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[VPlan] Ignore incoming values with constant false mask. #89384

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Merged
merged 5 commits into from
Apr 23, 2024
Merged

[VPlan] Ignore incoming values with constant false mask. #89384

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fe47c38
[VPlan] Ignore incoming values with constant false mask.
fhahn Apr 19, 2024
97fc5c9
Merge remote-tracking branch 'origin/main' into vplan-simplify-blend-…
fhahn Apr 22, 2024
d66acc1
!fixup address comments, thanks!
fhahn Apr 22, 2024
d799e16
Merge remote-tracking branch 'origin/main' into vplan-simplify-blend-…
fhahn Apr 23, 2024
3aeb6a4
!fixup add comment for bitwidth arg
fhahn Apr 23, 2024
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17 changes: 12 additions & 5 deletions llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h
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Original file line number Diff line number Diff line change
Expand Up @@ -51,8 +51,9 @@ template <typename Class> struct bind_ty {
};

/// Match a specified integer value or vector of all elements of that
/// value.
struct specific_intval {
/// value. \p BitWidth optionally specifies the bitwidth the matched constant
/// must have. If it is 0, the matched constant can have any bitwidth.
template <unsigned BitWidth = 0> struct specific_intval {
APInt Val;

specific_intval(APInt V) : Val(std::move(V)) {}
Expand All @@ -66,15 +67,21 @@ struct specific_intval {
if (const auto *C = dyn_cast<Constant>(V))
CI = dyn_cast_or_null<ConstantInt>(
C->getSplatValue(/*AllowPoison=*/false));
if (!CI)
return false;

return CI && APInt::isSameValue(CI->getValue(), Val);
assert((BitWidth == 0 || CI->getBitWidth() == BitWidth) &&
"Trying the match constant with unexpected bitwidth.");
return APInt::isSameValue(CI->getValue(), Val);
}
};

inline specific_intval m_SpecificInt(uint64_t V) {
return specific_intval(APInt(64, V));
inline specific_intval<0> m_SpecificInt(uint64_t V) {
return specific_intval<0>(APInt(64, V));
}

inline specific_intval<1> m_False() { return specific_intval<1>(APInt(64, 0)); }
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Better assert the bitwidth is 1 when one tries to match False or True, rather than mismatch?

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Added an assert before checking APInt::isSameValue(CI->getValue(), Val), thanks!


/// Matching combinators
template <typename LTy, typename RTy> struct match_combine_or {
LTy L;
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5 changes: 3 additions & 2 deletions llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
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Expand Up @@ -884,18 +884,19 @@ void VPlanTransforms::clearReductionWrapFlags(VPlan &Plan) {

/// Try to simplify recipe \p R.
static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
using namespace llvm::VPlanPatternMatch;
// Try to remove redundant blend recipes.
if (auto *Blend = dyn_cast<VPBlendRecipe>(&R)) {
VPValue *Inc0 = Blend->getIncomingValue(0);
for (unsigned I = 1; I != Blend->getNumIncomingValues(); ++I)
if (Inc0 != Blend->getIncomingValue(I))
if (Inc0 != Blend->getIncomingValue(I) &&
!match(Blend->getMask(I), m_False()))
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This is fine, but could be more general: first filter all operands having false masks by replacing the original blend with a simpler blend, then apply the existing check if all operands are the same? May deserve additional tests.

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(Ah, mentioned in the commit message as follow-up, very well.)

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Will do separately, thanks!

return;
Blend->replaceAllUsesWith(Inc0);
Blend->eraseFromParent();
return;
}

using namespace llvm::VPlanPatternMatch;
VPValue *A;
if (match(&R, m_Trunc(m_ZExtOrSExt(m_VPValue(A))))) {
VPValue *Trunc = R.getVPSingleValue();
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6 changes: 1 addition & 5 deletions llvm/test/Transforms/LoopVectorize/unused-blend-mask-for-first-operand.ll
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Expand Up @@ -10,17 +10,13 @@ define void @test_not_first_lane_only_constant(ptr %A, ptr noalias %B) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
; CHECK: vector.ph:
; CHECK-NEXT: [[BROADCAST_SPLATINSERT3:%.*]] = insertelement <4 x ptr> poison, ptr [[B]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT4:%.*]] = shufflevector <4 x ptr> [[BROADCAST_SPLATINSERT3]], <4 x ptr> poison, <4 x i32> zeroinitializer
; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
; CHECK-NEXT: [[OFFSET_IDX:%.*]] = trunc i32 [[INDEX]] to i16
; CHECK-NEXT: [[TMP0:%.*]] = add i16 [[OFFSET_IDX]], 0
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i16, ptr [[A]], i16 [[TMP0]]
; CHECK-NEXT: [[PREDPHI:%.*]] = select <4 x i1> zeroinitializer, <4 x ptr> poison, <4 x ptr> [[BROADCAST_SPLAT4]]
; CHECK-NEXT: [[TMP12:%.*]] = extractelement <4 x ptr> [[PREDPHI]], i32 0
; CHECK-NEXT: [[TMP13:%.*]] = load i16, ptr [[TMP12]], align 2
; CHECK-NEXT: [[TMP13:%.*]] = load i16, ptr %B, align 2
; CHECK-NEXT: [[BROADCAST_SPLATINSERT5:%.*]] = insertelement <4 x i16> poison, i16 [[TMP13]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT6:%.*]] = shufflevector <4 x i16> [[BROADCAST_SPLATINSERT5]], <4 x i16> poison, <4 x i32> zeroinitializer
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i16, ptr [[TMP1]], i32 0
Expand Down