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[SLP][REVEC] Make GetMinMaxCost support FixedVectorType when REVEC is enabled. #114946

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merged 3 commits into from
Nov 7, 2024
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[SLP][REVEC] Make GetMinMaxCost support FixedVectorType when REVEC is enabled. #114946

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bf94802
[SLP][REVEC] Pre-commit test.
HanKuanChen Oct 31, 2024
46f323d
[SLP][REVEC] Remove assert because canConvertToMinOrMaxIntrinsic can
HanKuanChen Nov 5, 2024
9f4c52d
[SLP][REVEC] Make GetMinMaxCost support FixedVectorType when REVEC is
HanKuanChen Nov 6, 2024
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3 changes: 2 additions & 1 deletion llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10777,7 +10777,8 @@ BoUpSLP::getEntryCost(const TreeEntry *E, ArrayRef<Value *> VectorizedVals,
// If the selects are the only uses of the compares, they will be
// dead and we can adjust the cost by removing their cost.
if (VI && SelectOnly) {
assert(!Ty->isVectorTy() && "Expected only for scalar type.");
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Shall it be something like

assert((SLPReVec || !Ty->isVectorTy()) && "Expected only for scalar type.");

?

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I think the reason we use assert here is we don't want GetMinMaxCost accidentally remove the cost of CmpInst when the cost of vectorized code is estimated.

  case TreeEntry::MinMax: {
    auto GetScalarCost = [&](unsigned Idx) {
      return GetMinMaxCost(OrigScalarTy);
    };
    auto GetVectorCost = [&](InstructionCost CommonCost) {
      InstructionCost VecCost = GetMinMaxCost(VecTy);
      return VecCost + CommonCost;
    };
    return GetCostDiff(GetScalarCost, GetVectorCost);
  }

But GetVectorCost does not pass VI to GetMinMaxCost, so the assert will never be triggered.
Add SLPReVec here is weird because they mean different thing. It will make GetVectorCost accidentally minus the cost of CmpInst when REVEC is enabled. But it violates the original purpose of the assert.

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Then you need to adjust the cost estimation here by changing the condition type. Also, this assertion guarantees, that it is not called for vector cost

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Add SLPReVec is better.

assert((!Ty->isVectorTy() || SLPReVec) &&
"Expected only for scalar type.");
auto *CI = cast<CmpInst>(VI->getOperand(0));
IntrinsicCost -= TTI->getCmpSelInstrCost(
CI->getOpcode(), Ty, Builder.getInt1Ty(), CI->getPredicate(),
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40 changes: 40 additions & 0 deletions llvm/test/Transforms/SLPVectorizer/RISCV/revec.ll
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Expand Up @@ -94,3 +94,43 @@ entry:
%23 = fcmp ogt <8 x float> zeroinitializer, %19
ret void
}

define void @test3(float %0) {
; CHECK-LABEL: @test3(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_BODY_LR_PH:%.*]]
; CHECK: for.body.lr.ph:
; CHECK-NEXT: [[TMP1:%.*]] = call <4 x float> @llvm.vector.insert.v4f32.v2f32(<4 x float> poison, <2 x float> zeroinitializer, i64 0)
; CHECK-NEXT: [[TMP2:%.*]] = call <4 x float> @llvm.vector.insert.v4f32.v2f32(<4 x float> [[TMP1]], <2 x float> zeroinitializer, i64 2)
; CHECK-NEXT: br i1 false, label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY:%.*]]
; CHECK: for.cond.cleanup:
; CHECK-NEXT: [[TMP3:%.*]] = phi <4 x float> [ [[TMP2]], [[FOR_BODY_LR_PH]] ], [ [[TMP10:%.*]], [[FOR_BODY]] ]
; CHECK-NEXT: ret void
; CHECK: for.body:
; CHECK-NEXT: [[TMP4:%.*]] = load <2 x float>, ptr null, align 4
; CHECK-NEXT: [[TMP5:%.*]] = fcmp olt <2 x float> zeroinitializer, [[TMP4]]
; CHECK-NEXT: [[TMP6:%.*]] = call <4 x i1> @llvm.vector.insert.v4i1.v2i1(<4 x i1> poison, <2 x i1> <i1 true, i1 true>, i64 0)
; CHECK-NEXT: [[TMP7:%.*]] = call <4 x i1> @llvm.vector.insert.v4i1.v2i1(<4 x i1> [[TMP6]], <2 x i1> [[TMP5]], i64 2)
; CHECK-NEXT: [[TMP8:%.*]] = call <4 x float> @llvm.vector.insert.v4f32.v2f32(<4 x float> poison, <2 x float> [[TMP4]], i64 0)
; CHECK-NEXT: [[TMP9:%.*]] = shufflevector <4 x float> [[TMP8]], <4 x float> poison, <4 x i32> <i32 0, i32 1, i32 0, i32 1>
; CHECK-NEXT: [[TMP10]] = select <4 x i1> [[TMP7]], <4 x float> [[TMP9]], <4 x float> [[TMP2]]
; CHECK-NEXT: br label [[FOR_COND_CLEANUP]]
;
entry:
br label %for.body.lr.ph

for.body.lr.ph:
br i1 false, label %for.cond.cleanup, label %for.body

for.cond.cleanup: ; preds = %for.body, %for.body.lr.ph
%1 = phi <2 x float> [ zeroinitializer, %for.body.lr.ph ], [ %5, %for.body ]
%2 = phi <2 x float> [ zeroinitializer, %for.body.lr.ph ], [ %6, %for.body ]
ret void

for.body:
%3 = load <2 x float>, ptr null, align 4
%4 = fcmp olt <2 x float> zeroinitializer, %3
%5 = select <2 x i1> <i1 true, i1 true>, <2 x float> %3, <2 x float> zeroinitializer
%6 = select <2 x i1> %4, <2 x float> %3, <2 x float> zeroinitializer
br label %for.cond.cleanup
}
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