[llvm] 438a81a - [Function Specialisation] Fix use after free
Alexandros Lamprineas via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 2 08:32:49 PST 2022
Author: Alexandros Lamprineas
Date: 2022-02-02T16:32:10Z
New Revision: 438a81a2847f615c8c6236b59096393c9d285e00
URL: https://github.com/llvm/llvm-project/commit/438a81a2847f615c8c6236b59096393c9d285e00
DIFF: https://github.com/llvm/llvm-project/commit/438a81a2847f615c8c6236b59096393c9d285e00.diff
LOG: [Function Specialisation] Fix use after free
This is a fix for a use-after-free found by the address sanitizer when
compiling GCC: https://github.com/llvm/llvm-project/issues/52821
The Function Specialization pass may remove instructions, cached
inside the PredicateBase class, which are later being dereferenced
from the SCCPInstVisitor class. To prevent the dangling references
I am lazily deleting the dead instructions after the Solver has run.
Differential Revision: https://reviews.llvm.org/D118591
Added:
llvm/test/Transforms/FunctionSpecialization/bug52821-use-after-free.ll
Modified:
llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
index 6c3cc3914337..9b6246b380bf 100644
--- a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
@@ -276,6 +276,7 @@ class FunctionSpecializer {
std::function<TargetLibraryInfo &(Function &)> GetTLI;
SmallPtrSet<Function *, 2> SpecializedFuncs;
+ SmallVector<Instruction *> ReplacedWithConstant;
public:
FunctionSpecializer(SCCPSolver &Solver,
@@ -320,6 +321,15 @@ class FunctionSpecializer {
return Changed;
}
+ void removeDeadInstructions() {
+ for (auto *I : ReplacedWithConstant) {
+ LLVM_DEBUG(dbgs() << "FnSpecialization: Removing dead instruction "
+ << *I << "\n");
+ I->eraseFromParent();
+ }
+ ReplacedWithConstant.clear();
+ }
+
bool tryToReplaceWithConstant(Value *V) {
if (!V->getType()->isSingleValueType() || isa<CallBase>(V) ||
V->user_empty())
@@ -330,6 +340,10 @@ class FunctionSpecializer {
return false;
auto *Const =
isConstant(IV) ? Solver.getConstant(IV) : UndefValue::get(V->getType());
+
+ LLVM_DEBUG(dbgs() << "FnSpecialization: Replacing " << *V
+ << "\nFnSpecialization: with " << *Const << "\n");
+
V->replaceAllUsesWith(Const);
for (auto *U : Const->users())
@@ -340,7 +354,7 @@ class FunctionSpecializer {
// Remove the instruction from Block and Solver.
if (auto *I = dyn_cast<Instruction>(V)) {
if (I->isSafeToRemove()) {
- I->eraseFromParent();
+ ReplacedWithConstant.push_back(I);
Solver.removeLatticeValueFor(I);
}
}
@@ -886,7 +900,8 @@ bool llvm::runFunctionSpecialization(
Changed = true;
}
- // Clean up the IR by removing ssa_copy intrinsics.
+ // Clean up the IR by removing dead instructions and ssa_copy intrinsics.
+ FS.removeDeadInstructions();
removeSSACopy(M);
return Changed;
}
diff --git a/llvm/test/Transforms/FunctionSpecialization/bug52821-use-after-free.ll b/llvm/test/Transforms/FunctionSpecialization/bug52821-use-after-free.ll
new file mode 100644
index 000000000000..55af373652d0
--- /dev/null
+++ b/llvm/test/Transforms/FunctionSpecialization/bug52821-use-after-free.ll
@@ -0,0 +1,58 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -function-specialization -S < %s | FileCheck %s
+
+%mystruct = type { i32, [2 x i64] }
+
+define internal %mystruct* @myfunc(%mystruct* %arg) {
+; CHECK-LABEL: @myfunc(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[FOR_COND:%.*]]
+; CHECK: for.cond:
+; CHECK-NEXT: br i1 true, label [[FOR_COND2:%.*]], label [[FOR_BODY:%.*]]
+; CHECK: for.body:
+; CHECK-NEXT: call void @callee(%mystruct* nonnull null)
+; CHECK-NEXT: br label [[FOR_COND]]
+; CHECK: for.cond2:
+; CHECK-NEXT: br i1 false, label [[FOR_END:%.*]], label [[FOR_BODY2:%.*]]
+; CHECK: for.body2:
+; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds [[MYSTRUCT:%.*]], %mystruct* null, i64 0, i32 1, i64 3
+; CHECK-NEXT: br label [[FOR_COND2]]
+; CHECK: for.end:
+; CHECK-NEXT: ret %mystruct* [[ARG:%.*]]
+;
+entry:
+ br label %for.cond
+
+for.cond: ; preds = %for.body, %entry
+ %phi = phi %mystruct* [ undef, %for.body ], [ null, %entry ]
+ %cond = icmp eq %mystruct* %phi, null
+ br i1 %cond, label %for.cond2, label %for.body
+
+for.body: ; preds = %for.cond
+ call void @callee(%mystruct* nonnull %phi)
+ br label %for.cond
+
+for.cond2: ; preds = %for.body2, %for.cond
+ %phi2 = phi %mystruct* [ undef, %for.body2 ], [ null, %for.cond ]
+ br i1 undef, label %for.end, label %for.body2
+
+for.body2: ; preds = %for.cond2
+ %arrayidx = getelementptr inbounds %mystruct, %mystruct* %phi2, i64 0, i32 1, i64 3
+ br label %for.cond2
+
+for.end: ; preds = %for.cond2
+ ret %mystruct* %arg
+}
+
+define %mystruct* @caller() {
+; CHECK-LABEL: @caller(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CALL:%.*]] = call %mystruct* @myfunc(%mystruct* undef)
+; CHECK-NEXT: ret %mystruct* [[CALL]]
+;
+entry:
+ %call = call %mystruct* @myfunc(%mystruct* undef)
+ ret %mystruct* %call
+}
+
+declare void @callee(%mystruct*)
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