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author | Eli Friedman <eli.friedman@gmail.com> | 2011-09-19 21:58:15 +0000 |
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committer | Eli Friedman <eli.friedman@gmail.com> | 2011-09-19 21:58:15 +0000 |
commit | c6b8ba86738cb6187835e440f2baafaa24dea0b2 (patch) | |
tree | 4b308426bc45ed2e7470f73bcbe17c89dea5ae84 | |
parent | 1494c496e2827f991f75eae4acf8f7bf9952abdd (diff) | |
download | llvm-c6b8ba86738cb6187835e440f2baafaa24dea0b2.tar.gz llvm-c6b8ba86738cb6187835e440f2baafaa24dea0b2.tar.bz2 llvm-c6b8ba86738cb6187835e440f2baafaa24dea0b2.tar.xz |
Fix an infinite loop where a transform in InstCombiner::visitAnd claims a construct is changed when it is not. (See included testcase.)
Patch by Xiaoyi Guo.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140072 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 43 | ||||
-rw-r--r-- | test/Transforms/InstCombine/and2.ll | 7 |
2 files changed, 29 insertions, 21 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 32920fabc3..d16f8ce821 100644 --- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -1174,30 +1174,31 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) { ((A == C && B == D) || (A == D && B == C))) return BinaryOperator::CreateXor(A, B); - if (Op0->hasOneUse() && - match(Op0, m_Xor(m_Value(A), m_Value(B)))) { - if (A == Op1) { // (A^B)&A -> A&(A^B) - I.swapOperands(); // Simplify below - std::swap(Op0, Op1); - } else if (B == Op1) { // (A^B)&B -> B&(B^A) - cast<BinaryOperator>(Op0)->swapOperands(); - I.swapOperands(); // Simplify below - std::swap(Op0, Op1); + // A&(A^B) => A & ~B + { + Value *tmpOp0 = Op0; + Value *tmpOp1 = Op1; + if (Op0->hasOneUse() && + match(Op0, m_Xor(m_Value(A), m_Value(B)))) { + if (A == Op1 || B == Op1 ) { + tmpOp1 = Op0; + tmpOp0 = Op1; + // Simplify below + } } - } - if (Op1->hasOneUse() && - match(Op1, m_Xor(m_Value(A), m_Value(B)))) { - if (B == Op0) { // B&(A^B) -> B&(B^A) - cast<BinaryOperator>(Op1)->swapOperands(); - std::swap(A, B); + if (tmpOp1->hasOneUse() && + match(tmpOp1, m_Xor(m_Value(A), m_Value(B)))) { + if (B == tmpOp0) { + std::swap(A, B); + } + // Notice that the patten (A&(~B)) is actually (A&(-1^B)), so if + // A is originally -1 (or a vector of -1 and undefs), then we enter + // an endless loop. By checking that A is non-constant we ensure that + // we will never get to the loop. + if (A == tmpOp0 && !isa<Constant>(A)) // A&(A^B) -> A & ~B + return BinaryOperator::CreateAnd(A, Builder->CreateNot(B, "tmp")); } - // Notice that the patten (A&(~B)) is actually (A&(-1^B)), so if - // A is originally -1 (or a vector of -1 and undefs), then we enter - // an endless loop. By checking that A is non-constant we ensure that - // we will never get to the loop. - if (A == Op0 && !isa<Constant>(A)) // A&(A^B) -> A & ~B - return BinaryOperator::CreateAnd(A, Builder->CreateNot(B, "tmp")); } // (A&((~A)|B)) -> A&B diff --git a/test/Transforms/InstCombine/and2.ll b/test/Transforms/InstCombine/and2.ll index a8881522ea..531aedb668 100644 --- a/test/Transforms/InstCombine/and2.ll +++ b/test/Transforms/InstCombine/and2.ll @@ -35,3 +35,10 @@ define i1 @test4(i32 %X) { ; CHECK: @test4 ; CHECK-NEXT: ret i1 false } + +; Make sure we don't go into an infinite loop with this test +define <4 x i32> @test5(<4 x i32> %A) { + %1 = xor <4 x i32> %A, <i32 1, i32 2, i32 3, i32 4> + %2 = and <4 x i32> <i32 1, i32 2, i32 3, i32 4>, %1 + ret <4 x i32> %2 +} |