Author: Qiu Chaofan Date: 2020-10-06T16:04:19+02:00 New Revision: 121babae56e9f08acedf3d6d44757e35556d0a37
URL: https://github.com/llvm/llvm-project/commit/121babae56e9f08acedf3d6d44757e35556d0a37 DIFF: https://github.com/llvm/llvm-project/commit/121babae56e9f08acedf3d6d44757e35556d0a37.diff LOG: [SelectionDAG] Don't remove unused negated constant immediately This reverts partial of a2fb5446 (actually, 2508ef01) about removing negated FP constant immediately if it has no uses. However, as discussed in bug 47517, there're cases when NegX is folded into constant from other places while NegY is removed by that line of code and NegX is equal to NegY. In these cases, NegX is deleted before used and crash happens. So revert the code and add necessary test case. (cherry picked from commit b326d4ff946d2061a566a3fcce9f33b484759fe0) Added: Modified: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp llvm/test/CodeGen/X86/pr47517.ll Removed: ################################################################################ diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp index 64af293caf9ea..8b3e6189a07f8 100644 --- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -5751,10 +5751,8 @@ SDValue TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG, // If we already have the use of the negated floating constant, it is free // to negate it even it has multiple uses. - if (!Op.hasOneUse() && CFP.use_empty()) { - RemoveDeadNode(CFP); + if (!Op.hasOneUse() && CFP.use_empty()) break; - } Cost = NegatibleCost::Neutral; return CFP; } diff --git a/llvm/test/CodeGen/X86/pr47517.ll b/llvm/test/CodeGen/X86/pr47517.ll index 5672fbc69a41d..afc27b49ab2a4 100644 --- a/llvm/test/CodeGen/X86/pr47517.ll +++ b/llvm/test/CodeGen/X86/pr47517.ll @@ -26,3 +26,16 @@ entry: %fmul6 = fmul fast float %fmul3, %fadd4 ret float %fmul6 } + +; To ensure negated result will not be removed when NegX=NegY and +; NegX is needed +define float @test2(float %x, float %y) { + %add = fadd fast float %x, 750.0 + %sub = fsub fast float %x, %add + %mul = fmul fast float %sub, %sub + %mul2 = fmul fast float %mul, %sub + %add2 = fadd fast float %mul2, 1.0 + %add3 = fadd fast float %mul2, %add2 + %mul3 = fmul fast float %y, %add3 + ret float %mul3 +} _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
