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InstCombine: Simplify if(x!=0 && x!=-1).

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When both constants are positive or both constants are negative,
InstCombine already simplifies comparisons like this, but when
it's exactly zero and -1, the operand sorting ends up reversed
and the pattern fails to match. Handle that special case.

Follow up for rdar://14689217

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188512 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach 2013-08-16 00:15:20 +00:00
parent da44b4f68b
commit 4658ce9c1f
2 changed files with 18 additions and 1 deletions
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7
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -849,10 +849,15 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
case ICmpInst::ICMP_SGT: // (X != 13 & X s> 15) -> X s> 15
return RHS;
case ICmpInst::ICMP_NE:
// Special case to get the ordering right when the values wrap around
// zero.
if (LHSCst->getValue() == 0 && RHSCst->getValue() == -1)
std::swap(LHSCst, RHSCst);
if (LHSCst == SubOne(RHSCst)){// (X != 13 & X != 14) -> X-13 >u 1
Constant *AddCST = ConstantExpr::getNeg(LHSCst);
Value *Add = Builder->CreateAdd(Val, AddCST, Val->getName()+".off");
return Builder->CreateICmpUGT(Add, ConstantInt::get(Add->getType(), 1));
return Builder->CreateICmpUGT(Add, ConstantInt::get(Add->getType(), 1),
Val->getName()+".cmp");
}
break; // (X != 13 & X != 15) -> no change
}

12
test/Transforms/InstCombine/and2.ll
View File

@ -42,3 +42,15 @@ define <4 x i32> @test5(<4 x i32> %A) {
%2 = and <4 x i32> <i32 1, i32 2, i32 3, i32 4>, %1
ret <4 x i32> %2
}
; Check that we combine "if x!=0 && x!=-1" into "if x+1u>1"
define i32 @test6(i64 %x) nounwind {
; CHECK: @test6
; CHECK-NEXT: add i64 %x, 1
; CHECK-NEXT: icmp ugt i64 %x.off, 1
%cmp1 = icmp ne i64 %x, -1
%not.cmp = icmp ne i64 %x, 0
%.cmp1 = and i1 %cmp1, %not.cmp
%land.ext = zext i1 %.cmp1 to i32
ret i32 %land.ext
}