Stack Alignment: when creating stack objects in MachineFrameInfo, make sure
the alignment is clamped to TargetFrameLowering.getStackAlignment if the target
does not support stack realignment or the option "realign-stack" is off.
This will cause miscompile if the address is treated as aligned and add is
replaced with or in DAGCombine.
Added a bool StackRealignable to TargetFrameLowering to check whether stack
realignment is implemented for the target. Also added a bool RealignOption
to MachineFrameInfo to check whether the option "realign-stack" is on.
rdar://12713765
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169197 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineFunction.cpp b/lib/CodeGen/MachineFunction.cpp
index f13fe14..e88c3c1 100644
--- a/lib/CodeGen/MachineFunction.cpp
+++ b/lib/CodeGen/MachineFunction.cpp
@@ -58,7 +58,8 @@
else
RegInfo = 0;
MFInfo = 0;
- FrameInfo = new (Allocator) MachineFrameInfo(*TM.getFrameLowering());
+ FrameInfo = new (Allocator) MachineFrameInfo(*TM.getFrameLowering(),
+ TM.Options.RealignStack);
if (Fn->getFnAttributes().hasAttribute(Attributes::StackAlignment))
FrameInfo->ensureMaxAlignment(Fn->getAttributes().
getFnAttributes().getStackAlignment());
@@ -448,15 +449,31 @@
/// ensureMaxAlignment - Make sure the function is at least Align bytes
/// aligned.
void MachineFrameInfo::ensureMaxAlignment(unsigned Align) {
+ if (!TFI.isStackRealignable() || !RealignOption)
+ assert(Align <= TFI.getStackAlignment() &&
+ "For targets without stack realignment, Align is out of limit!");
if (MaxAlignment < Align) MaxAlignment = 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');
+ return StackAlign;
+}
+
/// CreateStackObject - Create a new statically sized stack object, returning
/// a nonnegative identifier to represent it.
///
int MachineFrameInfo::CreateStackObject(uint64_t Size, unsigned Alignment,
bool isSS, bool MayNeedSP, const AllocaInst *Alloca) {
assert(Size != 0 && "Cannot allocate zero size stack objects!");
+ Alignment = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
+ Alignment, TFI.getStackAlignment());
Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP,
Alloca));
int Index = (int)Objects.size() - NumFixedObjects - 1;
@@ -471,6 +488,8 @@
///
int MachineFrameInfo::CreateSpillStackObject(uint64_t Size,
unsigned Alignment) {
+ Alignment = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
+ Alignment, TFI.getStackAlignment());
CreateStackObject(Size, Alignment, true, false);
int Index = (int)Objects.size() - NumFixedObjects - 1;
ensureMaxAlignment(Alignment);
@@ -484,6 +503,8 @@
///
int MachineFrameInfo::CreateVariableSizedObject(unsigned Alignment) {
HasVarSizedObjects = true;
+ Alignment = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
+ Alignment, TFI.getStackAlignment());
Objects.push_back(StackObject(0, Alignment, 0, false, false, true, 0));
ensureMaxAlignment(Alignment);
return (int)Objects.size()-NumFixedObjects-1;
@@ -503,6 +524,8 @@
// object is 16-byte aligned.
unsigned StackAlign = TFI.getStackAlignment();
unsigned Align = MinAlign(SPOffset, StackAlign);
+ Align = clampStackAlignment(!TFI.isStackRealignable() || !RealignOption,
+ Align, TFI.getStackAlignment());
Objects.insert(Objects.begin(), StackObject(Size, Align, SPOffset, Immutable,
/*isSS*/ false,
/*NeedSP*/ false,