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Minor refactoring of GEP handling in isDereferenceablePointer

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For GEP instructions isDereferenceablePointer checks that all indices are constant and within bounds. Replace this index calculation logic to a call to accumulateConstantOffset. Separated from the http://reviews.llvm.org/D9791

Reviewed By: sanjoy

Differential Revision: http://reviews.llvm.org/D9874

llvm-svn: 239299
This commit is contained in:
Artur Pilipenko 2015-06-08 11:58:13 +00:00
parent e570ae0867
commit c17a17c081
2 changed files with 28 additions and 28 deletions
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43
lib/Analysis/ValueTracking.cpp
View File

@ -2967,38 +2967,25 @@ static bool isDereferenceablePointer(const Value *V, const DataLayout &DL,
// For GEPs, determine if the indexing lands within the allocated object.
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
Type *VTy = GEP->getType();
Type *Ty = VTy->getPointerElementType();
const Value *Base = GEP->getPointerOperand();
// Conservatively require that the base pointer be fully dereferenceable.
if (!Visited.insert(GEP->getOperand(0)).second)
if (!Visited.insert(Base).second)
return false;
if (!isDereferenceablePointer(GEP->getOperand(0), DL, CtxI,
if (!isDereferenceablePointer(Base, DL, CtxI,
DT, TLI, Visited))
return false;
// Check the indices.
gep_type_iterator GTI = gep_type_begin(GEP);
for (User::const_op_iterator I = GEP->op_begin()+1,
E = GEP->op_end(); I != E; ++I) {
Value *Index = *I;
Type *Ty = *GTI++;
// Struct indices can't be out of bounds.
if (isa<StructType>(Ty))
continue;
ConstantInt *CI = dyn_cast<ConstantInt>(Index);
if (!CI)
return false;
// Zero is always ok.
if (CI->isZero())
continue;
// Check to see that it's within the bounds of an array.
ArrayType *ATy = dyn_cast<ArrayType>(Ty);
if (!ATy)
return false;
if (CI->getValue().getActiveBits() > 64)
return false;
if (CI->getZExtValue() >= ATy->getNumElements())
return false;
}
// Indices check out; this is dereferenceable.
return true;
APInt Offset(DL.getPointerTypeSizeInBits(VTy), 0);
if (!GEP->accumulateConstantOffset(DL, Offset))
return false;
// Check if the load is within the bounds of the underlying object.
uint64_t LoadSize = DL.getTypeStoreSize(Ty);
Type *BaseType = Base->getType()->getPointerElementType();
return (Offset + LoadSize).ule(DL.getTypeAllocSize(BaseType));
}
// For gc.relocate, look through relocations

13
test/Analysis/ValueTracking/memory-dereferenceable.ll
View File

@ -10,6 +10,9 @@ declare zeroext i1 @return_i1()
@globalstr = global [6 x i8] c"hello\00"
@globali32ptr = external global i32*
%struct.A = type { [8 x i8], [5 x i8] }
@globalstruct = external global %struct.A
define void @test(i32 addrspace(1)* dereferenceable(8) %dparam) gc "statepoint-example" {
; CHECK: The following are dereferenceable:
; CHECK: %globalptr
@ -22,6 +25,8 @@ define void @test(i32 addrspace(1)* dereferenceable(8) %dparam) gc "statepoint-e
; CHECK-NOT: %d2_load
; CHECK-NOT: %d_or_null_load
; CHECK: %d_or_null_non_null_load
; CHECK: %within_allocation
; CHECK-NOT: %outside_allocation
entry:
%globalptr = getelementptr inbounds [6 x i8], [6 x i8]* @globalstr, i32 0, i32 0
%load1 = load i8, i8* %globalptr
@ -54,6 +59,14 @@ entry:
%d_or_null_non_null_load = load i32*, i32** @globali32ptr, !nonnull !2, !dereferenceable_or_null !0
%load10 = load i32, i32* %d_or_null_non_null_load
; It's OK to overrun static array size as long as we stay within underlying object size
%within_allocation = getelementptr inbounds %struct.A, %struct.A* @globalstruct, i64 0, i32 0, i64 10
%load11 = load i8, i8* %within_allocation
; GEP is outside the underlying object size
%outside_allocation = getelementptr inbounds %struct.A, %struct.A* @globalstruct, i64 0, i32 1, i64 10
%load12 = load i8, i8* %outside_allocation
ret void
}