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Fix OptimizeMax to handle an odd case where one of the max operands

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is another max which folds. This fixes PR7454.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106594 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-06-22 23:07:13 +00:00
parent 0caca3967b
commit caf71ab473
2 changed files with 48 additions and 2 deletions
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5
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -1643,8 +1643,11 @@ ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
NewRHS = Sel->getOperand(1);
else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
NewRHS = Sel->getOperand(2);
else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
NewRHS = SU->getValue();
else
llvm_unreachable("Max doesn't match expected pattern!");
// Max doesn't match expected pattern.
return Cond;
// Determine the new comparison opcode. It may be signed or unsigned,
// and the original comparison may be either equality or inequality.

45
test/CodeGen/X86/optimize-max-3.ll
View File

@ -1,4 +1,4 @@
; RUN: llc < %s -march=x86-64 | FileCheck %s
; RUN: llc < %s -march=x86-64 -asm-verbose=false | FileCheck %s
; LSR's OptimizeMax should eliminate the select (max).
@ -30,3 +30,46 @@ for.body: ; preds = %for.body.preheader,
for.end: ; preds = %for.body, %entry
ret void
}
; In this case, one of the max operands is another max, which folds,
; leaving a two-operand max which doesn't fit the usual pattern.
; OptimizeMax should handle this case.
; PR7454
; CHECK: _Z18GenerateStatusPagei:
; CHECK: jle
; CHECK-NEXT: xorl %edi, %edi
; CHECK-NEXT: align
; CHECK-NEXT: BB1_2:
; CHECK-NEXT: callq
; CHECK-NEXT: incl %ebx
; CHECK-NEXT: cmpl %r14d, %ebx
; CHECK-NEXT: movq %rax, %rdi
; CHECK-NEXT: jl
define void @_Z18GenerateStatusPagei(i32 %jobs_to_display) nounwind {
entry:
%cmp.i = icmp sgt i32 %jobs_to_display, 0 ; <i1> [#uses=1]
%tmp = select i1 %cmp.i, i32 %jobs_to_display, i32 0 ; <i32> [#uses=3]
%cmp8 = icmp sgt i32 %tmp, 0 ; <i1> [#uses=1]
br i1 %cmp8, label %bb.nph, label %for.end
bb.nph: ; preds = %entry
%tmp11 = icmp sgt i32 %tmp, 1 ; <i1> [#uses=1]
%smax = select i1 %tmp11, i32 %tmp, i32 1 ; <i32> [#uses=1]
br label %for.body
for.body: ; preds = %for.body, %bb.nph
%i.010 = phi i32 [ 0, %bb.nph ], [ %inc, %for.body ] ; <i32> [#uses=1]
%it.0.09 = phi float* [ null, %bb.nph ], [ %call.i, %for.body ] ; <float*> [#uses=1]
%call.i = call float* @_ZSt18_Rb_tree_decrementPKSt18_Rb_tree_node_base(float* %it.0.09) ; <float*> [#uses=1]
%inc = add nsw i32 %i.010, 1 ; <i32> [#uses=2]
%exitcond = icmp eq i32 %inc, %smax ; <i1> [#uses=1]
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body, %entry
ret void
}
declare float* @_ZSt18_Rb_tree_decrementPKSt18_Rb_tree_node_base(float*)