[llvm] fc7cdaa - [GVN] Refactor handling of pointer-select in GVN pass
Sergey Kachkov via llvm-commits
llvm-commits at lists.llvm.org
Mon Jan 16 03:13:08 PST 2023
Author: Sergey Kachkov
Date: 2023-01-16T14:12:28+03:00
New Revision: fc7cdaa373308ce3d72218b4d80101ae19850a6c
URL: https://github.com/llvm/llvm-project/commit/fc7cdaa373308ce3d72218b4d80101ae19850a6c
DIFF: https://github.com/llvm/llvm-project/commit/fc7cdaa373308ce3d72218b4d80101ae19850a6c.diff
LOG: [GVN] Refactor handling of pointer-select in GVN pass
This patch introduces new type of memory dependency - Select to
consistently handle it like Def/Clobber dependency.
Differential Revision: https://reviews.llvm.org/D141619
Added:
Modified:
llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h
llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
llvm/lib/Transforms/Scalar/GVN.cpp
llvm/test/Transforms/GVN/PRE/pre-load-through-select.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h b/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h
index 24b4673a47e25..b99807a25b775 100644
--- a/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h
+++ b/llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h
@@ -79,6 +79,10 @@ class MemDepResult {
/// the calls are the same.
Def,
+ /// This marker indicates that the query has dependency from select
+ /// instruction.
+ Select,
+
/// This marker indicates that the query has no known dependency in the
/// specified block.
///
@@ -106,6 +110,7 @@ class MemDepResult {
DepType, PointerSumTypeMember<Invalid, Instruction *>,
PointerSumTypeMember<Clobber, Instruction *>,
PointerSumTypeMember<Def, Instruction *>,
+ PointerSumTypeMember<Select, Instruction *>,
PointerSumTypeMember<Other, PointerEmbeddedInt<OtherType, 3>>>;
ValueTy Value;
@@ -124,6 +129,9 @@ class MemDepResult {
assert(Inst && "Clobber requires inst");
return MemDepResult(ValueTy::create<Clobber>(Inst));
}
+ static MemDepResult getSelect(Instruction *Inst) {
+ return MemDepResult(ValueTy::create<Select>(Inst));
+ }
static MemDepResult getNonLocal() {
return MemDepResult(ValueTy::create<Other>(NonLocal));
}
@@ -142,6 +150,13 @@ class MemDepResult {
/// definition dependency.
bool isDef() const { return Value.is<Def>(); }
+ /// Tests if this MemDepResult represents a query that is an instruction
+ /// select dependency.
+ bool isSelect() const { return Value.is<Select>(); }
+
+ /// Tests if this MemDepResult represents a local query (Clobber/Def/Select).
+ bool isLocal() const { return isClobber() || isDef() || isSelect(); }
+
/// Tests if this MemDepResult represents a query that is transparent to the
/// start of the block, but where a non-local hasn't been done.
bool isNonLocal() const {
@@ -170,6 +185,8 @@ class MemDepResult {
return Value.cast<Clobber>();
case Def:
return Value.cast<Def>();
+ case Select:
+ return Value.cast<Select>();
case Other:
return nullptr;
}
diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index 7a13e7a641f32..960679ba56f79 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -592,6 +592,11 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
return MemDepResult::getDef(Inst);
}
+ // If we found a select instruction for MemLoc pointer, return it as
+ // Select dependency.
+ if (isa<SelectInst>(Inst) && MemLoc.Ptr == Inst)
+ return MemDepResult::getSelect(Inst);
+
if (isInvariantLoad)
continue;
@@ -962,7 +967,7 @@ MemDepResult MemoryDependenceResults::getNonLocalInfoForBlock(
// If the block has a dependency (i.e. it isn't completely transparent to
// the value), remember the reverse association because we just added it
// to Cache!
- if (!Dep.isDef() && !Dep.isClobber())
+ if (!Dep.isLocal())
return Dep;
// Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index f9fdd7783820b..e542efb45e269 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1120,31 +1120,26 @@ static void reportMayClobberedLoad(LoadInst *Load, MemDepResult DepInfo,
/// 1. The pointer select (\p Address) must be defined in \p DepBB.
/// 2. Both value operands of the pointer select must be loaded in the same
/// basic block, before the pointer select.
-/// 3. There must be no instructions between the found loads and \p End that may
+/// 3. There must be no instructions between the found loads and \p Sel that may
/// clobber the loads.
static std::optional<AvailableValue>
-tryToConvertLoadOfPtrSelect(BasicBlock *DepBB, BasicBlock::iterator End,
- Value *Address, Type *LoadTy, DominatorTree &DT,
+tryToConvertLoadOfPtrSelect(SelectInst *Sel, Type *LoadTy, DominatorTree &DT,
AAResults *AA) {
-
- auto *Sel = dyn_cast_or_null<SelectInst>(Address);
- if (!Sel || DepBB != Sel->getParent())
- return std::nullopt;
-
LoadInst *L1 = findDominatingLoad(Sel->getOperand(1), LoadTy, Sel, DT);
LoadInst *L2 = findDominatingLoad(Sel->getOperand(2), LoadTy, Sel, DT);
if (!L1 || !L2)
return std::nullopt;
// Ensure there are no accesses that may modify the locations referenced by
- // either L1 or L2 between L1, L2 and the specified End iterator.
+ // either L1 or L2 between L1, L2 and the specified Sel instruction.
Instruction *EarlierLoad = L1->comesBefore(L2) ? L1 : L2;
MemoryLocation L1Loc = MemoryLocation::get(L1);
MemoryLocation L2Loc = MemoryLocation::get(L2);
- if (any_of(make_range(EarlierLoad->getIterator(), End), [&](Instruction &I) {
- return isModSet(AA->getModRefInfo(&I, L1Loc)) ||
- isModSet(AA->getModRefInfo(&I, L2Loc));
- }))
+ if (any_of(make_range(EarlierLoad->getIterator(), Sel->getIterator()),
+ [&](Instruction &I) {
+ return isModSet(AA->getModRefInfo(&I, L1Loc)) ||
+ isModSet(AA->getModRefInfo(&I, L2Loc));
+ }))
return std::nullopt;
return AvailableValue::getSelect(Sel);
@@ -1153,20 +1148,21 @@ tryToConvertLoadOfPtrSelect(BasicBlock *DepBB, BasicBlock::iterator End,
std::optional<AvailableValue>
GVNPass::AnalyzeLoadAvailability(LoadInst *Load, MemDepResult DepInfo,
Value *Address) {
- if (!DepInfo.isDef() && !DepInfo.isClobber()) {
- assert(isa<SelectInst>(Address));
- return tryToConvertLoadOfPtrSelect(Load->getParent(), Load->getIterator(),
- Address, Load->getType(),
- getDominatorTree(), getAliasAnalysis());
- }
-
- assert((DepInfo.isDef() || DepInfo.isClobber()) &&
- "expected a local dependence");
assert(Load->isUnordered() && "rules below are incorrect for ordered access");
-
- const DataLayout &DL = Load->getModule()->getDataLayout();
+ assert(DepInfo.isLocal() && "expected a local dependence");
Instruction *DepInst = DepInfo.getInst();
+ if (DepInfo.isSelect()) {
+ // Check if load with Addr dependent from select can be converted to select
+ // between load values. There must be no instructions between the found
+ // loads and DepInst that may clobber the loads.
+ assert(isa<SelectInst>(DepInst) && "Dependency must be select instruction");
+ auto *Sel = cast<SelectInst>(DepInst);
+ return tryToConvertLoadOfPtrSelect(Sel, Load->getType(), getDominatorTree(),
+ getAliasAnalysis());
+ }
+
+ const DataLayout &DL = Load->getModule()->getDataLayout();
if (DepInfo.isClobber()) {
// If the dependence is to a store that writes to a superset of the bits
// read by the load, we can extract the bits we need for the load from the
@@ -1298,24 +1294,15 @@ void GVNPass::AnalyzeLoadAvailability(LoadInst *Load, LoadDepVect &Deps,
continue;
}
- // The address being loaded in this non-local block may not be the same as
- // the pointer operand of the load if PHI translation occurs. Make sure
- // to consider the right address.
- Value *Address = Dep.getAddress();
-
- if (!DepInfo.isDef() && !DepInfo.isClobber()) {
- if (auto R = tryToConvertLoadOfPtrSelect(
- DepBB, DepBB->end(), Address, Load->getType(), getDominatorTree(),
- getAliasAnalysis())) {
- ValuesPerBlock.push_back(
- AvailableValueInBlock::get(DepBB, std::move(*R)));
- continue;
- }
+ if (!DepInfo.isLocal()) {
UnavailableBlocks.push_back(DepBB);
continue;
}
- if (auto AV = AnalyzeLoadAvailability(Load, DepInfo, Address)) {
+ // The address being loaded in this non-local block may not be the same as
+ // the pointer operand of the load if PHI translation occurs. Make sure
+ // to consider the right address.
+ if (auto AV = AnalyzeLoadAvailability(Load, DepInfo, Dep.getAddress())) {
// subtlety: because we know this was a non-local dependency, we know
// it's safe to materialize anywhere between the instruction within
// DepInfo and the end of it's block.
@@ -2043,9 +2030,8 @@ bool GVNPass::processLoad(LoadInst *L) {
if (Dep.isNonLocal())
return processNonLocalLoad(L);
- Value *Address = L->getPointerOperand();
// Only handle the local case below
- if (!Dep.isDef() && !Dep.isClobber() && !isa<SelectInst>(Address)) {
+ if (!Dep.isLocal()) {
// This might be a NonFuncLocal or an Unknown
LLVM_DEBUG(
// fast print dep, using operator<< on instruction is too slow.
@@ -2054,7 +2040,7 @@ bool GVNPass::processLoad(LoadInst *L) {
return false;
}
- auto AV = AnalyzeLoadAvailability(L, Dep, Address);
+ auto AV = AnalyzeLoadAvailability(L, Dep, L->getPointerOperand());
if (!AV)
return false;
diff --git a/llvm/test/Transforms/GVN/PRE/pre-load-through-select.ll b/llvm/test/Transforms/GVN/PRE/pre-load-through-select.ll
index af1a13a1cbbb8..e53aa97269207 100644
--- a/llvm/test/Transforms/GVN/PRE/pre-load-through-select.ll
+++ b/llvm/test/Transforms/GVN/PRE/pre-load-through-select.ll
@@ -236,13 +236,15 @@ define i32 @test_pointer_phi_select_simp_store_clobber_3(ptr %a, ptr %b, ptr %c,
; CHECK-NEXT: [[L_1:%.*]] = load i32, ptr [[A:%.*]], align 4
; CHECK-NEXT: [[L_2:%.*]] = load i32, ptr [[B:%.*]], align 4
; CHECK-NEXT: [[CMP_I_I_I:%.*]] = icmp ult i32 [[L_1]], [[L_2]]
+; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[CMP_I_I_I]], i32 [[L_1]], i32 [[L_2]]
; CHECK-NEXT: [[MIN_SELECT:%.*]] = select i1 [[CMP_I_I_I]], ptr [[A]], ptr [[B]]
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: else:
+; CHECK-NEXT: [[RES_2_PRE:%.*]] = load i32, ptr [[A]], align 4
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
+; CHECK-NEXT: [[RES_2:%.*]] = phi i32 [ [[SELECT]], [[THEN]] ], [ [[RES_2_PRE]], [[ELSE]] ]
; CHECK-NEXT: [[P:%.*]] = phi ptr [ [[MIN_SELECT]], [[THEN]] ], [ [[A]], [[ELSE]] ]
-; CHECK-NEXT: [[RES_2:%.*]] = load i32, ptr [[P]], align 4
; CHECK-NEXT: ret i32 [[RES_2]]
;
entry:
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