Successfully identified regression in *llvm* in CI configuration
tcwg_bmk_llvm_tx1/llvm-release-aarch64-spec2k6-O3. So far, this commit has
regressed CI configurations:
- tcwg_bmk_llvm_tx1/llvm-release-aarch64-spec2k6-O3
Culprit:
<cut>
commit 6998f8ae2d14e096aff33968f226587b5c1a193a
Author: David Sherwood <david.sherw...@arm.com>
Date: Wed Mar 10 08:34:19 2021 +0000
[LoopVectorize] Simplify scalar cost calculation in getInstructionCost
This patch simplifies the calculation of certain costs in
getInstructionCost when isScalarAfterVectorization() returns a true value.
There are a few places where we multiply a cost by a number N, i.e.
unsigned N = isScalarAfterVectorization(I, VF) ? VF.getKnownMinValue() :
1;
return N * TTI.getArithmeticInstrCost(...
After some investigation it seems that there are only these cases that occur
in practice:
1. VF is a scalar, in which case N = 1.
2. VF is a vector. We can only get here if: a) the instruction is a
GEP/bitcast/PHI with scalar uses, or b) this is an update to an induction
variable that remains scalar.
I have changed the code so that N is assumed to always be 1. For GEPs
the cost is always 0, since this is calculated later on as part of the
load/store cost. PHI nodes are costed separately and were never previously
multiplied by VF. For all other cases I have added an assert that none of
the users needs scalarising, which didn't fire in any unit tests.
Only one test required fixing and I believe the original cost for the scalar
add instruction to have been wrong, since only one copy remains after
vectorisation.
I have also added a new test for the case when a pointer PHI feeds directly
into a store that will be scalarised as we were previously never testing it.
Differential Revision: https://reviews.llvm.org/D99718
</cut>
Results regressed to (for first_bad == 6998f8ae2d14e096aff33968f226587b5c1a193a)
# reset_artifacts:
-10
# build_abe binutils:
-9
# build_abe stage1 -- --set gcc_override_configure=--disable-libsanitizer:
-8
# build_abe linux:
-7
# build_abe glibc:
-6
# build_abe stage2 -- --set gcc_override_configure=--disable-libsanitizer:
-5
# build_llvm true:
-3
# true:
0
# benchmark -- -O3
artifacts/build-6998f8ae2d14e096aff33968f226587b5c1a193a/results_id:
1
# 462.libquantum,libquantum_base.default regressed by 114
# 462.libquantum,[.] quantum_toffoli regressed by 123
# 462.libquantum,[.] quantum_cnot regressed by 115
from (for last_good == c835630c25a4f9925517949579f66a43b113fbc9)
# reset_artifacts:
-10
# build_abe binutils:
-9
# build_abe stage1 -- --set gcc_override_configure=--disable-libsanitizer:
-8
# build_abe linux:
-7
# build_abe glibc:
-6
# build_abe stage2 -- --set gcc_override_configure=--disable-libsanitizer:
-5
# build_llvm true:
-3
# true:
0
# benchmark -- -O3
artifacts/build-c835630c25a4f9925517949579f66a43b113fbc9/results_id:
1
Artifacts of last_good build:
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/artifact/artifacts/build-c835630c25a4f9925517949579f66a43b113fbc9/
Results ID of last_good:
tx1_64/tcwg_bmk_llvm_tx1/bisect-llvm-release-aarch64-spec2k6-O3/3744
Artifacts of first_bad build:
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/artifact/artifacts/build-6998f8ae2d14e096aff33968f226587b5c1a193a/
Results ID of first_bad:
tx1_64/tcwg_bmk_llvm_tx1/bisect-llvm-release-aarch64-spec2k6-O3/3755
Build top page/logs:
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/
Configuration details:
Reproduce builds:
<cut>
mkdir investigate-llvm-6998f8ae2d14e096aff33968f226587b5c1a193a
cd investigate-llvm-6998f8ae2d14e096aff33968f226587b5c1a193a
git clone https://git.linaro.org/toolchain/jenkins-scripts
mkdir -p artifacts/manifests
curl -o artifacts/manifests/build-baseline.sh
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/artifact/artifacts/manifests/build-baseline.sh
--fail
curl -o artifacts/manifests/build-parameters.sh
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/artifact/artifacts/manifests/build-parameters.sh
--fail
curl -o artifacts/test.sh
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/artifact/artifacts/test.sh
--fail
chmod +x artifacts/test.sh
# Reproduce the baseline build (build all pre-requisites)
./jenkins-scripts/tcwg_bmk-build.sh @@ artifacts/manifests/build-baseline.sh
# Save baseline build state (which is then restored in artifacts/test.sh)
mkdir -p ./bisect
rsync -a --del --delete-excluded --exclude /bisect/ --exclude /artifacts/
--exclude /llvm/ ./ ./bisect/baseline/
cd llvm
# Reproduce first_bad build
git checkout --detach 6998f8ae2d14e096aff33968f226587b5c1a193a
../artifacts/test.sh
# Reproduce last_good build
git checkout --detach c835630c25a4f9925517949579f66a43b113fbc9
../artifacts/test.sh
cd ..
</cut>
History of pending regressions and results:
https://git.linaro.org/toolchain/ci/base-artifacts.git/log/?h=linaro-local/ci/tcwg_bmk_llvm_tx1/llvm-release-aarch64-spec2k6-O3
Artifacts:
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/artifact/artifacts/
Build log:
https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tx1-llvm-release-aarch64-spec2k6-O3/7/consoleText
Full commit (up to 1000 lines):
<cut>
commit 6998f8ae2d14e096aff33968f226587b5c1a193a
Author: David Sherwood <david.sherw...@arm.com>
Date: Wed Mar 10 08:34:19 2021 +0000
[LoopVectorize] Simplify scalar cost calculation in getInstructionCost
This patch simplifies the calculation of certain costs in
getInstructionCost when isScalarAfterVectorization() returns a true value.
There are a few places where we multiply a cost by a number N, i.e.
unsigned N = isScalarAfterVectorization(I, VF) ? VF.getKnownMinValue() :
1;
return N * TTI.getArithmeticInstrCost(...
After some investigation it seems that there are only these cases that occur
in practice:
1. VF is a scalar, in which case N = 1.
2. VF is a vector. We can only get here if: a) the instruction is a
GEP/bitcast/PHI with scalar uses, or b) this is an update to an induction
variable that remains scalar.
I have changed the code so that N is assumed to always be 1. For GEPs
the cost is always 0, since this is calculated later on as part of the
load/store cost. PHI nodes are costed separately and were never previously
multiplied by VF. For all other cases I have added an assert that none of
the users needs scalarising, which didn't fire in any unit tests.
Only one test required fixing and I believe the original cost for the scalar
add instruction to have been wrong, since only one copy remains after
vectorisation.
I have also added a new test for the case when a pointer PHI feeds directly
into a store that will be scalarised as we were previously never testing it.
Differential Revision: https://reviews.llvm.org/D99718
---
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 73 +++++++++++++---------
.../AArch64/no_vector_instructions.ll | 2 +-
.../LoopVectorize/AArch64/predication_costs.ll | 35 +++++++++++
.../Transforms/LoopVectorize/scalarized-bitcast.ll | 40 ++++++++++++
4 files changed, 121 insertions(+), 29 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 2b413fc49505..f25af23c86c2 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7383,10 +7383,39 @@
LoopVectorizationCostModel::getInstructionCost(Instruction *I, ElementCount VF,
Type *RetTy = I->getType();
if (canTruncateToMinimalBitwidth(I, VF))
RetTy = IntegerType::get(RetTy->getContext(), MinBWs[I]);
- VectorTy = isScalarAfterVectorization(I, VF) ? RetTy : ToVectorTy(RetTy, VF);
auto SE = PSE.getSE();
TTI::TargetCostKind CostKind = TTI::TCK_RecipThroughput;
+ auto hasSingleCopyAfterVectorization = [this](Instruction *I,
+ ElementCount VF) -> bool {
+ if (VF.isScalar())
+ return true;
+
+ auto Scalarized = InstsToScalarize.find(VF);
+ assert(Scalarized != InstsToScalarize.end() &&
+ "VF not yet analyzed for scalarization profitability");
+ return !Scalarized->second.count(I) &&
+ llvm::all_of(I->users(), [&](User *U) {
+ auto *UI = cast<Instruction>(U);
+ return !Scalarized->second.count(UI);
+ });
+ };
+
+ if (isScalarAfterVectorization(I, VF)) {
+ // With the exception of GEPs and PHIs, after scalarization there should
+ // only be one copy of the instruction generated in the loop. This is
+ // because the VF is either 1, or any instructions that need scalarizing
+ // have already been dealt with by the the time we get here. As a result,
+ // it means we don't have to multiply the instruction cost by VF.
+ assert(I->getOpcode() == Instruction::GetElementPtr ||
+ I->getOpcode() == Instruction::PHI ||
+ (I->getOpcode() == Instruction::BitCast &&
+ I->getType()->isPointerTy()) ||
+ hasSingleCopyAfterVectorization(I, VF));
+ VectorTy = RetTy;
+ } else
+ VectorTy = ToVectorTy(RetTy, VF);
+
// TODO: We need to estimate the cost of intrinsic calls.
switch (I->getOpcode()) {
case Instruction::GetElementPtr:
@@ -7514,21 +7543,16 @@
LoopVectorizationCostModel::getInstructionCost(Instruction *I, ElementCount VF,
Op2VK = TargetTransformInfo::OK_UniformValue;
SmallVector<const Value *, 4> Operands(I->operand_values());
- unsigned N = isScalarAfterVectorization(I, VF) ? VF.getKnownMinValue() : 1;
- return N * TTI.getArithmeticInstrCost(
- I->getOpcode(), VectorTy, CostKind,
- TargetTransformInfo::OK_AnyValue,
- Op2VK, TargetTransformInfo::OP_None, Op2VP, Operands, I);
+ return TTI.getArithmeticInstrCost(
+ I->getOpcode(), VectorTy, CostKind, TargetTransformInfo::OK_AnyValue,
+ Op2VK, TargetTransformInfo::OP_None, Op2VP, Operands, I);
}
case Instruction::FNeg: {
assert(!VF.isScalable() && "VF is assumed to be non scalable.");
- unsigned N = isScalarAfterVectorization(I, VF) ? VF.getKnownMinValue() : 1;
- return N * TTI.getArithmeticInstrCost(
- I->getOpcode(), VectorTy, CostKind,
- TargetTransformInfo::OK_AnyValue,
- TargetTransformInfo::OK_AnyValue,
- TargetTransformInfo::OP_None, TargetTransformInfo::OP_None,
- I->getOperand(0), I);
+ return TTI.getArithmeticInstrCost(
+ I->getOpcode(), VectorTy, CostKind, TargetTransformInfo::OK_AnyValue,
+ TargetTransformInfo::OK_AnyValue, TargetTransformInfo::OP_None,
+ TargetTransformInfo::OP_None, I->getOperand(0), I);
}
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
@@ -7583,6 +7607,10 @@
LoopVectorizationCostModel::getInstructionCost(Instruction *I, ElementCount VF,
VectorTy = ToVectorTy(getMemInstValueType(I), Width);
return getMemoryInstructionCost(I, VF);
}
+ case Instruction::BitCast:
+ if (I->getType()->isPointerTy())
+ return 0;
+ LLVM_FALLTHROUGH;
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPToUI:
@@ -7593,8 +7621,7 @@
LoopVectorizationCostModel::getInstructionCost(Instruction *I, ElementCount VF,
case Instruction::SIToFP:
case Instruction::UIToFP:
case Instruction::Trunc:
- case Instruction::FPTrunc:
- case Instruction::BitCast: {
+ case Instruction::FPTrunc: {
// Computes the CastContextHint from a Load/Store instruction.
auto ComputeCCH = [&](Instruction *I) -> TTI::CastContextHint {
assert((isa<LoadInst>(I) || isa<StoreInst>(I)) &&
@@ -7672,14 +7699,7 @@
LoopVectorizationCostModel::getInstructionCost(Instruction *I, ElementCount VF,
}
}
- unsigned N;
- if (isScalarAfterVectorization(I, VF)) {
- assert(!VF.isScalable() && "VF is assumed to be non scalable");
- N = VF.getKnownMinValue();
- } else
- N = 1;
- return N *
- TTI.getCastInstrCost(Opcode, VectorTy, SrcVecTy, CCH, CostKind, I);
+ return TTI.getCastInstrCost(Opcode, VectorTy, SrcVecTy, CCH, CostKind, I);
}
case Instruction::Call: {
bool NeedToScalarize;
@@ -7694,11 +7714,8 @@
LoopVectorizationCostModel::getInstructionCost(Instruction *I, ElementCount VF,
case Instruction::ExtractValue:
return TTI.getInstructionCost(I, TTI::TCK_RecipThroughput);
default:
- // The cost of executing VF copies of the scalar instruction. This opcode
- // is unknown. Assume that it is the same as 'mul'.
- return VF.getKnownMinValue() * TTI.getArithmeticInstrCost(
- Instruction::Mul, VectorTy, CostKind) +
- getScalarizationOverhead(I, VF);
+ // This opcode is unknown. Assume that it is the same as 'mul'.
+ return TTI.getArithmeticInstrCost(Instruction::Mul, VectorTy, CostKind);
} // end of switch.
}
diff --git
a/llvm/test/Transforms/LoopVectorize/AArch64/no_vector_instructions.ll
b/llvm/test/Transforms/LoopVectorize/AArch64/no_vector_instructions.ll
index 247ea35ff5d0..3061998518ad 100644
--- a/llvm/test/Transforms/LoopVectorize/AArch64/no_vector_instructions.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/no_vector_instructions.ll
@@ -6,7 +6,7 @@ target triple = "aarch64--linux-gnu"
; CHECK-LABEL: all_scalar
; CHECK: LV: Found scalar instruction: %i.next = add nuw nsw i64 %i, 2
-; CHECK: LV: Found an estimated cost of 2 for VF 2 For instruction:
%i.next = add nuw nsw i64 %i, 2
+; CHECK: LV: Found an estimated cost of 1 for VF 2 For instruction:
%i.next = add nuw nsw i64 %i, 2
; CHECK: LV: Not considering vector loop of width 2 because it will not
generate any vector instructions
;
define void @all_scalar(i64* %a, i64 %n) {
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/predication_costs.ll
b/llvm/test/Transforms/LoopVectorize/AArch64/predication_costs.ll
index b0ebb4edf2ad..858b28ddd321 100644
--- a/llvm/test/Transforms/LoopVectorize/AArch64/predication_costs.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/predication_costs.ll
@@ -86,6 +86,41 @@ for.end:
ret void
}
+; CHECK-LABEL: predicated_store_phi
+;
+; Same as predicate_store except we use a pointer PHI to maintain the address
+;
+; CHECK: Found new scalar instruction: %addr = phi i32* [ %a, %entry ], [
%addr.next, %for.inc ]
+; CHECK: Found new scalar instruction: %addr.next = getelementptr inbounds
i32, i32* %addr, i64 1
+; CHECK: Scalarizing and predicating: store i32 %tmp2, i32* %addr, align 4
+; CHECK: Found an estimated cost of 0 for VF 2 For instruction: %addr = phi
i32* [ %a, %entry ], [ %addr.next, %for.inc ]
+; CHECK: Found an estimated cost of 3 for VF 2 For instruction: store i32
%tmp2, i32* %addr, align 4
+;
+define void @predicated_store_phi(i32* %a, i1 %c, i32 %x, i64 %n) {
+entry:
+ br label %for.body
+
+for.body:
+ %i = phi i64 [ 0, %entry ], [ %i.next, %for.inc ]
+ %addr = phi i32 * [ %a, %entry ], [ %addr.next, %for.inc ]
+ %tmp1 = load i32, i32* %addr, align 4
+ %tmp2 = add nsw i32 %tmp1, %x
+ br i1 %c, label %if.then, label %for.inc
+
+if.then:
+ store i32 %tmp2, i32* %addr, align 4
+ br label %for.inc
+
+for.inc:
+ %i.next = add nuw nsw i64 %i, 1
+ %cond = icmp slt i64 %i.next, %n
+ %addr.next = getelementptr inbounds i32, i32* %addr, i64 1
+ br i1 %cond, label %for.body, label %for.end
+
+for.end:
+ ret void
+}
+
; CHECK-LABEL: predicated_udiv_scalarized_operand
;
; This test checks that we correctly compute the cost of the predicated udiv
diff --git a/llvm/test/Transforms/LoopVectorize/scalarized-bitcast.ll
b/llvm/test/Transforms/LoopVectorize/scalarized-bitcast.ll
new file mode 100644
index 000000000000..0c97e6ac475e
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/scalarized-bitcast.ll
@@ -0,0 +1,40 @@
+; REQUIRES: asserts
+; RUN: opt -loop-vectorize -force-vector-width=2 -debug-only=loop-vectorize -S
-o - < %s 2>&1 | FileCheck %s
+
+%struct.foo = type { i32, i64 }
+
+; CHECK: LV: Found an estimated cost of 0 for VF 2 For instruction: %0 =
bitcast i64* %b to i32*
+
+; The bitcast below will be scalarized due to the predication in the loop.
Bitcasts
+; between pointer types should be treated as free, despite the scalarization.
+define void @foo(%struct.foo* noalias nocapture %in, i32* noalias nocapture
readnone %out, i64 %n) {
+entry:
+ br label %for.body
+
+for.body: ; preds = %entry, %if.end
+ %i.012 = phi i64 [ %inc, %if.end ], [ 0, %entry ]
+ %b = getelementptr inbounds %struct.foo, %struct.foo* %in, i64 %i.012, i32 1
+ %0 = bitcast i64* %b to i32*
+ %a = getelementptr inbounds %struct.foo, %struct.foo* %in, i64 %i.012, i32 0
+ %1 = load i32, i32* %a, align 8
+ %tobool.not = icmp eq i32 %1, 0
+ br i1 %tobool.not, label %if.end, label %land.lhs.true
+
+land.lhs.true: ; preds = %for.body
+ %2 = load i32, i32* %0, align 4
+ %cmp2 = icmp sgt i32 %2, 0
+ br i1 %cmp2, label %if.then, label %if.end
+
+if.then: ; preds = %land.lhs.true
+ %sub = add nsw i32 %2, -1
+ store i32 %sub, i32* %0, align 4
+ br label %if.end
+
+if.end: ; preds = %if.then,
%land.lhs.true, %for.body
+ %inc = add nuw nsw i64 %i.012, 1
+ %exitcond.not = icmp eq i64 %inc, %n
+ br i1 %exitcond.not, label %for.end, label %for.body
+
+for.end: ; preds = %if.end
+ ret void
+}
</cut>
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