[llvm] fd2f8d4 - [LoadStoreVectorizer] Postprocess and merge equivalence classes (#114501)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Dec 11 19:01:38 PST 2024
Author: Vyacheslav Klochkov
Date: 2024-12-11T19:01:35-08:00
New Revision: fd2f8d485df7742320317b14d49b9d808f70625c
URL: https://github.com/llvm/llvm-project/commit/fd2f8d485df7742320317b14d49b9d808f70625c
DIFF: https://github.com/llvm/llvm-project/commit/fd2f8d485df7742320317b14d49b9d808f70625c.diff
LOG: [LoadStoreVectorizer] Postprocess and merge equivalence classes (#114501)
This patch introduces a new method:
void Vectorizer::mergeEquivalenceClasses(EquivalenceClassMap &EQClasses)
const
The method is called at the end of
Vectorizer::collectEquivalenceClasses() and is needed to merge
equivalence classes that differ only by their underlying objects (UO1
and UO2), where UO1 is 1-level-indirection underlying base for UO2. This
situation arises due to the limited lookup depth used during the search
of underlying bases with llvm::getUnderlyingObject(ptr).
Using any fixed lookup depth can result into creation of multiple
equivalence classes that only differ by 1-level indirection bases.
The new approach merges equivalence classes if they have adjacent bases
(1-level indirection). If a series of equivalence classes form ladder
formed of 1-step/level indirections, they are all merged into a single
equivalence class. This provides more opportunities for the load-store
vectorizer to generate better vectors.
---------
Signed-off-by: Klochkov, Vyacheslav N <vyacheslav.n.klochkov at intel.com>
Added:
llvm/test/Transforms/LoadStoreVectorizer/X86/massive_indirection.ll
Modified:
llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp b/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
index 02ec1d5c259cd6..9f24181d5d1f6d 100644
--- a/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
@@ -324,6 +324,11 @@ class Vectorizer {
Instruction *ChainElem, Instruction *ChainBegin,
const DenseMap<Instruction *, APInt /*OffsetFromLeader*/> &ChainOffsets);
+ /// Merges the equivalence classes if they have underlying objects that
diff er
+ /// by one level of indirection (i.e., one is a getelementptr and the other is
+ /// the base pointer in that getelementptr).
+ void mergeEquivalenceClasses(EquivalenceClassMap &EQClasses) const;
+
/// Collects loads and stores grouped by "equivalence class", where:
/// - all elements in an eq class are a load or all are a store,
/// - they all load/store the same element size (it's OK to have e.g. i8 and
@@ -1305,6 +1310,123 @@ std::optional<APInt> Vectorizer::getConstantOffsetSelects(
return std::nullopt;
}
+void Vectorizer::mergeEquivalenceClasses(EquivalenceClassMap &EQClasses) const {
+ if (EQClasses.size() < 2) // There is nothing to merge.
+ return;
+
+ // The reduced key has all elements of the ECClassKey except the underlying
+ // object. Check that EqClassKey has 4 elements and define the reduced key.
+ static_assert(std::tuple_size_v<EqClassKey> == 4,
+ "EqClassKey has changed - EqClassReducedKey needs changes too");
+ using EqClassReducedKey =
+ std::tuple<std::tuple_element_t<1, EqClassKey> /* AddrSpace */,
+ std::tuple_element_t<2, EqClassKey> /* Element size */,
+ std::tuple_element_t<3, EqClassKey> /* IsLoad; */>;
+ using ECReducedKeyToUnderlyingObjectMap =
+ MapVector<EqClassReducedKey,
+ SmallPtrSet<std::tuple_element_t<0, EqClassKey>, 4>>;
+
+ // Form a map from the reduced key (without the underlying object) to the
+ // underlying objects: 1 reduced key to many underlying objects, to form
+ // groups of potentially merge-able equivalence classes.
+ ECReducedKeyToUnderlyingObjectMap RedKeyToUOMap;
+ bool FoundPotentiallyOptimizableEC = false;
+ for (const auto &EC : EQClasses) {
+ const auto &Key = EC.first;
+ EqClassReducedKey RedKey{std::get<1>(Key), std::get<2>(Key),
+ std::get<3>(Key)};
+ RedKeyToUOMap[RedKey].insert(std::get<0>(Key));
+ if (RedKeyToUOMap[RedKey].size() > 1)
+ FoundPotentiallyOptimizableEC = true;
+ }
+ if (!FoundPotentiallyOptimizableEC)
+ return;
+
+ LLVM_DEBUG({
+ dbgs() << "LSV: mergeEquivalenceClasses: before merging:\n";
+ for (const auto &EC : EQClasses) {
+ dbgs() << " Key: ([" << std::get<0>(EC.first)
+ << "]: " << *std::get<0>(EC.first) << ", " << std::get<1>(EC.first)
+ << ", " << std::get<2>(EC.first) << ", "
+ << static_cast<int>(std::get<3>(EC.first)) << ")\n";
+ for (const auto &Inst : EC.second)
+ dbgs() << "\tInst: " << *Inst << '\n';
+ }
+ });
+ LLVM_DEBUG({
+ dbgs() << "LSV: mergeEquivalenceClasses: RedKeyToUOMap:\n";
+ for (const auto &RedKeyToUO : RedKeyToUOMap) {
+ dbgs() << " Reduced key: (" << std::get<0>(RedKeyToUO.first) << ", "
+ << std::get<1>(RedKeyToUO.first) << ", "
+ << static_cast<int>(std::get<2>(RedKeyToUO.first)) << ") --> "
+ << RedKeyToUO.second.size() << " underlying objects:\n";
+ for (auto UObject : RedKeyToUO.second)
+ dbgs() << " [" << UObject << "]: " << *UObject << '\n';
+ }
+ });
+
+ using UObjectToUObjectMap = DenseMap<const Value *, const Value *>;
+
+ // Compute the ultimate targets for a set of underlying objects.
+ auto GetUltimateTargets =
+ [](SmallPtrSetImpl<const Value *> &UObjects) -> UObjectToUObjectMap {
+ UObjectToUObjectMap IndirectionMap;
+ for (const auto *UObject : UObjects) {
+ const unsigned MaxLookupDepth = 1; // look for 1-level indirections only
+ const auto *UltimateTarget = getUnderlyingObject(UObject, MaxLookupDepth);
+ if (UltimateTarget != UObject)
+ IndirectionMap[UObject] = UltimateTarget;
+ }
+ UObjectToUObjectMap UltimateTargetsMap;
+ for (const auto *UObject : UObjects) {
+ auto Target = UObject;
+ auto It = IndirectionMap.find(Target);
+ for (; It != IndirectionMap.end(); It = IndirectionMap.find(Target))
+ Target = It->second;
+ UltimateTargetsMap[UObject] = Target;
+ }
+ return UltimateTargetsMap;
+ };
+
+ // For each item in RedKeyToUOMap, if it has more than one underlying object,
+ // try to merge the equivalence classes.
+ for (auto &[RedKey, UObjects] : RedKeyToUOMap) {
+ if (UObjects.size() < 2)
+ continue;
+ auto UTMap = GetUltimateTargets(UObjects);
+ for (const auto &[UObject, UltimateTarget] : UTMap) {
+ if (UObject == UltimateTarget)
+ continue;
+
+ EqClassKey KeyFrom{UObject, std::get<0>(RedKey), std::get<1>(RedKey),
+ std::get<2>(RedKey)};
+ EqClassKey KeyTo{UltimateTarget, std::get<0>(RedKey), std::get<1>(RedKey),
+ std::get<2>(RedKey)};
+ const auto &VecFrom = EQClasses[KeyFrom];
+ const auto &VecTo = EQClasses[KeyTo];
+ SmallVector<Instruction *, 8> MergedVec;
+ std::merge(VecFrom.begin(), VecFrom.end(), VecTo.begin(), VecTo.end(),
+ std::back_inserter(MergedVec),
+ [](Instruction *A, Instruction *B) {
+ return A && B && A->comesBefore(B);
+ });
+ EQClasses[KeyTo] = std::move(MergedVec);
+ EQClasses.erase(KeyFrom);
+ }
+ }
+ LLVM_DEBUG({
+ dbgs() << "LSV: mergeEquivalenceClasses: after merging:\n";
+ for (const auto &EC : EQClasses) {
+ dbgs() << " Key: ([" << std::get<0>(EC.first)
+ << "]: " << *std::get<0>(EC.first) << ", " << std::get<1>(EC.first)
+ << ", " << std::get<2>(EC.first) << ", "
+ << static_cast<int>(std::get<3>(EC.first)) << ")\n";
+ for (const auto &Inst : EC.second)
+ dbgs() << "\tInst: " << *Inst << '\n';
+ }
+ });
+}
+
EquivalenceClassMap
Vectorizer::collectEquivalenceClasses(BasicBlock::iterator Begin,
BasicBlock::iterator End) {
@@ -1377,6 +1499,7 @@ Vectorizer::collectEquivalenceClasses(BasicBlock::iterator Begin,
.emplace_back(&I);
}
+ mergeEquivalenceClasses(Ret);
return Ret;
}
diff --git a/llvm/test/Transforms/LoadStoreVectorizer/X86/massive_indirection.ll b/llvm/test/Transforms/LoadStoreVectorizer/X86/massive_indirection.ll
new file mode 100644
index 00000000000000..c4b0d2e311d9d7
--- /dev/null
+++ b/llvm/test/Transforms/LoadStoreVectorizer/X86/massive_indirection.ll
@@ -0,0 +1,142 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt %s -mtriple=x86_64-unknown-linux-gnu -passes=load-store-vectorizer -mcpu=skx -S -o - | FileCheck %s
+
+; This test verifies that the vectorizer can handle an extended sequence of
+; getelementptr instructions and generate longer vectors. With special handling,
+; some elements can still be vectorized even if they require looking up the
+; common underlying object deeper than 6 levels from the original pointer.
+
+; The test below is the simplified version of actual performance oriented
+; workload; the offsets in getelementptr instructions are similar or same for
+; the test simplicity.
+
+define void @v1_v2_v4_v1_to_v8_levels_6_7_8_8(i32 %arg0, ptr align 16 %arg1) {
+; CHECK-LABEL: define void @v1_v2_v4_v1_to_v8_levels_6_7_8_8(
+; CHECK-SAME: i32 [[ARG0:%.*]], ptr align 16 [[ARG1:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: [[LEVEL1:%.*]] = getelementptr i8, ptr [[ARG1]], i32 917504
+; CHECK-NEXT: [[LEVEL2:%.*]] = getelementptr i8, ptr [[LEVEL1]], i32 [[ARG0]]
+; CHECK-NEXT: [[LEVEL3:%.*]] = getelementptr i8, ptr [[LEVEL2]], i32 32768
+; CHECK-NEXT: [[LEVEL4:%.*]] = getelementptr i8, ptr [[LEVEL3]], i32 [[ARG0]]
+; CHECK-NEXT: [[LEVEL5:%.*]] = getelementptr i8, ptr [[LEVEL4]], i32 [[ARG0]]
+; CHECK-NEXT: [[A6:%.*]] = getelementptr i8, ptr [[LEVEL5]], i32 [[ARG0]]
+; CHECK-NEXT: store <8 x half> zeroinitializer, ptr [[A6]], align 16
+; CHECK-NEXT: ret void
+;
+
+ %level1 = getelementptr i8, ptr %arg1, i32 917504
+ %level2 = getelementptr i8, ptr %level1, i32 %arg0
+ %level3 = getelementptr i8, ptr %level2, i32 32768
+ %level4 = getelementptr i8, ptr %level3, i32 %arg0
+ %level5 = getelementptr i8, ptr %level4, i32 %arg0
+
+ %a6 = getelementptr i8, ptr %level5, i32 %arg0
+ %b7 = getelementptr i8, ptr %a6, i32 2
+ %c8 = getelementptr i8, ptr %b7, i32 8
+ %d8 = getelementptr i8, ptr %b7, i32 12
+
+ store half 0xH0000, ptr %a6, align 16
+ store <4 x half> zeroinitializer, ptr %b7, align 2
+ store <2 x half> zeroinitializer, ptr %c8, align 2
+ store half 0xH0000, ptr %d8, align 2
+ ret void
+}
+
+define void @v1x8_levels_6_7_8_9_10_11_12_13(i32 %arg0, ptr align 16 %arg1) {
+; CHECK-LABEL: define void @v1x8_levels_6_7_8_9_10_11_12_13(
+; CHECK-SAME: i32 [[ARG0:%.*]], ptr align 16 [[ARG1:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[LEVEL1:%.*]] = getelementptr i8, ptr [[ARG1]], i32 917504
+; CHECK-NEXT: [[LEVEL2:%.*]] = getelementptr i8, ptr [[LEVEL1]], i32 [[ARG0]]
+; CHECK-NEXT: [[LEVEL3:%.*]] = getelementptr i8, ptr [[LEVEL2]], i32 32768
+; CHECK-NEXT: [[LEVEL4:%.*]] = getelementptr i8, ptr [[LEVEL3]], i32 [[ARG0]]
+; CHECK-NEXT: [[LEVEL5:%.*]] = getelementptr i8, ptr [[LEVEL4]], i32 [[ARG0]]
+; CHECK-NEXT: [[A6:%.*]] = getelementptr i8, ptr [[LEVEL5]], i32 [[ARG0]]
+; CHECK-NEXT: store <8 x half> zeroinitializer, ptr [[A6]], align 16
+; CHECK-NEXT: ret void
+;
+
+ %level1 = getelementptr i8, ptr %arg1, i32 917504
+ %level2 = getelementptr i8, ptr %level1, i32 %arg0
+ %level3 = getelementptr i8, ptr %level2, i32 32768
+ %level4 = getelementptr i8, ptr %level3, i32 %arg0
+ %level5 = getelementptr i8, ptr %level4, i32 %arg0
+
+ %a6 = getelementptr i8, ptr %level5, i32 %arg0
+ %b7 = getelementptr i8, ptr %a6, i32 2
+ %c8 = getelementptr i8, ptr %b7, i32 2
+ %d9 = getelementptr i8, ptr %c8, i32 2
+ %e10 = getelementptr i8, ptr %d9, i32 2
+ %f11 = getelementptr i8, ptr %e10, i32 2
+ %g12 = getelementptr i8, ptr %f11, i32 2
+ %h13 = getelementptr i8, ptr %g12, i32 2
+
+ store half 0xH0000, ptr %a6, align 16
+ store half 0xH0000, ptr %b7, align 2
+ store half 0xH0000, ptr %c8, align 2
+ store half 0xH0000, ptr %d9, align 2
+ store half 0xH0000, ptr %e10, align 8
+ store half 0xH0000, ptr %f11, align 2
+ store half 0xH0000, ptr %g12, align 2
+ store half 0xH0000, ptr %h13, align 2
+ ret void
+}
+
+define void @v1_4_4_4_2_1_to_v8_8_levels_6_7(i32 %arg0, ptr addrspace(3) align 16 %arg1_ptr, i32 %arg2, i32 %arg3, i32 %arg4, i32 %arg5, half %arg6_half, half %arg7_half, <2 x half> %arg8_2xhalf) {
+; CHECK-LABEL: define void @v1_4_4_4_2_1_to_v8_8_levels_6_7(
+; CHECK-SAME: i32 [[ARG0:%.*]], ptr addrspace(3) align 16 [[ARG1_PTR:%.*]], i32 [[ARG2:%.*]], i32 [[ARG3:%.*]], i32 [[ARG4:%.*]], i32 [[ARG5:%.*]], half [[ARG6_HALF:%.*]], half [[ARG7_HALF:%.*]], <2 x half> [[ARG8_2XHALF:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds i8, ptr addrspace(3) [[ARG1_PTR]], i32 458752
+; CHECK-NEXT: br [[DOTPREHEADER11_PREHEADER:label %.*]]
+; CHECK: [[_PREHEADER11_PREHEADER:.*:]]
+; CHECK-NEXT: [[TMP2:%.*]] = shl nuw nsw i32 [[ARG0]], 6
+; CHECK-NEXT: [[TMP3:%.*]] = getelementptr inbounds i8, ptr addrspace(3) [[TMP1]], i32 [[TMP2]]
+; CHECK-NEXT: [[TMP4:%.*]] = getelementptr inbounds i8, ptr addrspace(3) [[TMP3]], i32 [[ARG2]]
+; CHECK-NEXT: [[TMP5:%.*]] = getelementptr inbounds i8, ptr addrspace(3) [[TMP4]], i32 [[ARG3]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[ARG0]], 2
+; CHECK-NEXT: br i1 [[CMP]], [[DOTLR_PH:label %.*]], [[DOTEXIT_POINT:label %.*]]
+; CHECK: [[_LR_PH:.*:]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, ptr addrspace(3) [[TMP5]], i32 [[ARG4]]
+; CHECK-NEXT: [[TMP6:%.*]] = getelementptr inbounds i8, ptr addrspace(3) [[GEP]], i32 [[ARG5]]
+; CHECK-NEXT: [[TMP7:%.*]] = insertelement <8 x half> poison, half [[ARG6_HALF]], i32 0
+; CHECK-NEXT: [[TMP8:%.*]] = insertelement <8 x half> [[TMP7]], half 0xH0000, i32 1
+; CHECK-NEXT: [[TMP9:%.*]] = insertelement <8 x half> [[TMP8]], half 0xH0000, i32 2
+; CHECK-NEXT: [[TMP10:%.*]] = insertelement <8 x half> [[TMP9]], half 0xH0000, i32 3
+; CHECK-NEXT: [[TMP11:%.*]] = insertelement <8 x half> [[TMP10]], half 0xH0000, i32 4
+; CHECK-NEXT: [[TMP12:%.*]] = extractelement <2 x half> [[ARG8_2XHALF]], i32 0
+; CHECK-NEXT: [[TMP13:%.*]] = insertelement <8 x half> [[TMP11]], half [[TMP12]], i32 5
+; CHECK-NEXT: [[TMP14:%.*]] = extractelement <2 x half> [[ARG8_2XHALF]], i32 1
+; CHECK-NEXT: [[TMP15:%.*]] = insertelement <8 x half> [[TMP13]], half [[TMP14]], i32 6
+; CHECK-NEXT: [[TMP16:%.*]] = insertelement <8 x half> [[TMP15]], half [[ARG7_HALF]], i32 7
+; CHECK-NEXT: store <8 x half> [[TMP16]], ptr addrspace(3) [[TMP6]], align 2
+; CHECK-NEXT: br [[DOTEXIT_POINT]]
+; CHECK: [[_EXIT_POINT:.*:]]
+; CHECK-NEXT: ret void
+;
+ %base1 = getelementptr inbounds i8, ptr addrspace(3) %arg1_ptr, i32 458752
+ br label %.preheader11.preheader
+
+.preheader11.preheader:
+ %base2 = shl nuw nsw i32 %arg0, 6
+ %base3 = getelementptr inbounds i8, ptr addrspace(3) %base1, i32 %base2
+
+ %base4 = getelementptr inbounds i8, ptr addrspace(3) %base3, i32 %arg2
+ %base5 = getelementptr inbounds i8, ptr addrspace(3) %base4, i32 %arg3
+
+ %cmp = icmp sgt i32 %arg0, 2
+ br i1 %cmp, label %.lr.ph, label %.exit_point
+
+.lr.ph:
+ %gep = getelementptr inbounds i8, ptr addrspace(3) %base5, i32 %arg4
+
+ %dst = getelementptr inbounds i8, ptr addrspace(3) %gep, i32 %arg5
+ %dst_off2 = getelementptr inbounds i8, ptr addrspace(3) %dst, i32 2
+ %dst_off10 = getelementptr inbounds i8, ptr addrspace(3) %dst, i32 10
+ %dst_off14 = getelementptr inbounds i8, ptr addrspace(3) %dst, i32 14
+
+ store half %arg6_half, ptr addrspace(3) %dst, align 2
+ store <4 x half> zeroinitializer, ptr addrspace(3) %dst_off2, align 2
+ store <2 x half> %arg8_2xhalf, ptr addrspace(3) %dst_off10, align 2
+ store half %arg7_half, ptr addrspace(3) %dst_off14, align 2
+ br label %.exit_point
+
+.exit_point:
+ ret void
+}
More information about the llvm-commits
mailing list