2024-02-22 06:10:29 -06:00
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//@ compile-flags: -O
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//@ only-x86_64
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Re-optimize `Layout::array`
This way it's one check instead of two, so hopefully it'll be better
Nightly:
```
layout_array_i32:
movq %rdi, %rax
movl $4, %ecx
mulq %rcx
jo .LBB1_2
movabsq $9223372036854775805, %rcx
cmpq %rcx, %rax
jae .LBB1_2
movl $4, %edx
retq
.LBB1_2:
…
```
This PR:
```
movq %rcx, %rax
shrq $61, %rax
jne .LBB2_1
shlq $2, %rcx
movl $4, %edx
movq %rcx, %rax
retq
.LBB2_1:
…
```
2022-07-12 05:03:19 -05:00
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#![crate_type = "lib"]
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use std::alloc::Layout;
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type RGB48 = [u16; 3];
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// CHECK-LABEL: @layout_array_rgb48
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#[no_mangle]
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pub fn layout_array_rgb48(n: usize) -> Layout {
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// CHECK-NOT: llvm.umul.with.overflow.i64
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// CHECK: icmp ugt i64 %n, 1537228672809129301
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// CHECK-NOT: llvm.umul.with.overflow.i64
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// CHECK: mul nuw nsw i64 %n, 6
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// CHECK-NOT: llvm.umul.with.overflow.i64
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Layout::array::<RGB48>(n).unwrap()
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}
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// CHECK-LABEL: @layout_array_i32
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#[no_mangle]
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pub fn layout_array_i32(n: usize) -> Layout {
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// CHECK-NOT: llvm.umul.with.overflow.i64
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// CHECK: icmp ugt i64 %n, 2305843009213693951
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// CHECK-NOT: llvm.umul.with.overflow.i64
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// CHECK: shl nuw nsw i64 %n, 2
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// CHECK-NOT: llvm.umul.with.overflow.i64
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Layout::array::<i32>(n).unwrap()
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}
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