCJIT_DISPLAY_CG_TIME</dt>
     <dd>Display the time it took to perform codegen for a crate</dd>
+    <dt>CG_RUSTFLAGS</dt>
+    <dd>Send additional flags to rustc. Can be used to build the sysroot without unwinding by setting `CG_RUSTFLAGS=-Cpanic=abort`.</dd>
+    <dt>CG_GCCJIT_DUMP_TO_FILE</dt>
+    <dd>Dump a C-like representation to /tmp/gccjit_dumps and enable debug info in order to debug this C-like representation.</dd>
 </dl>
 
+## Licensing
+
+While this crate is licensed under a dual Apache/MIT license, it links to `libgccjit` which is under the GPLv3+ and thus, the resulting toolchain (rustc + GCC codegen) will need to be released under the GPL license.
+
+However, programs compiled with `rustc_codegen_gcc` do not need to be released under a GPL license.
+
 ## Debugging
 
 Sometimes, libgccjit will crash and output an error like this:
@@ -182,6 +199,61 @@ set substitute-path /usr/src/debug/gcc /path/to/gcc-repo/gcc
 
 TODO(antoyo): but that's not what I remember I was doing.
 
+### `failed to build archive` error
+
+When you get this error:
+
+```
+error: failed to build archive: failed to open object file: No such file or directory (os error 2)
+```
+
+That can be caused by the fact that you try to compile with `lto = "fat"`, but you didn't compile the sysroot with LTO.
+(Not sure if that's the reason since I cannot reproduce anymore. Maybe it happened when forgetting setting `FAT_LTO`.)
+
+### ld: cannot find crtbegin.o
+
+When compiling an executable with libgccijt, if setting the `*LIBRARY_PATH` variables to the install directory, you will get the following errors:
+
+```
+ld: cannot find crtbegin.o: No such file or directory
+ld: cannot find -lgcc: No such file or directory
+ld: cannot find -lgcc: No such file or directory
+libgccjit.so: error: error invoking gcc driver
+```
+
+To fix this, set the variables to `gcc-build/build/gcc`.
+
+### How to debug GCC LTO
+
+Run do the command with `-v -save-temps` and then extract the `lto1` line from the output and run that under the debugger.
+
+### How to send arguments to the GCC linker
+
+```
+CG_RUSTFLAGS="-Clink-args=-save-temps -v" ../cargo.sh build
+```
+
+### How to see the personality functions in the asm dump
+
+```
+CG_RUSTFLAGS="-Clink-arg=-save-temps -v -Clink-arg=-dA" ../cargo.sh build
+```
+
+### How to see the LLVM IR for a sysroot crate
+
+```
+cargo build -v --target x86_64-unknown-linux-gnu -Zbuild-std
+# Take the command from the output and add --emit=llvm-ir
+```
+
+### To prevent the linker from unmangling symbols
+
+Run with:
+
+```
+COLLECT_NO_DEMANGLE=1
+```
+
 ### How to use a custom-build rustc
 
  * Build the stage2 compiler (`rustup toolchain link debug-current build/x86_64-unknown-linux-gnu/stage2`).
@@ -215,6 +287,16 @@ git checkout sync_branch_name
 git merge master
 ```
 
+To send the changes to the rust repo:
+
+```bash
+cd ../rust
+git pull origin master
+git checkout -b subtree-update_cg_gcc_YYYY-MM-DD
+PATH="$HOME/bin:$PATH" ~/bin/git-subtree pull --prefix=compiler/rustc_codegen_gcc/ https://github.com/rust-lang/rustc_codegen_gcc.git master
+git push
+```
+
 TODO: write a script that does the above.
 
 https://rust-lang.zulipchat.com/#narrow/stream/301329-t-devtools/topic/subtree.20madness/near/258877725
@@ -223,20 +305,34 @@ https://rust-lang.zulipchat.com/#narrow/stream/301329-t-devtools/topic/subtree.2
 
 `rustc` needs to be built without `jemalloc` so that `mem-trace` can overload `malloc` since `jemalloc` is linked statically, so a `LD_PRELOAD`-ed library won't a chance to intercept the calls to `malloc`.
 
+### How to generate GIMPLE
+
+If you need to check what gccjit is generating (GIMPLE), then take a look at how to
+generate it in [gimple.md](./doc/gimple.md).
+
 ### How to build a cross-compiling libgccjit
 
 #### Building libgccjit
 
- * Follow these instructions: https://preshing.com/20141119/how-to-build-a-gcc-cross-compiler/ with the following changes:
- * Configure gcc with `../gcc/configure --enable-host-shared --disable-multilib --enable-languages=c,jit,c++ --disable-bootstrap --enable-checking=release --prefix=/opt/m68k-gcc/ --target=m68k-linux --without-headers`.
- * Some shells, like fish, don't define the environment variable `$MACHTYPE`.
- * Add `CFLAGS="-Wno-error=attributes -g -O2"` at the end of the configure command for building glibc (`CFLAGS="-Wno-error=attributes -Wno-error=array-parameter -Wno-error=stringop-overflow -Wno-error=array-bounds -g -O2"` for glibc 2.31, which is useful for Debian).
+ * Follow the instructions on [this repo](https://github.com/cross-cg-gcc-tools/cross-gcc).
 
 #### Configuring rustc_codegen_gcc
 
- * Set `TARGET_TRIPLE="m68k-unknown-linux-gnu"` in config.sh.
- * Since rustc doesn't support this architecture yet, set it back to `TARGET_TRIPLE="mips-unknown-linux-gnu"` (or another target having the same attributes). Alternatively, create a [target specification file](https://book.avr-rust.com/005.1-the-target-specification-json-file.html) (note that the `arch` specified in this file must be supported by the rust compiler).
- * Set `linker='-Clinker=m68k-linux-gcc'`.
+ * Run `./y.sh prepare --cross` so that the sysroot is patched for the cross-compiling case.
  * Set the path to the cross-compiling libgccjit in `gcc_path`.
- * Comment the line: `context.add_command_line_option("-masm=intel");` in src/base.rs.
- * (might not be necessary) Disable the compilation of libstd.so (and possibly libcore.so?).
+ * Make sure you have the linker for your target (for instance `m68k-unknown-linux-gnu-gcc`) in your `$PATH`. Currently, the linker name is hardcoded as being `$TARGET-gcc`. Specify the target when building the sysroot: `./y.sh build --target-triple m68k-unknown-linux-gnu`.
+ * Build your project by specifying the target: `OVERWRITE_TARGET_TRIPLE=m68k-unknown-linux-gnu ../cargo.sh build --target m68k-unknown-linux-gnu`.
+
+If the target is not yet supported by the Rust compiler, create a [target specification file](https://docs.rust-embedded.org/embedonomicon/custom-target.html) (note that the `arch` specified in this file must be supported by the rust compiler).
+Then, you can use it the following way:
+
+ * Add the target specification file using `--target` as an **absolute** path to build the sysroot: `./y.sh build --target-triple m68k-unknown-linux-gnu --target $(pwd)/m68k-unknown-linux-gnu.json`
+ * Build your project by specifying the target specification file: `OVERWRITE_TARGET_TRIPLE=m68k-unknown-linux-gnu ../cargo.sh build --target path/to/m68k-unknown-linux-gnu.json`.
+
+If you get the following error:
+
+```
+/usr/bin/ld: unrecognised emulation mode: m68kelf
+```
+
+Make sure you set `gcc_path` to the install directory.