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[X86] Make sure SF is updated when optimizing for jg/jge/jl/jle

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This fixes issue #56103.

Reviewed By: mingmingl

Differential Revision: https://reviews.llvm.org/D128122
This commit is contained in:
Phoebe Wang 2022-06-21 08:40:32 +08:00
parent 7c5957aedb
commit edcc68e86f
2 changed files with 70 additions and 0 deletions
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5
llvm/lib/Target/X86/X86InstrInfo.cpp
View File

@ -4462,6 +4462,11 @@ bool X86InstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, Register SrcReg,
return false;
case X86::COND_G: case X86::COND_GE:
case X86::COND_L: case X86::COND_LE:
// If SF is used, but the instruction doesn't update the SF, then we
// can't do the optimization.
if (NoSignFlag)
return false;
LLVM_FALLTHROUGH;
case X86::COND_O: case X86::COND_NO:
// If OF is used, the instruction needs to clear it like CmpZero does.
if (!ClearsOverflowFlag)

65
llvm/test/CodeGen/X86/pr56103.ll Normal file
View File

@ -0,0 +1,65 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-linux-generic | FileCheck %s
@e = global i16 0, align 2
@a = global i32 0, align 4
@c = global i32 0, align 4
@b = global i64 0, align 8
; Check the test instruction won't be optimizated by peephole opt.
define dso_local i32 @main() nounwind {
; CHECK-LABEL: main:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: pushq %rax
; CHECK-NEXT: movq e@GOTPCREL(%rip), %rax
; CHECK-NEXT: movw $1, (%rax)
; CHECK-NEXT: movq b@GOTPCREL(%rip), %rax
; CHECK-NEXT: movq $1, (%rax)
; CHECK-NEXT: movq a@GOTPCREL(%rip), %rax
; CHECK-NEXT: movl (%rax), %ecx
; CHECK-NEXT: movl $-2, %eax
; CHECK-NEXT: sarl %cl, %eax
; CHECK-NEXT: movq c@GOTPCREL(%rip), %rdx
; CHECK-NEXT: movl (%rdx), %edx
; CHECK-NEXT: decl %edx
; CHECK-NEXT: movzwl %ax, %eax
; CHECK-NEXT: decl %eax
; CHECK-NEXT: xorl %edx, %eax
; CHECK-NEXT: notl %ecx
; CHECK-NEXT: andl %eax, %ecx
; CHECK-NEXT: testq %rcx, %rcx
; CHECK-NEXT: jle .LBB0_2
; CHECK-NEXT: # %bb.1: # %if.end
; CHECK-NEXT: xorl %eax, %eax
; CHECK-NEXT: popq %rcx
; CHECK-NEXT: retq
; CHECK-NEXT: .LBB0_2: # %if.then
; CHECK-NEXT: callq abort@PLT
entry:
store i16 1, ptr @e, align 2
store i64 1, ptr @b, align 8
%0 = load i32, ptr @a, align 4
%shr = ashr i32 -2, %0
%1 = load i32, ptr @c, align 4
%sub = add i32 %1, -1
%conv2 = zext i32 %sub to i64
%2 = and i32 %shr, 65535
%conv3 = zext i32 %2 to i64
%sub4 = add nsw i64 %conv3, -1
%xor = xor i64 %sub4, %conv2
%neg5 = xor i32 %0, -1
%conv6 = sext i32 %neg5 to i64
%and = and i64 %xor, %conv6
%cmp = icmp slt i64 %and, 1
br i1 %cmp, label %if.then, label %if.end
if.then: ; preds = %entry
call void @abort() #2
unreachable
if.end: ; preds = %entry
ret i32 0
}
declare void @abort()