diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 4 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/fsub.ll | 14 |
2 files changed, 17 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 1e4c38c4c84..97ad92d2aad 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1795,8 +1795,10 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) { return NV; // X - C --> X + (-C) + // But don't transform constant expressions because there's an inverse fold + // for X + (-Y) --> X - Y. Constant *C; - if (match(Op1, m_Constant(C))) + if (match(Op1, m_Constant(C)) && !isa<ConstantExpr>(Op1)) return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &I); // X - (-Y) --> X + Y diff --git a/llvm/test/Transforms/InstCombine/fsub.ll b/llvm/test/Transforms/InstCombine/fsub.ll index 9ce73084f79..22295490cc6 100644 --- a/llvm/test/Transforms/InstCombine/fsub.ll +++ b/llvm/test/Transforms/InstCombine/fsub.ll @@ -242,3 +242,17 @@ define float @neg_trunc_op1_extra_uses(double %a, float %b) { ret float %t3 } +; Don't negate a constant expression to form fadd and induce infinite looping: +; https://bugs.llvm.org/show_bug.cgi?id=37605 + +@b = external global i16, align 1 + +define float @PR37605(float %conv) { +; CHECK-LABEL: @PR37605( +; CHECK-NEXT: [[SUB:%.*]] = fsub float [[CONV:%.*]], bitcast (i32 ptrtoint (i16* @b to i32) to float) +; CHECK-NEXT: ret float [[SUB]] +; + %sub = fsub float %conv, bitcast (i32 ptrtoint (i16* @b to i32) to float) + ret float %sub +} + |
