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Add a new compare_bytes intrinsic instead of calling memcmp directly

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This commit is contained in:
Scott McMurray 2023-08-02 12:45:52 -07:00
parent 85fbb57149
commit 502af03445
17 changed files with 267 additions and 22 deletions
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3
compiler/rustc_codegen_llvm/src/context.rs
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@ -891,7 +891,8 @@ impl<'ll> CodegenCx<'ll, '_> {
ifn!("llvm.prefetch", fn(ptr, t_i32, t_i32, t_i32) -> void);
// This isn't an "LLVM intrinsic", but LLVM's optimization passes
// recognize it like one and we assume it exists in `core::slice::cmp`
// recognize it like one (including turning it into `bcmp` sometimes)
// and we use it to implement intrinsics like `raw_eq` and `compare_bytes`
match self.sess().target.arch.as_ref() {
"avr" | "msp430" => ifn!("memcmp", fn(ptr, ptr, t_isize) -> t_i16),
_ => ifn!("memcmp", fn(ptr, ptr, t_isize) -> t_i32),

9
compiler/rustc_codegen_llvm/src/intrinsic.rs
View file

@ -329,6 +329,15 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
}
}
sym::compare_bytes => {
let cmp = self.call_intrinsic(
"memcmp",
&[args[0].immediate(), args[1].immediate(), args[2].immediate()],
);
// Some targets have `memcmp` returning `i16`, but the intrinsic is always `i32`.
self.sext(cmp, self.type_ix(32))
}
sym::black_box => {
args[0].val.store(self, result);
let result_val_span = [result.llval];