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Reland r262337 "calculate builtin_object_size if arg is a removable pointer"

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Original commit message:
 calculate builtin_object_size if argument is a removable pointer

 This patch fixes calculating correct value for builtin_object_size function
 when pointer is used only in builtin_object_size function call and never
 after that.

 Patch by Strahinja Petrovic.

 Differential Revision: http://reviews.llvm.org/D17337

Reland the original change with a small modification (first do a null check
and then do the cast) to satisfy ubsan.

llvm-svn: 263011
This commit is contained in:
Petar Jovanovic 2016-03-09 14:12:47 +00:00
parent 14e90de755
commit d649b976d0
2 changed files with 59 additions and 8 deletions
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33
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -1942,8 +1942,31 @@ Instruction *InstCombiner::visitAllocSite(Instruction &MI) {
SmallVector<WeakVH, 64> Users;
if (isAllocSiteRemovable(&MI, Users, TLI)) {
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
Instruction *I = cast_or_null<Instruction>(&*Users[i]);
if (!I) continue;
// 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)) {
if (II->getIntrinsicID() == Intrinsic::objectsize) {
uint64_t Size;
if (!getObjectSize(II->getArgOperand(0), Size, DL, TLI)) {
ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1));
Size = CI->isZero() ? -1ULL : 0;
}
replaceInstUsesWith(*I, ConstantInt::get(I->getType(), Size));
eraseInstFromFunction(*I);
Users[i] = nullptr; // Skip examining in the next loop.
}
}
}
for (unsigned i = 0, e = Users.size(); i != e; ++i) {
if (!Users[i])
continue;
Instruction *I = cast<Instruction>(&*Users[i]);
if (ICmpInst *C = dyn_cast<ICmpInst>(I)) {
replaceInstUsesWith(*C,
@ -1951,12 +1974,6 @@ Instruction *InstCombiner::visitAllocSite(Instruction &MI) {
C->isFalseWhenEqual()));
} else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
replaceInstUsesWith(*I, UndefValue::get(I->getType()));
} else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
if (II->getIntrinsicID() == Intrinsic::objectsize) {
ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1));
uint64_t DontKnow = CI->isZero() ? -1ULL : 0;
replaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow));
}
}
eraseInstFromFunction(*I);
}

34
test/Transforms/InstCombine/builtin-object-size-ptr.ll Normal file
View File

@ -0,0 +1,34 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; int foo() {
; struct V { char buf1[10];
; int b;
; char buf2[10];
; } var;
;
; char *p = &var.buf1[1];
; return __builtin_object_size (p, 0);
; }
%struct.V = type { [10 x i8], i32, [10 x i8] }
define i32 @foo() #0 {
entry:
%var = alloca %struct.V, align 4
%0 = bitcast %struct.V* %var to i8*
call void @llvm.lifetime.start(i64 28, i8* %0) #3
%buf1 = getelementptr inbounds %struct.V, %struct.V* %var, i32 0, i32 0
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buf1, i64 0, i64 1
%1 = call i64 @llvm.objectsize.i64.p0i8(i8* %arrayidx, i1 false)
%conv = trunc i64 %1 to i32
call void @llvm.lifetime.end(i64 28, i8* %0) #3
ret i32 %conv
; CHECK: ret i32 27
; CHECK-NOT: ret i32 -1
}
declare void @llvm.lifetime.start(i64, i8* nocapture) #1
declare i64 @llvm.objectsize.i64.p0i8(i8*, i1) #2
declare void @llvm.lifetime.end(i64, i8* nocapture) #1