[llvm] [GVN] Restrict equality propagation for pointers (PR #82458)
Usman Nadeem via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 20 20:14:34 PST 2024
https://github.com/UsmanNadeem created https://github.com/llvm/llvm-project/pull/82458
Reviving https://reviews.llvm.org/D143129
This patch does the following:
Adds the following functions:
- replaceDominatedUsesWithIf() that takes a callback.
- canReplacePointersIfEqual(...) returns true if the underlying object
is the same, and for null and const dereferencable pointer replacements.
- canReplacePointersIfEqualInUse(...) returns true for the above as well
as if the use is in icmp/ptrtoint or phi/selects feeding into them.
Updates GVN using the functions above so that the pointer replacements
are only made using the above API.
Change-Id: I4927ea452734458be028854ef0e5cbcd81955910
>From e7d702492e8e986606c3290395a2f04bdf463365 Mon Sep 17 00:00:00 2001
From: "Nadeem, Usman" <mnadeem at quicinc.com>
Date: Thu, 10 Aug 2023 17:33:08 -0700
Subject: [PATCH] [GVN] Restrict equality propagation for pointers
Reviving https://reviews.llvm.org/D143129
This patch does the following:
Adds the following functions:
- replaceDominatedUsesWithIf() that takes a callback.
- canReplacePointersIfEqual(...) returns true if the underlying object
is the same, and for null and const dereferencable pointer replacements.
- canReplacePointersIfEqualInUse(...) returns true for the above as well
as if the use is in icmp/ptrtoint or phi/selects feeding into them.
Updates GVN using the functions above so that the pointer replacements
are only made using the above API.
Change-Id: I4927ea452734458be028854ef0e5cbcd81955910
---
llvm/include/llvm/Analysis/Loads.h | 15 +-
llvm/include/llvm/Transforms/Utils/Local.h | 12 ++
llvm/lib/Analysis/Loads.cpp | 78 ++++++--
llvm/lib/Transforms/Scalar/GVN.cpp | 24 ++-
llvm/lib/Transforms/Utils/Local.cpp | 30 ++-
llvm/test/Transforms/GVN/condprop.ll | 207 ++++++++++++++++++++-
llvm/unittests/Analysis/LoadsTest.cpp | 49 +++--
7 files changed, 354 insertions(+), 61 deletions(-)
diff --git a/llvm/include/llvm/Analysis/Loads.h b/llvm/include/llvm/Analysis/Loads.h
index 0926093bba99de..e39a1d6cafad23 100644
--- a/llvm/include/llvm/Analysis/Loads.h
+++ b/llvm/include/llvm/Analysis/Loads.h
@@ -173,14 +173,15 @@ Value *findAvailablePtrLoadStore(const MemoryLocation &Loc, Type *AccessTy,
unsigned MaxInstsToScan, BatchAAResults *AA,
bool *IsLoadCSE, unsigned *NumScanedInst);
-/// Returns true if a pointer value \p A can be replace with another pointer
-/// value \B if they are deemed equal through some means (e.g. information from
+/// Returns true if a pointer value \p From can be replaced with another pointer
+/// value \To if they are deemed equal through some means (e.g. information from
/// conditions).
-/// NOTE: the current implementations is incomplete and unsound. It does not
-/// reject all invalid cases yet, but will be made stricter in the future. In
-/// particular this means returning true means unknown if replacement is safe.
-bool canReplacePointersIfEqual(Value *A, Value *B, const DataLayout &DL,
- Instruction *CtxI);
+/// NOTE: The current implementation allows replacement in Icmp and PtrToInt
+/// instructions, as well as when we are replacing with a null pointer.
+/// Additionally it also allows replacement of pointers when both pointers have
+/// the same underlying object.
+bool canReplacePointersIfEqual(const Value *From, const Value *To);
+bool canReplacePointersInUseIfEqual(const Use &U, const Value *To);
}
#endif
diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index 2df3c9049c7d62..d0dbf1951fe8b6 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -432,6 +432,18 @@ unsigned replaceDominatedUsesWith(Value *From, Value *To, DominatorTree &DT,
/// the end of the given BasicBlock. Returns the number of replacements made.
unsigned replaceDominatedUsesWith(Value *From, Value *To, DominatorTree &DT,
const BasicBlock *BB);
+/// Replace each use of 'From' with 'To' if that use is dominated by
+/// the given edge and the callback ShouldReplace returns true. Returns the
+/// number of replacements made.
+unsigned replaceDominatedUsesWithIf(
+ Value *From, Value *To, DominatorTree &DT, const BasicBlockEdge &Edge,
+ function_ref<bool(const Use &U, const Value *To)> ShouldReplace);
+/// Replace each use of 'From' with 'To' if that use is dominated by
+/// the end of the given BasicBlock and the callback ShouldReplace returns true.
+/// Returns the number of replacements made.
+unsigned replaceDominatedUsesWithIf(
+ Value *From, Value *To, DominatorTree &DT, const BasicBlock *BB,
+ function_ref<bool(const Use &U, const Value *To)> ShouldReplace);
/// Return true if this call calls a gc leaf function.
///
diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index 6bf0d2f56eb4eb..e7d72fbc7107d6 100644
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -708,22 +708,66 @@ Value *llvm::FindAvailableLoadedValue(LoadInst *Load, BatchAAResults &AA,
return Available;
}
-bool llvm::canReplacePointersIfEqual(Value *A, Value *B, const DataLayout &DL,
- Instruction *CtxI) {
- Type *Ty = A->getType();
- assert(Ty == B->getType() && Ty->isPointerTy() &&
- "values must have matching pointer types");
-
- // NOTE: The checks in the function are incomplete and currently miss illegal
- // cases! The current implementation is a starting point and the
- // implementation should be made stricter over time.
- if (auto *C = dyn_cast<Constant>(B)) {
- // Do not allow replacing a pointer with a constant pointer, unless it is
- // either null or at least one byte is dereferenceable.
- APInt OneByte(DL.getPointerTypeSizeInBits(Ty), 1);
- return C->isNullValue() ||
- isDereferenceableAndAlignedPointer(B, Align(1), OneByte, DL, CtxI);
- }
+// Returns true if a use is either in an ICmp/PtrToInt or a Phi/Select that only
+// feeds into them.
+static bool isPointerUseReplacable(const Use &U, int MaxLookup = 6) {
+ if (MaxLookup == 0)
+ return false;
+
+ const User *User = U.getUser();
+ if (isa<ICmpInst>(User))
+ return true;
+ if (isa<PtrToIntInst>(User))
+ return true;
+ if (isa<PHINode, SelectInst>(User) &&
+ all_of(User->uses(), [&](const Use &Use) {
+ return isPointerUseReplacable(Use, MaxLookup - 1);
+ }))
+ return true;
+
+ return false;
+}
+
+static const DataLayout &getDLFromVal(const Value *V) {
+ if (const Argument *A = dyn_cast<Argument>(V))
+ return A->getParent()->getParent()->getDataLayout();
+ if (const Instruction *I = dyn_cast<Instruction>(V))
+ return I->getModule()->getDataLayout();
+ if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
+ return GV->getParent()->getDataLayout();
+ llvm_unreachable("Unknown Value type");
+}
+
+// Returns true if `To` is a null pointer, constant dereferenceable pointer or
+// both pointers have the same underlying objects.
+static bool isPointerAlwaysReplacable(const Value *From, const Value *To) {
+ if (isa<ConstantPointerNull>(To))
+ return true;
+ if (isa<Constant>(To) &&
+ isDereferenceablePointer(To, Type::getInt8Ty(To->getContext()),
+ getDLFromVal(From)))
+ return true;
+ if (getUnderlyingObject(From) == getUnderlyingObject(To))
+ return true;
+ return false;
+}
+
+bool llvm::canReplacePointersInUseIfEqual(const Use &U, const Value *To) {
+ assert(U->getType() == To->getType() && "values must have matching types");
+ // Not a pointer, just return true.
+ if (!To->getType()->isPointerTy())
+ return true;
+
+ if (isPointerAlwaysReplacable(&*U, To))
+ return true;
+ return isPointerUseReplacable(U);
+}
+
+bool llvm::canReplacePointersIfEqual(const Value *From, const Value *To) {
+ assert(From->getType() == To->getType() && "values must have matching types");
+ // Not a pointer, just return true.
+ if (!From->getType()->isPointerTy())
+ return true;
- return true;
+ return isPointerAlwaysReplacable(From, To);
}
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index dcb1ed334b6103..d4b16836d728fa 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -33,6 +33,7 @@
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/InstructionPrecedenceTracking.h"
#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
@@ -2443,7 +2444,8 @@ bool GVNPass::propagateEquality(Value *LHS, Value *RHS,
// using the leader table is about compiling faster, not optimizing better).
// The leader table only tracks basic blocks, not edges. Only add to if we
// have the simple case where the edge dominates the end.
- if (RootDominatesEnd && !isa<Instruction>(RHS))
+ if (RootDominatesEnd && !isa<Instruction>(RHS) &&
+ canReplacePointersIfEqual(LHS, RHS))
addToLeaderTable(LVN, RHS, Root.getEnd());
// Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope. As
@@ -2452,14 +2454,18 @@ bool GVNPass::propagateEquality(Value *LHS, Value *RHS,
if (!LHS->hasOneUse()) {
unsigned NumReplacements =
DominatesByEdge
- ? replaceDominatedUsesWith(LHS, RHS, *DT, Root)
- : replaceDominatedUsesWith(LHS, RHS, *DT, Root.getStart());
-
- Changed |= NumReplacements > 0;
- NumGVNEqProp += NumReplacements;
- // Cached information for anything that uses LHS will be invalid.
- if (MD)
- MD->invalidateCachedPointerInfo(LHS);
+ ? replaceDominatedUsesWithIf(LHS, RHS, *DT, Root,
+ canReplacePointersInUseIfEqual)
+ : replaceDominatedUsesWithIf(LHS, RHS, *DT, Root.getStart(),
+ canReplacePointersInUseIfEqual);
+
+ if (NumReplacements > 0) {
+ Changed = true;
+ NumGVNEqProp += NumReplacements;
+ // Cached information for anything that uses LHS will be invalid.
+ if (MD)
+ MD->invalidateCachedPointerInfo(LHS);
+ }
}
// Now try to deduce additional equalities from this one. For example, if
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index e4aa25f7ac6ad3..dcea7bb42c54e9 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -3389,15 +3389,18 @@ void llvm::patchReplacementInstruction(Instruction *I, Value *Repl) {
}
template <typename RootType, typename DominatesFn>
-static unsigned replaceDominatedUsesWith(Value *From, Value *To,
- const RootType &Root,
- const DominatesFn &Dominates) {
+static unsigned replaceDominatedUsesWith(
+ Value *From, Value *To, const RootType &Root, const DominatesFn &Dominates,
+ std::optional<function_ref<bool(const Use &U, const Value *To)>>
+ ShouldReplace) {
assert(From->getType() == To->getType());
unsigned Count = 0;
for (Use &U : llvm::make_early_inc_range(From->uses())) {
if (!Dominates(Root, U))
continue;
+ if (ShouldReplace.has_value() && !ShouldReplace.value()(U, To))
+ continue;
LLVM_DEBUG(dbgs() << "Replace dominated use of '";
From->printAsOperand(dbgs());
dbgs() << "' with " << *To << " in " << *U.getUser() << "\n");
@@ -3428,7 +3431,7 @@ unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
auto Dominates = [&DT](const BasicBlockEdge &Root, const Use &U) {
return DT.dominates(Root, U);
};
- return ::replaceDominatedUsesWith(From, To, Root, Dominates);
+ return ::replaceDominatedUsesWith(From, To, Root, Dominates, std::nullopt);
}
unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
@@ -3437,9 +3440,26 @@ unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
auto Dominates = [&DT](const BasicBlock *BB, const Use &U) {
return DT.dominates(BB, U);
};
- return ::replaceDominatedUsesWith(From, To, BB, Dominates);
+ return ::replaceDominatedUsesWith(From, To, BB, Dominates, std::nullopt);
+}
+
+unsigned llvm::replaceDominatedUsesWithIf(
+ Value *From, Value *To, DominatorTree &DT, const BasicBlockEdge &Root,
+ function_ref<bool(const Use &U, const Value *To)> ShouldReplace) {
+ auto Dominates = [&DT](const BasicBlockEdge &Root, const Use &U) {
+ return DT.dominates(Root, U);
+ };
+ return ::replaceDominatedUsesWith(From, To, Root, Dominates, ShouldReplace);
}
+unsigned llvm::replaceDominatedUsesWithIf(
+ Value *From, Value *To, DominatorTree &DT, const BasicBlock *BB,
+ function_ref<bool(const Use &U, const Value *To)> ShouldReplace) {
+ auto Dominates = [&DT](const BasicBlock *BB, const Use &U) {
+ return DT.dominates(BB, U);
+ };
+ return ::replaceDominatedUsesWith(From, To, BB, Dominates, ShouldReplace);
+}
bool llvm::callsGCLeafFunction(const CallBase *Call,
const TargetLibraryInfo &TLI) {
// Check if the function is specifically marked as a gc leaf function.
diff --git a/llvm/test/Transforms/GVN/condprop.ll b/llvm/test/Transforms/GVN/condprop.ll
index 6b1e4d10601099..2b202b1701150e 100644
--- a/llvm/test/Transforms/GVN/condprop.ll
+++ b/llvm/test/Transforms/GVN/condprop.ll
@@ -521,15 +521,16 @@ define i32 @test13(ptr %ptr1, ptr %ptr2) {
; CHECK-NEXT: [[GEP1:%.*]] = getelementptr i32, ptr [[PTR2:%.*]], i32 1
; CHECK-NEXT: [[GEP2:%.*]] = getelementptr i32, ptr [[PTR2]], i32 2
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[PTR1:%.*]], [[PTR2]]
-; CHECK-NEXT: [[VAL2_PRE:%.*]] = load i32, ptr [[GEP2]], align 4
; CHECK-NEXT: br i1 [[CMP]], label [[IF:%.*]], label [[END:%.*]]
; CHECK: if:
+; CHECK-NEXT: [[VAL1:%.*]] = load i32, ptr [[GEP2]], align 4
; CHECK-NEXT: br label [[END]]
; CHECK: end:
-; CHECK-NEXT: [[PHI1:%.*]] = phi ptr [ [[PTR2]], [[IF]] ], [ [[GEP1]], [[ENTRY:%.*]] ]
-; CHECK-NEXT: [[PHI2:%.*]] = phi i32 [ [[VAL2_PRE]], [[IF]] ], [ 0, [[ENTRY]] ]
+; CHECK-NEXT: [[PHI1:%.*]] = phi ptr [ [[PTR1]], [[IF]] ], [ [[GEP1]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[PHI2:%.*]] = phi i32 [ [[VAL1]], [[IF]] ], [ 0, [[ENTRY]] ]
; CHECK-NEXT: store i32 0, ptr [[PHI1]], align 4
-; CHECK-NEXT: [[RET:%.*]] = add i32 [[PHI2]], [[VAL2_PRE]]
+; CHECK-NEXT: [[VAL2:%.*]] = load i32, ptr [[GEP2]], align 4
+; CHECK-NEXT: [[RET:%.*]] = add i32 [[PHI2]], [[VAL2]]
; CHECK-NEXT: ret i32 [[RET]]
;
entry:
@@ -574,7 +575,7 @@ define void @test14(ptr %ptr1, ptr noalias %ptr2) {
; CHECK: if2:
; CHECK-NEXT: br label [[LOOP_END]]
; CHECK: loop.end:
-; CHECK-NEXT: [[PHI3:%.*]] = phi ptr [ [[PTR2]], [[THEN]] ], [ [[PTR1]], [[IF2]] ]
+; CHECK-NEXT: [[PHI3:%.*]] = phi ptr [ [[GEP2]], [[THEN]] ], [ [[PTR1]], [[IF2]] ]
; CHECK-NEXT: [[VAL3]] = load i32, ptr [[GEP2]], align 4
; CHECK-NEXT: store i32 [[VAL3]], ptr [[PHI3]], align 4
; CHECK-NEXT: br i1 undef, label [[LOOP]], label [[IF1]]
@@ -609,3 +610,199 @@ loop.end:
%gep3 = getelementptr inbounds i32, ptr %ptr1, i32 1
br i1 undef, label %loop, label %if1
}
+
+; Make sure that the call to use_ptr does not have %p1
+define void @single_phi1(ptr %p1) {
+; CHECK-LABEL: @single_phi1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr poison, align 8
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq ptr [[P2]], [[P1:%.*]]
+; CHECK-NEXT: br i1 [[CMP1]], label [[BB4:%.*]], label [[BB1:%.*]]
+; CHECK: bb1:
+; CHECK-NEXT: switch i8 poison, label [[BB2:%.*]] [
+; CHECK-NEXT: i8 0, label [[BB1]]
+; CHECK-NEXT: i8 1, label [[BB3:%.*]]
+; CHECK-NEXT: ]
+; CHECK: bb2:
+; CHECK-NEXT: unreachable
+; CHECK: bb3:
+; CHECK-NEXT: br label [[BB4]]
+; CHECK: bb4:
+; CHECK-NEXT: call void @use_bool(i1 [[CMP1]])
+; CHECK-NEXT: call void @use_ptr(ptr [[P2]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %p2 = load ptr, ptr poison, align 8
+ %cmp1 = icmp eq ptr %p2, %p1
+ br i1 %cmp1, label %bb4, label %bb1
+
+bb1:
+ switch i8 poison, label %bb2 [
+ i8 0, label %bb1
+ i8 1, label %bb3
+ ]
+
+bb2:
+ unreachable
+
+bb3:
+ br label %bb4
+
+bb4:
+ %phi1 = phi ptr [ %p2, %entry ], [ poison, %bb3 ]
+ %cmp2 = icmp eq ptr %phi1, %p1
+ call void @use_bool(i1 %cmp2)
+ call void @use_ptr(ptr %phi1)
+ ret void
+}
+
+define void @single_phi2(ptr %p1) {
+; CHECK-LABEL: @single_phi2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr poison, align 8
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq ptr [[P2]], [[P1:%.*]]
+; CHECK-NEXT: br i1 [[CMP1]], label [[BB4:%.*]], label [[BB1:%.*]]
+; CHECK: bb1:
+; CHECK-NEXT: switch i8 poison, label [[BB2:%.*]] [
+; CHECK-NEXT: i8 0, label [[BB1]]
+; CHECK-NEXT: i8 1, label [[BB3:%.*]]
+; CHECK-NEXT: ]
+; CHECK: bb2:
+; CHECK-NEXT: br label [[BB4]]
+; CHECK: bb3:
+; CHECK-NEXT: br label [[BB4]]
+; CHECK: bb4:
+; CHECK-NEXT: call void @use_bool(i1 [[CMP1]])
+; CHECK-NEXT: call void @use_ptr(ptr [[P2]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %p2 = load ptr, ptr poison, align 8
+ %cmp1 = icmp eq ptr %p2, %p1
+ br i1 %cmp1, label %bb4, label %bb1
+
+bb1:
+ switch i8 poison, label %bb2 [
+ i8 0, label %bb1
+ i8 1, label %bb3
+ ]
+
+bb2:
+ br label %bb4
+
+bb3:
+ br label %bb4
+
+bb4:
+ %phi1 = phi ptr [ %p2, %entry ], [ %p2, %bb2 ], [ poison, %bb3 ]
+ %cmp2 = icmp eq ptr %phi1, %p1
+ call void @use_bool(i1 %cmp2)
+ call void @use_ptr(ptr %phi1)
+ ret void
+}
+
+define void @multiple_phi1(ptr %p1) {
+; CHECK-LABEL: @multiple_phi1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr poison, align 8
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq ptr [[P2]], [[P1:%.*]]
+; CHECK-NEXT: br i1 [[CMP1]], label [[BB4:%.*]], label [[BB1:%.*]]
+; CHECK: bb1:
+; CHECK-NEXT: switch i8 poison, label [[BB2:%.*]] [
+; CHECK-NEXT: i8 0, label [[BB1]]
+; CHECK-NEXT: i8 1, label [[BB3:%.*]]
+; CHECK-NEXT: ]
+; CHECK: bb2:
+; CHECK-NEXT: unreachable
+; CHECK: bb3:
+; CHECK-NEXT: br label [[BB4]]
+; CHECK: bb4:
+; CHECK-NEXT: call void @use_bool(i1 [[CMP1]])
+; CHECK-NEXT: br label [[BB5:%.*]]
+; CHECK: bb5:
+; CHECK-NEXT: call void @use_ptr(ptr [[P2]])
+; CHECK-NEXT: br label [[BB5]]
+;
+entry:
+ %p2 = load ptr, ptr poison, align 8
+ %cmp1 = icmp eq ptr %p2, %p1
+ br i1 %cmp1, label %bb4, label %bb1
+
+bb1:
+ switch i8 poison, label %bb2 [
+ i8 0, label %bb1
+ i8 1, label %bb3
+ ]
+
+bb2:
+ unreachable
+
+bb3:
+ br label %bb4
+
+bb4:
+ %phi1 = phi ptr [ %p2, %entry ], [ poison, %bb3 ]
+ %cmp2 = icmp eq ptr %phi1, %p1
+ call void @use_bool(i1 %cmp2)
+ br label %bb5
+
+bb5:
+ %phi2 = phi ptr [ poison, %bb5 ], [ %phi1, %bb4 ]
+ call void @use_ptr(ptr %phi2)
+ br label %bb5
+}
+
+define void @multiple_phi2(ptr %p1) {
+; CHECK-LABEL: @multiple_phi2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[P2:%.*]] = load ptr, ptr poison, align 8
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq ptr [[P2]], [[P1:%.*]]
+; CHECK-NEXT: br i1 [[CMP1]], label [[BB4:%.*]], label [[BB1:%.*]]
+; CHECK: bb1:
+; CHECK-NEXT: switch i8 poison, label [[BB2:%.*]] [
+; CHECK-NEXT: i8 0, label [[BB1]]
+; CHECK-NEXT: i8 1, label [[BB3:%.*]]
+; CHECK-NEXT: ]
+; CHECK: bb2:
+; CHECK-NEXT: br label [[BB4]]
+; CHECK: bb3:
+; CHECK-NEXT: br label [[BB4]]
+; CHECK: bb4:
+; CHECK-NEXT: call void @use_bool(i1 [[CMP1]])
+; CHECK-NEXT: br label [[BB5:%.*]]
+; CHECK: bb5:
+; CHECK-NEXT: call void @use_ptr(ptr [[P2]])
+; CHECK-NEXT: br label [[BB5]]
+;
+entry:
+ %p2 = load ptr, ptr poison, align 8
+ %cmp1 = icmp eq ptr %p2, %p1
+ br i1 %cmp1, label %bb4, label %bb1
+
+bb1:
+ switch i8 poison, label %bb2 [
+ i8 0, label %bb1
+ i8 1, label %bb3
+ ]
+
+bb2:
+ br label %bb4
+
+bb3:
+ br label %bb4
+
+bb4:
+ %phi1 = phi ptr [ %p2, %entry ], [ %p2, %bb2 ], [ poison, %bb3 ]
+ %cmp2 = icmp eq ptr %phi1, %p1
+ call void @use_bool(i1 %cmp2)
+ br label %bb5
+
+bb5:
+ %phi2 = phi ptr [ poison, %bb5 ], [ %phi1, %bb4 ]
+ call void @use_ptr(ptr %phi2)
+ br label %bb5
+}
+
+declare void @use_bool(i1)
+declare void @use_ptr(ptr)
diff --git a/llvm/unittests/Analysis/LoadsTest.cpp b/llvm/unittests/Analysis/LoadsTest.cpp
index 0111cfeefa41ae..0694889596fa23 100644
--- a/llvm/unittests/Analysis/LoadsTest.cpp
+++ b/llvm/unittests/Analysis/LoadsTest.cpp
@@ -68,35 +68,48 @@ TEST(LoadsTest, CanReplacePointersIfEqual) {
R"IR(
@y = common global [1 x i32] zeroinitializer, align 4
@x = common global [1 x i32] zeroinitializer, align 4
-
declare void @use(i32*)
-define void @f(i32* %p) {
+define void @f(i32* %p1, i32* %p2, i64 %i) {
call void @use(i32* getelementptr inbounds ([1 x i32], [1 x i32]* @y, i64 0, i64 0))
- call void @use(i32* getelementptr inbounds (i32, i32* getelementptr inbounds ([1 x i32], [1 x i32]* @x, i64 0, i64 0), i64 1))
+
+ %p1_idx = getelementptr inbounds i32, i32* %p1, i64 %i
+ call void @use(i32* %p1_idx)
+
+ %icmp = icmp eq i32* %p1, getelementptr inbounds ([1 x i32], [1 x i32]* @y, i64 0, i64 0)
+ %ptrInt = ptrtoint i32* %p1 to i64
ret void
}
)IR");
- const auto &DL = M->getDataLayout();
auto *GV = M->getNamedValue("f");
ASSERT_TRUE(GV);
auto *F = dyn_cast<Function>(GV);
ASSERT_TRUE(F);
- // NOTE: the implementation of canReplacePointersIfEqual is incomplete.
- // Currently the only the cases it returns false for are really sound and
- // returning true means unknown.
- Value *P = &*F->arg_begin();
+ Value *P1 = &*F->arg_begin();
+ Value *P2 = F->getArg(1);
+ Value *NullPtr = Constant::getNullValue(P1->getType());
auto InstIter = F->front().begin();
- Value *ConstDerefPtr = *cast<CallInst>(&*InstIter)->arg_begin();
- // ConstDerefPtr is a constant pointer that is provably de-referenceable. We
- // can replace an arbitrary pointer with it.
- EXPECT_TRUE(canReplacePointersIfEqual(P, ConstDerefPtr, DL, nullptr));
+ CallInst *UserOfY = cast<CallInst>(&*InstIter);
+ Value *ConstDerefPtr = UserOfY->getArgOperand(0);
+ // We cannot replace two pointers in arbitrary instructions unless we are
+ // replacing with null, a constant dereferencable pointer or they have the
+ // same underlying object.
+ EXPECT_FALSE(canReplacePointersIfEqual(ConstDerefPtr, P1));
+ EXPECT_FALSE(canReplacePointersIfEqual(P1, P2));
+ EXPECT_TRUE(canReplacePointersIfEqual(P1, ConstDerefPtr));
+ EXPECT_TRUE(canReplacePointersIfEqual(P1, NullPtr));
+
+ GetElementPtrInst *BasedOnP1 = cast<GetElementPtrInst>(&*++InstIter);
+ EXPECT_TRUE(canReplacePointersIfEqual(BasedOnP1, P1));
+ EXPECT_FALSE(canReplacePointersIfEqual(BasedOnP1, P2));
- ++InstIter;
- Value *ConstUnDerefPtr = *cast<CallInst>(&*InstIter)->arg_begin();
- // ConstUndDerefPtr is a constant pointer that is provably not
- // de-referenceable. We cannot replace an arbitrary pointer with it.
- EXPECT_FALSE(
- canReplacePointersIfEqual(ConstDerefPtr, ConstUnDerefPtr, DL, nullptr));
+ // // We can replace two arbitrary pointers in icmp and ptrtoint instructions.
+ auto P1UseIter = P1->use_begin();
+ const Use &PtrToIntUse = *P1UseIter;
+ const Use &IcmpUse = *++P1UseIter;
+ const Use &GEPUse = *++P1UseIter;
+ EXPECT_FALSE(canReplacePointersInUseIfEqual(GEPUse, P2));
+ EXPECT_TRUE(canReplacePointersInUseIfEqual(PtrToIntUse, P2));
+ EXPECT_TRUE(canReplacePointersInUseIfEqual(IcmpUse, P2));
}
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