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[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
This commit is contained in:
Qiu Chaofan 2020-09-15 17:59:10 +08:00
parent 5f13d6c1ee
commit 2508ef014e
2 changed files with 31 additions and 1 deletions
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4
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
View File

@ -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;
}

28
llvm/test/CodeGen/X86/pr47517.ll Normal file
View File

@ -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
}