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Use load-store instead of memcpy for short integer arrays

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This commit is contained in:
Scott McMurray 2023-05-26 03:32:22 -07:00
parent cce0b52e7b
commit e1b020df9f
8 changed files with 136 additions and 16 deletions
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25
tests/codegen/swap-small-types.rs
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@ -1,4 +1,4 @@
// compile-flags: -O
// compile-flags: -O -Z merge-functions=disabled
// only-x86_64
// ignore-debug: the debug assertions get in the way
@ -12,13 +12,10 @@ type RGB48 = [u16; 3];
#[no_mangle]
pub fn swap_rgb48_manually(x: &mut RGB48, y: &mut RGB48) {
// CHECK-NOT: alloca
// CHECK: %temp = alloca [3 x i16]
// CHECK-NOT: alloca
// CHECK-NOT: call void @llvm.memcpy
// CHECK: call void @llvm.memcpy.{{.+}}({{.+}} %temp, {{.+}} %x, {{.+}} 6, {{.+}})
// CHECK: call void @llvm.memcpy.{{.+}}({{.+}} %x, {{.+}} %y, {{.+}} 6, {{.+}})
// CHECK: call void @llvm.memcpy.{{.+}}({{.+}} %y, {{.+}} %temp, {{.+}} 6, {{.+}})
// CHECK-NOT: call void @llvm.memcpy
// CHECK: %[[TEMP0:.+]] = load <3 x i16>, ptr %x, align 2
// CHECK: %[[TEMP1:.+]] = load <3 x i16>, ptr %y, align 2
// CHECK: store <3 x i16> %[[TEMP1]], ptr %x, align 2
// CHECK: store <3 x i16> %[[TEMP0]], ptr %y, align 2
let temp = *x;
*x = *y;
@ -28,13 +25,11 @@ pub fn swap_rgb48_manually(x: &mut RGB48, y: &mut RGB48) {
// CHECK-LABEL: @swap_rgb48
#[no_mangle]
pub fn swap_rgb48(x: &mut RGB48, y: &mut RGB48) {
// FIXME MIR inlining messes up LLVM optimizations.
// If these checks start failing, please update this test.
// CHECK: alloca [3 x i16]
// CHECK: call void @llvm.memcpy
// WOULD-CHECK-NOT: alloca
// WOULD-CHECK: load i48
// WOULD-CHECK: store i48
// CHECK-NOT: alloca
// CHECK: load <3 x i16>
// CHECK: load <3 x i16>
// CHECK: store <3 x i16>
// CHECK: store <3 x i16>
swap(x, y)
}