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[LV] Fix FindLastIV reduction for epilogue vectorization. #120395

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Merged
merged 7 commits into from
Jan 13, 2025
Merged

[LV] Fix FindLastIV reduction for epilogue vectorization. #120395

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840b295
[LV] Fix FindLastIV reduction for epilogue vectorization.
Mel-Chen Dec 18, 2024
98ab179
Revert "[LV] Fix FindLastIV reduction for epilogue vectorization."
Mel-Chen Dec 20, 2024
b3b436b
Revert "Revert "[LV] Fix FindLastIV reduction for epilogue vectorizat…
Mel-Chen Jan 9, 2025
1cf21f0
Revert "[LV] Fix FindLastIV reduction for epilogue vectorization."
Mel-Chen Jan 9, 2025
c6cf63f
Adjust resume value of FindLastIV
Mel-Chen Jan 10, 2025
3e5d819
Update llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
Mel-Chen Jan 13, 2025
ca464d0
Format
Mel-Chen Jan 13, 2025
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27 changes: 27 additions & 0 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7687,6 +7687,20 @@ static void fixReductionScalarResumeWhenVectorizingEpilog(
"AnyOf expected to start by comparing main resume value to original "
"start value");
MainResumeValue = Cmp->getOperand(0);
} else if (RecurrenceDescriptor::isFindLastIVRecurrenceKind(
RdxDesc.getRecurrenceKind())) {
using namespace llvm::PatternMatch;
Value *Cmp, *OrigResumeV;
bool IsExpectedPattern =
match(MainResumeValue, m_Select(m_OneUse(m_Value(Cmp)),
m_Specific(RdxDesc.getSentinelValue()),
m_Value(OrigResumeV))) &&
match(Cmp,
m_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(OrigResumeV),
m_Specific(RdxDesc.getRecurrenceStartValue())));
assert(IsExpectedPattern && "Unexpected reduction resume pattern");
(void)IsExpectedPattern;
MainResumeValue = OrigResumeV;
}
PHINode *MainResumePhi = cast<PHINode>(MainResumeValue);

Expand Down Expand Up @@ -10282,6 +10296,19 @@ preparePlanForEpilogueVectorLoop(VPlan &Plan, Loop *L,
cast<Instruction>(ResumeV)->getParent()->getFirstNonPHI());
ResumeV =
Builder.CreateICmpNE(ResumeV, RdxDesc.getRecurrenceStartValue());
} else if (RecurrenceDescriptor::isFindLastIVRecurrenceKind(RK)) {
// VPReductionPHIRecipe for FindLastIV reductions requires an adjustment
// to the resume value. The resume value is adjusted to the sentinel
// value when the final value from the main vector loop equals the start
// value. This ensures correctness when the start value might not be
// less than the minimum value of a monotonically increasing induction
// variable.
IRBuilder<> Builder(
cast<Instruction>(ResumeV)->getParent()->getFirstNonPHI());
Value *Cmp =
Builder.CreateICmpEQ(ResumeV, RdxDesc.getRecurrenceStartValue());
ResumeV =
Builder.CreateSelect(Cmp, RdxDesc.getSentinelValue(), ResumeV);
}
} else {
// Retrieve the induction resume values for wide inductions from
Expand Down
8 changes: 6 additions & 2 deletions llvm/test/Transforms/LoopVectorize/epilog-iv-select-cmp.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,9 @@ define i64 @select_icmp_const(ptr %a, i64 %n) {
; CHECK-NEXT: br i1 [[MIN_EPILOG_ITERS_CHECK]], label %[[VEC_EPILOG_SCALAR_PH]], label %[[VEC_EPILOG_PH]]
; CHECK: [[VEC_EPILOG_PH]]:
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ [[N_VEC]], %[[VEC_EPILOG_ITER_CHECK]] ], [ 0, %[[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
; CHECK-NEXT: [[BC_MERGE_RDX:%.*]] = phi i64 [ [[RDX_SELECT]], %[[VEC_EPILOG_ITER_CHECK]] ], [ 3, %[[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
; CHECK-NEXT: [[BC_MERGE_RDX1:%.*]] = phi i64 [ [[RDX_SELECT]], %[[VEC_EPILOG_ITER_CHECK]] ], [ 3, %[[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
; CHECK-NEXT: [[TMP14:%.*]] = icmp eq i64 [[BC_MERGE_RDX1]], 3
; CHECK-NEXT: [[BC_MERGE_RDX:%.*]] = select i1 [[TMP14]], i64 -9223372036854775808, i64 [[BC_MERGE_RDX1]]
; CHECK-NEXT: [[N_MOD_VF2:%.*]] = urem i64 [[N]], 4
; CHECK-NEXT: [[N_VEC3:%.*]] = sub i64 [[N]], [[N_MOD_VF2]]
; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <4 x i64> poison, i64 [[BC_RESUME_VAL]], i64 0
Expand Down Expand Up @@ -144,7 +146,9 @@ define i64 @select_fcmp_const_fast(ptr %a, i64 %n) {
; CHECK-NEXT: br i1 [[MIN_EPILOG_ITERS_CHECK]], label %[[VEC_EPILOG_SCALAR_PH]], label %[[VEC_EPILOG_PH]]
; CHECK: [[VEC_EPILOG_PH]]:
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ [[N_VEC]], %[[VEC_EPILOG_ITER_CHECK]] ], [ 0, %[[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
; CHECK-NEXT: [[BC_MERGE_RDX:%.*]] = phi i64 [ [[RDX_SELECT]], %[[VEC_EPILOG_ITER_CHECK]] ], [ 2, %[[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
; CHECK-NEXT: [[BC_MERGE_RDX1:%.*]] = phi i64 [ [[RDX_SELECT]], %[[VEC_EPILOG_ITER_CHECK]] ], [ 2, %[[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
; CHECK-NEXT: [[TMP14:%.*]] = icmp eq i64 [[BC_MERGE_RDX1]], 2
; CHECK-NEXT: [[BC_MERGE_RDX:%.*]] = select i1 [[TMP14]], i64 -9223372036854775808, i64 [[BC_MERGE_RDX1]]
; CHECK-NEXT: [[N_MOD_VF2:%.*]] = urem i64 [[N]], 4
; CHECK-NEXT: [[N_VEC3:%.*]] = sub i64 [[N]], [[N_MOD_VF2]]
; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <4 x i64> poison, i64 [[BC_RESUME_VAL]], i64 0
Expand Down
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