bjoernager/rust
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Stop generating allocas+memcmp for simple array equality

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This commit is contained in:
Scott McMurray 2021-05-30 10:25:41 -07:00
parent d05eafae2f
commit 2456495a26
12 changed files with 238 additions and 4 deletions
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5
compiler/rustc_codegen_llvm/src/context.rs
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@ -500,6 +500,7 @@ impl CodegenCx<'b, 'tcx> {
let t_i32 = self.type_i32();
let t_i64 = self.type_i64();
let t_i128 = self.type_i128();
let t_isize = self.type_isize();
let t_f32 = self.type_f32();
let t_f64 = self.type_f64();
@ -712,6 +713,10 @@ impl CodegenCx<'b, 'tcx> {
ifn!("llvm.assume", fn(i1) -> void);
ifn!("llvm.prefetch", fn(i8p, 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`
ifn!("memcmp", fn(i8p, i8p, t_isize) -> t_i32);
// variadic intrinsics
ifn!("llvm.va_start", fn(i8p) -> void);
ifn!("llvm.va_end", fn(i8p) -> void);

26
compiler/rustc_codegen_llvm/src/intrinsic.rs
View file

@ -296,6 +296,32 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
}
}
sym::raw_eq => {
let tp_ty = substs.type_at(0);
let (size, align) = self.size_and_align_of(tp_ty);
let a = args[0].immediate();
let b = args[1].immediate();
if size.bytes() == 0 {
self.const_bool(true)
} else if size > self.data_layout().pointer_size * 4 {
let i8p_ty = self.type_i8p();
let a_ptr = self.bitcast(a, i8p_ty);
let b_ptr = self.bitcast(b, i8p_ty);
let n = self.const_usize(size.bytes());
let llfn = self.get_intrinsic("memcmp");
let cmp = self.call(llfn, &[a_ptr, b_ptr, n], None);
self.icmp(IntPredicate::IntEQ, cmp, self.const_i32(0))
} else {
let integer_ty = self.type_ix(size.bits());
let ptr_ty = self.type_ptr_to(integer_ty);
let a_ptr = self.bitcast(a, ptr_ty);
let a_val = self.load(a_ptr, align);
let b_ptr = self.bitcast(b, ptr_ty);
let b_val = self.load(b_ptr, align);
self.icmp(IntPredicate::IntEQ, a_val, b_val)
}
}
_ if name_str.starts_with("simd_") => {
match generic_simd_intrinsic(self, name, callee_ty, args, ret_ty, llret_ty, span) {
Ok(llval) => llval,