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[InstCombine] avoid crash from deleting an instruction that still has uses (PR43723) 

We gather a set of white-listed instructions in isAllocSiteRemovable() and then
replace/erase them. But we don't know in general if the instructions in the set
have uses amongst themselves, so order of deletion makes a difference.

There's already a special-case for the llvm.objectsize intrinsic, so add another
for llvm.invariant.end.

Should fix:
https://bugs.llvm.org/show_bug.cgi?id=43723

Differential Revision: https://reviews.llvm.org/D69977
This commit is contained in:
Sanjay Patel 2019-11-10 09:16:32 -05:00
parent 4ff246fef2
commit ef02831f0a
2 changed files with 52 additions and 4 deletions
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21
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -2330,13 +2330,21 @@ static bool isAllocSiteRemovable(Instruction *AI,
return false;
LLVM_FALLTHROUGH;
}
case Intrinsic::invariant_start:
case Intrinsic::invariant_end:
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
case Intrinsic::objectsize:
Users.emplace_back(I);
continue;
case Intrinsic::invariant_start:
// Only delete this if it has no uses or a single 'end' use.
if (I->use_empty())
Users.emplace_back(I);
else if (I->hasOneUse() &&
match(I->user_back(),
m_Intrinsic<Intrinsic::invariant_end>()))
Users.emplace_back(I);
continue;
}
}
@ -2384,14 +2392,13 @@ Instruction *InstCombiner::visitAllocSite(Instruction &MI) {
if (isAllocSiteRemovable(&MI, Users, &TLI)) {
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
// Lowering all @llvm.objectsize calls first because they may
// use a bitcast/GEP of the alloca we are removing.
if (!Users[i])
continue;
Instruction *I = cast<Instruction>(&*Users[i]);
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
// Lowering all @llvm.objectsize calls first because they may
// use a bitcast/GEP of the alloca we are removing.
if (II->getIntrinsicID() == Intrinsic::objectsize) {
Value *Result =
lowerObjectSizeCall(II, DL, &TLI, /*MustSucceed=*/true);
@ -2399,6 +2406,12 @@ Instruction *InstCombiner::visitAllocSite(Instruction &MI) {
eraseInstFromFunction(*I);
Users[i] = nullptr; // Skip examining in the next loop.
}
// Erase llvm.invariant.end because we expect that it uses an
// llvm.invariant.start that we will remove below.
if (II->getIntrinsicID() == Intrinsic::invariant_end) {
eraseInstFromFunction(*I);
Users[i] = nullptr; // Skip examining in the next loop.
}
}
}
for (unsigned i = 0, e = Users.size(); i != e; ++i) {

35
llvm/test/Transforms/InstCombine/builtin-object-size-ptr.ll
View File

@ -28,6 +28,41 @@ define i32 @foo() #0 {
ret i32 %conv
}
; This used to crash while erasing instructions:
; https://bugs.llvm.org/show_bug.cgi?id=43723
define void @PR43723() {
; CHECK-LABEL: @PR43723(
; CHECK-NEXT: ret void
;
%tab = alloca [10 x i8], align 16
%t0 = bitcast [10 x i8]* %tab to i8*
call void @llvm.memset.p0i8.i64(i8* align 16 %t0, i8 9, i64 10, i1 false)
%t1 = call {}* @llvm.invariant.start.p0i8(i64 10, i8* align 16 %t0)
call void @llvm.invariant.end.p0i8({}* %t1, i64 10, i8* align 16 %t0)
ret void
uselistorder i8* %t0, { 1, 0, 2 }
}
define void @unknown_use_of_invariant_start({}** %p) {
; CHECK-LABEL: @unknown_use_of_invariant_start(
; CHECK-NEXT: [[T1:%.*]] = call {}* @llvm.invariant.start.p0i8(i64 10, i8* align 16 undef)
; CHECK-NEXT: store {}* [[T1]], {}** [[P:%.*]], align 8
; CHECK-NEXT: ret void
;
%tab = alloca [10 x i8], align 16
%t0 = bitcast [10 x i8]* %tab to i8*
call void @llvm.memset.p0i8.i64(i8* align 16 %t0, i8 9, i64 10, i1 false)
%t1 = call {}* @llvm.invariant.start.p0i8(i64 10, i8* align 16 %t0)
call void @llvm.invariant.end.p0i8({}* %t1, i64 10, i8* align 16 %t0)
store {}* %t1, {}** %p
ret void
}
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
declare i64 @llvm.objectsize.i64.p0i8(i8*, i1) #2
declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture) #1
declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg) #0
declare {}* @llvm.invariant.start.p0i8(i64 immarg, i8* nocapture) #0
declare void @llvm.invariant.end.p0i8({}*, i64 immarg, i8* nocapture) #0