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[AMDGPU] Avoid DAG combining assert with fneg(fadd(A,0)) 

fneg combining attempts to turn it into fadd(fneg(A), fneg(0)), but
creating the new fadd folds to just fneg(A). When A has multiple uses,
this confuses it and you get an assert. Fixed.

Differential Revision: https://reviews.llvm.org/D60633

Change-Id: I0ddc9b7286abe78edc0cd8d734fdeb05ff09821c
llvm-svn: 358640
This commit is contained in:
Tim Renouf 2019-04-18 05:27:01 +00:00
parent 6263365b08
commit 7c55c8d8c3
2 changed files with 32 additions and 0 deletions
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10
llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
View File

@ -3692,6 +3692,8 @@ SDValue AMDGPUTargetLowering::performFNegCombine(SDNode *N,
RHS = RHS.getOperand(0);
SDValue Res = DAG.getNode(ISD::FADD, SL, VT, LHS, RHS, N0->getFlags());
if (Res.getOpcode() != ISD::FADD)
return SDValue(); // Op got folded away.
if (!N0.hasOneUse())
DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
return Res;
@ -3711,6 +3713,8 @@ SDValue AMDGPUTargetLowering::performFNegCombine(SDNode *N,
RHS = DAG.getNode(ISD::FNEG, SL, VT, RHS);
SDValue Res = DAG.getNode(Opc, SL, VT, LHS, RHS, N0->getFlags());
if (Res.getOpcode() != Opc)
return SDValue(); // Op got folded away.
if (!N0.hasOneUse())
DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
return Res;
@ -3738,6 +3742,8 @@ SDValue AMDGPUTargetLowering::performFNegCombine(SDNode *N,
RHS = RHS.getOperand(0);
SDValue Res = DAG.getNode(Opc, SL, VT, LHS, MHS, RHS);
if (Res.getOpcode() != Opc)
return SDValue(); // Op got folded away.
if (!N0.hasOneUse())
DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
return Res;
@ -3766,6 +3772,8 @@ SDValue AMDGPUTargetLowering::performFNegCombine(SDNode *N,
unsigned Opposite = inverseMinMax(Opc);
SDValue Res = DAG.getNode(Opposite, SL, VT, NegLHS, NegRHS, N0->getFlags());
if (Res.getOpcode() != Opposite)
return SDValue(); // Op got folded away.
if (!N0.hasOneUse())
DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
return Res;
@ -3776,6 +3784,8 @@ SDValue AMDGPUTargetLowering::performFNegCombine(SDNode *N,
Ops[I] = DAG.getNode(ISD::FNEG, SL, VT, N0->getOperand(I), N0->getFlags());
SDValue Res = DAG.getNode(AMDGPUISD::FMED3, SL, VT, Ops, N0->getFlags());
if (Res.getOpcode() != AMDGPUISD::FMED3)
return SDValue(); // Op got folded away.
if (!N0.hasOneUse())
DAG.ReplaceAllUsesWith(N0, DAG.getNode(ISD::FNEG, SL, VT, Res));
return Res;

22
llvm/test/CodeGen/AMDGPU/fneg-combines.ll
View File

@ -214,6 +214,28 @@ define amdgpu_kernel void @v_fneg_add_multi_use_fneg_x_f32(float addrspace(1)* %
ret void
}
; This one asserted with -enable-no-signed-zeros-fp-math
; GCN-LABEL: {{^}}fneg_fadd_0:
; GCN-SAFE-DAG: v_mad_f32 [[A:v[0-9]+]],
; GCN-SAFE-DAG: v_xor_b32_e32 [[B:v[0-9]+]], 0x80000000
; GCN-SAFE-DAG: v_cmp_ngt_f32_e32 {{.*}}, [[A]]
; GCN-NSZ-DAG: v_mac_f32_e32 [[C:v[0-9]+]],
; GCN-NSZ-DAG: v_cmp_nlt_f32_e64 {{.*}}, -[[C]]
define amdgpu_ps float @fneg_fadd_0(float inreg %tmp2, float inreg %tmp6, <4 x i32> %arg) local_unnamed_addr #0 {
.entry:
%tmp7 = fdiv float 1.000000e+00, %tmp6
%tmp8 = fmul float 0.000000e+00, %tmp7
%tmp9 = fmul reassoc nnan arcp contract float 0.000000e+00, %tmp8
%.i188 = fadd float %tmp9, 0.000000e+00
%tmp10 = fcmp uge float %.i188, %tmp2
%tmp11 = fsub float -0.000000e+00, %.i188
%.i092 = select i1 %tmp10, float %tmp2, float %tmp11
%tmp12 = fcmp ule float %.i092, 0.000000e+00
%.i198 = select i1 %tmp12, float 0.000000e+00, float 0x7FF8000000000000
ret float %.i198
}
; --------------------------------------------------------------------------------
; fmul tests
; --------------------------------------------------------------------------------