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InstCombine: Turn (x != 0 & x <u C) into the canonical range check form (x-1 <u C-1)

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llvm-svn: 219585
This commit is contained in:
Benjamin Kramer 2014-10-12 14:02:34 +00:00
parent 3b8f17ae65
commit 8581af15aa
2 changed files with 13 additions and 0 deletions
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2
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -930,6 +930,8 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
case ICmpInst::ICMP_ULT:
if (LHSCst == SubOne(RHSCst)) // (X != 13 & X u< 14) -> X < 13
return Builder->CreateICmpULT(Val, LHSCst);
if (LHSCst->isNullValue()) // (X != 0 & X u< 14) -> X-1 u< 13
return InsertRangeTest(Val, AddOne(LHSCst), RHSCst, false, true);
break; // (X != 13 & X u< 15) -> no change
case ICmpInst::ICMP_SLT:
if (LHSCst == SubOne(RHSCst)) // (X != 13 & X s< 14) -> X < 13

11
test/Transforms/InstCombine/and2.ll
View File

@ -66,3 +66,14 @@ define i1 @test7(i32 %i, i1 %b) {
%and2 = and i1 %and1, %cmp2
ret i1 %and2
}
define i1 @test8(i32 %i) {
; CHECK-LABEL: @test8(
; CHECK-NEXT: [[DEC:%.*]] = add i32 %i, -1
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[DEC]], 13
; CHECK-NEXT: ret i1 [[CMP]]
%cmp1 = icmp ne i32 %i, 0
%cmp2 = icmp ult i32 %i, 14
%cond = and i1 %cmp1, %cmp2
ret i1 %cond
}