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InstCombine: Try harder to combine icmp instructions

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consider: (and (icmp X, Y), (and Z, (icmp A, B)))
It may be possible to combine (icmp X, Y) with (icmp A, B).
If we successfully combine, create an 'and' instruction with Z.

This fixes PR20814.

N.B. There is room for improvement after this change but I'm not
convinced it's worth chasing yet.

llvm-svn: 216814
This commit is contained in:
David Majnemer 2014-08-30 06:18:20 +00:00
parent 0421e5dc75
commit 5cf3ee996f
2 changed files with 38 additions and 4 deletions
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28
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1101,7 +1101,6 @@ Value *InstCombiner::FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS) {
return nullptr;
}
Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
bool Changed = SimplifyAssociativeOrCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
@ -1307,11 +1306,34 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
return BinaryOperator::CreateAnd(A, B);
}
if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1))
if (ICmpInst *LHS = dyn_cast<ICmpInst>(Op0))
{
ICmpInst *LHS = dyn_cast<ICmpInst>(Op0);
ICmpInst *RHS = dyn_cast<ICmpInst>(Op1);
if (LHS && RHS)
if (Value *Res = FoldAndOfICmps(LHS, RHS))
return ReplaceInstUsesWith(I, Res);
// TODO: Make this recursive; it's a little tricky because an arbitrary
// number of 'and' instructions might have to be created.
Value *X, *Y;
if (LHS && match(Op1, m_OneUse(m_And(m_Value(X), m_Value(Y))))) {
if (auto *Cmp = dyn_cast<ICmpInst>(X))
if (Value *Res = FoldAndOfICmps(LHS, Cmp))
return ReplaceInstUsesWith(I, Builder->CreateAnd(Res, Y));
if (auto *Cmp = dyn_cast<ICmpInst>(Y))
if (Value *Res = FoldAndOfICmps(LHS, Cmp))
return ReplaceInstUsesWith(I, Builder->CreateAnd(Res, X));
}
if (RHS && match(Op0, m_OneUse(m_And(m_Value(X), m_Value(Y))))) {
if (auto *Cmp = dyn_cast<ICmpInst>(X))
if (Value *Res = FoldAndOfICmps(Cmp, RHS))
return ReplaceInstUsesWith(I, Builder->CreateAnd(Res, Y));
if (auto *Cmp = dyn_cast<ICmpInst>(Y))
if (Value *Res = FoldAndOfICmps(Cmp, RHS))
return ReplaceInstUsesWith(I, Builder->CreateAnd(Res, X));
}
}
// If and'ing two fcmp, try combine them into one.
if (FCmpInst *LHS = dyn_cast<FCmpInst>(I.getOperand(0)))
if (FCmpInst *RHS = dyn_cast<FCmpInst>(I.getOperand(1)))

14
test/Transforms/InstCombine/and2.ll
View File

@ -45,7 +45,7 @@ define <4 x i32> @test5(<4 x i32> %A) {
; Check that we combine "if x!=0 && x!=-1" into "if x+1u>1"
define i32 @test6(i64 %x) nounwind {
; CHECK: @test6
; CHECK-LABEL: @test6(
; CHECK-NEXT: add i64 %x, 1
; CHECK-NEXT: icmp ugt i64 %x.off, 1
%cmp1 = icmp ne i64 %x, -1
@ -54,3 +54,15 @@ define i32 @test6(i64 %x) nounwind {
%land.ext = zext i1 %.cmp1 to i32
ret i32 %land.ext
}
define i1 @test7(i32 %i, i1 %b) {
; CHECK-LABEL: @test7(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 %i, 0
; CHECK-NEXT: [[AND:%.*]] = and i1 [[CMP]], %b
; CHECK-NEXT: ret i1 [[AND]]
%cmp1 = icmp slt i32 %i, 1
%cmp2 = icmp sgt i32 %i, -1
%and1 = and i1 %cmp1, %b
%and2 = and i1 %and1, %cmp2
ret i1 %and2
}