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Stack Alignment: throw error if we can't satisfy the minimal alignment

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requirement when creating stack objects in MachineFrameInfo.

Add CreateStackObjectWithMinAlign to throw error when the minimal alignment
can't be achieved and to clamp the alignment when the preferred alignment
can't be achieved. Same is true for CreateVariableSizedObject.
Will not emit error in CreateSpillStackObject or CreateStackObject.

As long as callers of CreateStackObject do not assume the object will be
aligned at the requested alignment, we should not have miscompile since
later optimizations which look at the object's alignment will have the correct
information.

rdar://12713765


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172027 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren 2013-01-10 01:10:10 +00:00
parent 7932c41884
commit 86441169da
6 changed files with 70 additions and 24 deletions
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19
include/llvm/CodeGen/MachineFrameInfo.h
View File

@ -493,11 +493,23 @@ public:
return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
}
/// CreateStackObjectWithMinAlign - Create a new statically sized stack
/// object, returning a nonnegative identifier to represent it. This function
/// takes a preferred alignment and a minimal alignment.
///
int CreateStackObjectWithMinAlign(uint64_t Size, unsigned PrefAlignment,
unsigned MinAlignment, bool isSS,
bool MayNeedSP = false, const AllocaInst *Alloca = 0);
/// CreateStackObject - Create a new statically sized stack object, returning
/// a nonnegative identifier to represent it.
/// a nonnegative identifier to represent it. Will not emit an error when
/// Alignment can't be satisfied.
///
int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
bool MayNeedSP = false, const AllocaInst *Alloca = 0);
bool MayNeedSP = false, const AllocaInst *Alloca = 0) {
return CreateStackObjectWithMinAlign(Size, Alignment, 0, isSS,
MayNeedSP, Alloca);
}
/// CreateSpillStackObject - Create a new statically sized stack object that
/// represents a spill slot, returning a nonnegative identifier to represent
@ -517,7 +529,8 @@ public:
/// variable sized object is created, whether or not the index returned is
/// actually used.
///
int CreateVariableSizedObject(unsigned Alignment);
int CreateVariableSizedObject(unsigned PrefAlignment, unsigned MinAlignment,
const AllocaInst *Alloca = 0);
/// getCalleeSavedInfo - Returns a reference to call saved info vector for the
/// current function.

46
lib/CodeGen/MachineFunction.cpp
View File

@ -473,24 +473,32 @@ void MachineFrameInfo::ensureMaxAlignment(unsigned Align) {
}
/// clampStackAlignment - Clamp the alignment if requested and emit a warning.
static inline unsigned clampStackAlignment(bool ShouldClamp, unsigned Align,
unsigned StackAlign) {
if (!ShouldClamp || Align <= StackAlign)
return Align;
DEBUG(dbgs() << "Warning: requested alignment " << Align
<< " exceeds the stack alignment " << StackAlign
<< " when stack realignment is off" << '\n');
static inline unsigned clampStackAlignment(bool ShouldClamp, unsigned PrefAlign,
unsigned MinAlign, unsigned StackAlign,
const AllocaInst *Alloca = 0) {
if (!ShouldClamp || PrefAlign <= StackAlign)
return PrefAlign;
if (Alloca && MinAlign > StackAlign)
Alloca->getParent()->getContext().emitError(Alloca,
"Requested Minimal Alignment exceeds the Stack Alignment!");
else
assert(MinAlign <= StackAlign &&
"Requested Minimal Alignment exceeds the Stack Alignment!");
return StackAlign;
}
/// CreateStackObject - Create a new statically sized stack object, returning
/// a nonnegative identifier to represent it.
/// CreateStackObjectWithMinAlign - Create a new statically sized stack
/// object, returning a nonnegative identifier to represent it. This function
/// takes a preferred alignment and a minimal alignment.
///
int MachineFrameInfo::CreateStackObject(uint64_t Size, unsigned Alignment,
int MachineFrameInfo::CreateStackObjectWithMinAlign(uint64_t Size,
unsigned PrefAlignment, unsigned MinAlignment,
bool isSS, bool MayNeedSP, const AllocaInst *Alloca) {
assert(Size != 0 && "Cannot allocate zero size stack objects!");
Alignment = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
Alignment, TFI.getStackAlignment());
unsigned Alignment = clampStackAlignment(
!TFI.isStackRealignable() || !RealignOption,
PrefAlignment, MinAlignment,
TFI.getStackAlignment(), Alloca);
Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP,
Alloca));
int Index = (int)Objects.size() - NumFixedObjects - 1;
@ -506,7 +514,8 @@ int MachineFrameInfo::CreateStackObject(uint64_t Size, unsigned Alignment,
int MachineFrameInfo::CreateSpillStackObject(uint64_t Size,
unsigned Alignment) {
Alignment = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
Alignment, TFI.getStackAlignment());
Alignment, 0,
TFI.getStackAlignment());
CreateStackObject(Size, Alignment, true, false);
int Index = (int)Objects.size() - NumFixedObjects - 1;
ensureMaxAlignment(Alignment);
@ -518,10 +527,13 @@ int MachineFrameInfo::CreateSpillStackObject(uint64_t Size,
/// variable sized object is created, whether or not the index returned is
/// actually used.
///
int MachineFrameInfo::CreateVariableSizedObject(unsigned Alignment) {
int MachineFrameInfo::CreateVariableSizedObject(unsigned PrefAlignment,
unsigned MinAlignment, const AllocaInst *Alloca) {
HasVarSizedObjects = true;
Alignment = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
Alignment, TFI.getStackAlignment());
unsigned Alignment = clampStackAlignment(
!TFI.isStackRealignable() || !RealignOption,
PrefAlignment, MinAlignment,
TFI.getStackAlignment(), Alloca);
Objects.push_back(StackObject(0, Alignment, 0, false, false, true, 0));
ensureMaxAlignment(Alignment);
return (int)Objects.size()-NumFixedObjects-1;
@ -542,7 +554,7 @@ int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset,
unsigned StackAlign = TFI.getStackAlignment();
unsigned Align = MinAlign(SPOffset, StackAlign);
Align = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
Align, TFI.getStackAlignment());
Align, 0, TFI.getStackAlignment());
Objects.insert(Objects.begin(), StackObject(Size, Align, SPOffset, Immutable,
/*isSS*/ false,
/*NeedSP*/ false,

3
lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
View File

@ -95,7 +95,8 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
(TySize >= 8 && isa<ArrayType>(Ty) &&
cast<ArrayType>(Ty)->getElementType()->isIntegerTy(8)));
StaticAllocaMap[AI] =
MF->getFrameInfo()->CreateStackObject(TySize, Align, false,
MF->getFrameInfo()->CreateStackObjectWithMinAlign(TySize, Align,
AI->getAlignment(), false,
MayNeedSP, AI);
}

3
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
View File

@ -3259,7 +3259,8 @@ void SelectionDAGBuilder::visitAlloca(const AllocaInst &I) {
// Inform the Frame Information that we have just allocated a variable-sized
// object.
FuncInfo.MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1);
FuncInfo.MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1,
I.getAlignment(), &I);
}
void SelectionDAGBuilder::visitLoad(const LoadInst &I) {

19
test/CodeGen/ARM/alloc-no-stack-realign-error.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: llc < %s -mtriple=armv7-apple-ios -O0 -realign-stack=0 2>&1 | FileCheck %s
; rdar://12713765
@T3_retval = common global <16 x float> zeroinitializer, align 16
; If alignment for alloc is smaller than or equal to stack alignment, but the
; preferred type alignment is bigger, the alignment will be clamped.
; If alignment for alloca is bigger than stack alignment, the compiler
; will emit an error.
define void @test(<16 x float>* noalias sret %agg.result) nounwind ssp {
entry:
; CHECK: Requested Minimal Alignment exceeds the Stack Alignment!
%retval = alloca <16 x float>, align 16
%0 = load <16 x float>* @T3_retval, align 16
store <16 x float> %0, <16 x float>* %retval
%1 = load <16 x float>* %retval
store <16 x float> %1, <16 x float>* %agg.result, align 16
ret void
}

2
test/CodeGen/ARM/alloc-no-stack-realign.ll
View File

@ -39,7 +39,7 @@ entry:
; NO-REALIGN: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #16
; NO-REALIGN: vst1.64
; NO-REALIGN: vst1.64
%retval = alloca <16 x float>, align 16
%retval = alloca <16 x float>, align 4
%0 = load <16 x float>* @T3_retval, align 16
store <16 x float> %0, <16 x float>* %retval
%1 = load <16 x float>* %retval