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[AMDGPU] Support bfloat comparison for ballot intrinsic (#165495) #479

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[AMDGPU] Support bfloat comparison for ballot intrinsic (#165495) #479

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ebda353
[AMDGPU] Support bfloat comparison for ballot intrinsic (#165495)
changpeng Oct 30, 2025
219cce9
[AMDGPU] Support bfloat comparison for ballot intrinsic (#165495)
changpeng Nov 4, 2025
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10 changes: 8 additions & 2 deletions llvm/lib/Target/AMDGPU/SIISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6430,9 +6430,15 @@ static SDValue lowerBALLOTIntrinsic(const SITargetLowering &TLI, SDNode *N,
SDLoc SL(N);

if (Src.getOpcode() == ISD::SETCC) {
SDValue Op0 = Src.getOperand(0);
SDValue Op1 = Src.getOperand(1);
// Need to expand bfloat to float for comparison (setcc).
if (Op0.getValueType() == MVT::bf16) {
Op0 = DAG.getNode(ISD::FP_EXTEND, SL, MVT::f32, Op0);
Op1 = DAG.getNode(ISD::FP_EXTEND, SL, MVT::f32, Op1);
}
// (ballot (ISD::SETCC ...)) -> (AMDGPUISD::SETCC ...)
return DAG.getNode(AMDGPUISD::SETCC, SL, VT, Src.getOperand(0),
Src.getOperand(1), Src.getOperand(2));
return DAG.getNode(AMDGPUISD::SETCC, SL, VT, Op0, Op1, Src.getOperand(2));
}
if (const ConstantSDNode *Arg = dyn_cast<ConstantSDNode>(Src)) {
// (ballot 0) -> 0
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12 changes: 12 additions & 0 deletions llvm/test/CodeGen/AMDGPU/llvm.amdgcn.ballot.i32.ll
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Expand Up @@ -591,3 +591,15 @@ exit:
store i32 %ballot, ptr addrspace(1) %out
ret void
}

define amdgpu_cs i32 @compare_bfloats(bfloat %x, bfloat %y) {
; CHECK-LABEL: compare_bfloats:
; CHECK: ; %bb.0:
; CHECK-NEXT: v_lshlrev_b32_e32 v1, 16, v1
; CHECK-NEXT: v_lshlrev_b32_e32 v0, 16, v0
; CHECK-NEXT: v_cmp_gt_f32_e64 s0, v0, v1
; CHECK-NEXT: ; return to shader part epilog
%cmp = fcmp ogt bfloat %x, %y
%ballot = call i32 @llvm.amdgcn.ballot.i32(i1 %cmp)
ret i32 %ballot
}
12 changes: 12 additions & 0 deletions llvm/test/CodeGen/AMDGPU/llvm.amdgcn.ballot.i64.ll
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Expand Up @@ -557,3 +557,15 @@ exit:
store i64 %ballot, ptr addrspace(1) %out
ret void
}

define amdgpu_cs i64 @compare_bfloats(bfloat %x, bfloat %y) {
; CHECK-LABEL: compare_bfloats:
; CHECK: ; %bb.0:
; CHECK-NEXT: v_lshlrev_b32_e32 v1, 16, v1
; CHECK-NEXT: v_lshlrev_b32_e32 v0, 16, v0
; CHECK-NEXT: v_cmp_gt_f32_e64 s[0:1], v0, v1
; CHECK-NEXT: ; return to shader part epilog
%cmp = fcmp ogt bfloat %x, %y
%ballot = call i64 @llvm.amdgcn.ballot.i64(i1 %cmp)
ret i64 %ballot
}