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Adjust the threshold to look at the ABI, not just the size

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This commit is contained in:
Scott McMurray 2021-06-02 23:35:30 -07:00
parent 6444f24a29
commit 07fb5ee78f
2 changed files with 36 additions and 12 deletions
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36
compiler/rustc_codegen_llvm/src/intrinsic.rs
View File

@ -297,28 +297,40 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
}
sym::raw_eq => {
use abi::Abi::*;
let tp_ty = substs.type_at(0);
let (size, align) = self.size_and_align_of(tp_ty);
let layout = self.layout_of(tp_ty).layout;
let use_integer_compare = match layout.abi {
Scalar(_) | ScalarPair(_, _) => true,
Uninhabited | Vector { .. } => false,
Aggregate { .. } => {
// For rusty ABIs, small aggregates are actually passed
// as `RegKind::Integer` (see `FnAbi::adjust_for_abi`),
// so we re-use that same threshold here.
layout.size <= self.data_layout().pointer_size * 2
}
};
let a = args[0].immediate();
let b = args[1].immediate();
if size.bytes() == 0 {
if layout.size.bytes() == 0 {
self.const_bool(true)
} else if size > self.data_layout().pointer_size * 4 {
} else if use_integer_compare {
let integer_ty = self.type_ix(layout.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, layout.align.abi);
let b_ptr = self.bitcast(b, ptr_ty);
let b_val = self.load(b_ptr, layout.align.abi);
self.icmp(IntPredicate::IntEQ, a_val, b_val)
} else {
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 n = self.const_usize(layout.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)
}
}

12
src/test/codegen/array-equality.rs
View File

@ -23,6 +23,18 @@ pub fn array_eq_ref(a: &[u16; 6], b: &[u16; 6]) -> bool {
a == b
}
// CHECK-LABEL: @array_eq_value_still_passed_by_pointer
#[no_mangle]
pub fn array_eq_value_still_passed_by_pointer(a: [u16; 9], b: [u16; 9]) -> bool {
// CHECK-NEXT: start:
// CHECK-NEXT: bitcast
// CHECK-NEXT: bitcast
// CHECK-NEXT: %[[CMP:.+]] = tail call i32 @{{bcmp|memcmp}}(i8* nonnull dereferenceable(18) %{{.+}}, i8* nonnull dereferenceable(18) %{{.+}}, i64 18)
// CHECK-NEXT: %[[EQ:.+]] = icmp eq i32 %[[CMP]], 0
// CHECK-NEXT: ret i1 %[[EQ]]
a == b
}
// CHECK-LABEL: @array_eq_long
#[no_mangle]
pub fn array_eq_long(a: &[u16; 1234], b: &[u16; 1234]) -> bool {