8523fb96a6
Given a select_cc producing a constant and a invertion of the constant for a comparison more than zero, we can produce an xor with ashr instead, which produces smaller code. The ashr either sets all bits or clear all bits depending on if the value is negative. This is then xor'd with the constant to optionally negate the value. https://alive2.llvm.org/ce/z/DTFaBZ This includes a OneUseCheck on the Cmp, which seems to make thinks a little worse and will be removed in a followup. Differential Revision: https://reviews.llvm.org/D109149
30 lines
950 B
LLVM
30 lines
950 B
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc < %s -mtriple=i386-unknown-linux-gnu -mcpu=corei7-avx -enable-misched=false | FileCheck %s
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define i64 @main(i1 %tobool1) nounwind {
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; CHECK-LABEL: main:
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; CHECK: # %bb.0: # %entry
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; CHECK-NEXT: pushl %esi
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; CHECK-NEXT: testb $1, {{[0-9]+}}(%esp)
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; CHECK-NEXT: movl $-12, %eax
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; CHECK-NEXT: movl $-1, %ecx
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; CHECK-NEXT: cmovel %ecx, %eax
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; CHECK-NEXT: xorl %edx, %edx
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; CHECK-NEXT: movl %eax, %esi
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; CHECK-NEXT: addl $-1, %esi
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; CHECK-NEXT: adcl $-1, %ecx
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; CHECK-NEXT: cmovsl %edx, %eax
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; CHECK-NEXT: xorl %edx, %edx
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; CHECK-NEXT: popl %esi
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; CHECK-NEXT: retl
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entry:
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%0 = zext i1 %tobool1 to i32
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%. = xor i32 %0, 1
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%.21 = select i1 %tobool1, i32 -12, i32 -1
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%conv = sext i32 %.21 to i64
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%1 = add i64 %conv, -1
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%cmp10 = icmp slt i64 %1, 0
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%sub17 = select i1 %cmp10, i64 0, i64 %conv
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ret i64 %sub17
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}
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