[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

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 3446ee0..749a5e8 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5773,8 +5773,10 @@ 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 (file)
index 0000000..6b508ac
--- /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
+}