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https://github.com/c64scene-ar/llvm-6502.git
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307473dec0
This patch will optimize abs(x-y) FROM sub, movs, rsbmi TO subs, rsbmi For abs, we will use cmp instead of movs. This is necessary because we already have an existing peephole pass which optimizes away cmp following sub. rdar: 11633193 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158551 91177308-0d34-0410-b5e6-96231b3b80d8
35 lines
780 B
LLVM
35 lines
780 B
LLVM
; RUN: llc < %s -march=arm -mattr=+v4t | FileCheck %s
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;; Integer absolute value, should produce something as good as: ARM:
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;; movs r0, r0
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;; rsbmi r0, r0, #0
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;; bx lr
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define i32 @test(i32 %a) {
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%tmp1neg = sub i32 0, %a
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%b = icmp sgt i32 %a, -1
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%abs = select i1 %b, i32 %a, i32 %tmp1neg
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ret i32 %abs
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; CHECK: cmp
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; CHECK: rsbmi r0, r0, #0
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; CHECK: bx lr
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}
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; rdar://11633193
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;; 3 instructions will be generated for abs(a-b):
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;; subs
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;; rsbmi
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;; bx
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define i32 @test2(i32 %a, i32 %b) nounwind readnone ssp {
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entry:
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; CHECK: test2
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; CHECK: subs
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; CHECK-NEXT: rsbmi
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; CHECK-NEXT: bx
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%sub = sub nsw i32 %a, %b
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%cmp = icmp sgt i32 %sub, -1
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%sub1 = sub nsw i32 0, %sub
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%cond = select i1 %cmp, i32 %sub, i32 %sub1
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ret i32 %cond
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}
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