[llvm-branch-commits] [llvm] 88e17a8 - [SelectionDAG] Remove unused FP constant in getNegatedExpression

[Hans Wennborg via llvm-branch-commits]

Author: Qiu Chaofan
Date: 2020-09-15T13:42:41+02:00
New Revision: 88e17a8e9b49bfbcfc1fa70f867b5b56a7a64fc7

URL: https://github.com/llvm/llvm-project/commit/88e17a8e9b49bfbcfc1fa70f867b5b56a7a64fc7
DIFF: https://github.com/llvm/llvm-project/commit/88e17a8e9b49bfbcfc1fa70f867b5b56a7a64fc7.diff

LOG: [SelectionDAG] Remove unused FP constant in getNegatedExpression

960cbc53 immediately removes nodes that won't be used to avoid
compilation time explosion. This patch adds the removal to constants to
fix PR47517.

Reviewed By: RKSimon, steven.zhang

Differential Revision: https://reviews.llvm.org/D87614

(cherry picked from commit 2508ef014e8b01006de4e5ee6fd451d1f68d550f)

Added: 
    llvm/test/CodeGen/X86/pr47517.ll

Modified: 
    llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 819e608c6896..4ebb99c97841 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5751,8 +5751,10 @@ 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())
+    if (!Op.hasOneUse() && CFP.use_empty()) {
+      RemoveDeadNode(CFP);
       break;
+    }
     Cost = NegatibleCost::Neutral;
     return CFP;
   }

diff  --git a/llvm/test/CodeGen/X86/pr47517.ll b/llvm/test/CodeGen/X86/pr47517.ll
new file mode 100644
index 000000000000..6b508acf15dd
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pr47517.ll
@@ -0,0 +1,28 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple x86_64 < %s | FileCheck %s
+
+; To ensure unused floating point constant is removed in negation
+define float @test(float %src, float* %p) {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    movq $0, (%rdi)
+; CHECK-NEXT:    xorps %xmm0, %xmm0
+; CHECK-NEXT:    retq
+entry:
+  %a0 = getelementptr inbounds float, float* %p, i32 0
+  %a1 = getelementptr inbounds float, float* %p, i32 1
+  store float 0.000000e+00, float* %a0
+  store float 0.000000e+00, float* %a1
+  %zero = load float, float* %a0
+  %fmul1 = fmul fast float %zero, %src
+  %fadd1 = fadd fast float %fmul1, %zero
+  %fmul2 = fmul fast float %fadd1, 2.000000e+00
+  %fmul3 = fmul fast float %fmul2, %fmul2
+  %fmul4 = fmul fast float %fmul2, 2.000000e+00
+  %fadd2 = fadd fast float %fmul4, -3.000000e+00
+  %fmul5 = fmul fast float %fadd2, %fmul2
+  %fadd3 = fadd fast float %fmul2, %src
+  %fadd4 = fadd fast float %fadd3, %fmul5
+  %fmul6 = fmul fast float %fmul3, %fadd4
+  ret float %fmul6
+}