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/include/llvm/CodeGen/MachineFrameInfo.h b/include/llvm/CodeGen/MachineFrameInfo.h
index bf75578fbc30fcf3a036d084e6b4cf39c710b379..93d77287d7ca621beab9832d44775c59a6cedc22 100644 (file)
--- a/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/include/llvm/CodeGen/MachineFrameInfo.h
@@ -221,8 +221,11 @@ class MachineFrameInfo {
   /// just allocate them normally.
   bool UseLocalStackAllocationBlock;
 
+  /// Whether the "realign-stack" option is on.
+  bool RealignOption;
 public:
-    explicit MachineFrameInfo(const TargetFrameLowering &tfi) : TFI(tfi) {
+    explicit MachineFrameInfo(const TargetFrameLowering &tfi, bool RealignOpt)
+    : TFI(tfi), RealignOption(RealignOpt) {
     StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
     HasVarSizedObjects = false;
     FrameAddressTaken = false;

diff --git a/include/llvm/Target/TargetFrameLowering.h b/include/llvm/Target/TargetFrameLowering.h
index 7e54f1447e34ae5ac1a638f49d6b679139f11c65..1958f90f9b1bef7387f28c4e315e61f126ab15d7 100644 (file)
--- a/include/llvm/Target/TargetFrameLowering.h
+++ b/include/llvm/Target/TargetFrameLowering.h
@@ -47,11 +47,12 @@ private:
   unsigned StackAlignment;
   unsigned TransientStackAlignment;
   int LocalAreaOffset;
+  bool StackRealignable;
 public:
   TargetFrameLowering(StackDirection D, unsigned StackAl, int LAO,
-                      unsigned TransAl = 1)
+                      unsigned TransAl = 1, bool StackReal = true)
     : StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
-      LocalAreaOffset(LAO) {}
+      LocalAreaOffset(LAO), StackRealignable(StackReal) {}
 
   virtual ~TargetFrameLowering();
 
@@ -76,6 +77,12 @@ public:
     return TransientStackAlignment;
   }
 
+  /// isStackRealignable - This method returns whether the stack can be
+  /// realigned.
+  bool isStackRealignable() const {
+    return StackRealignable;
+  }
+
   /// getOffsetOfLocalArea - This method returns the offset of the local area
   /// from the stack pointer on entrance to a function.
   ///

diff --git a/lib/CodeGen/MachineFunction.cpp b/lib/CodeGen/MachineFunction.cpp
index f13fe14aa1b3aefa019263f03a22646c8c55b524..e88c3c16fd1eb2ad55976f3cf2398421f0559bf9 100644 (file)
--- a/lib/CodeGen/MachineFunction.cpp
+++ b/lib/CodeGen/MachineFunction.cpp
@@ -58,7 +58,8 @@ MachineFunction::MachineFunction(const Function *F, const TargetMachine &TM,
   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 @@ MCSymbol *MachineFunction::getPICBaseSymbol() const {
 /// 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::CreateStackObject(uint64_t Size, unsigned Alignment,
 ///
 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::CreateSpillStackObject(uint64_t Size,
 ///
 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 @@ int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset,
   // 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,

diff --git a/test/CodeGen/ARM/alloc-no-stack-realign.ll b/test/CodeGen/ARM/alloc-no-stack-realign.ll
new file mode 100644 (file)
index 0000000..273041d
--- /dev/null
+++ b/test/CodeGen/ARM/alloc-no-stack-realign.ll
@@ -0,0 +1,48 @@
+; RUN: llc < %s -mtriple=armv7-apple-ios -O0 -realign-stack=0 | FileCheck %s -check-prefix=NO-REALIGN
+; RUN: llc < %s -mtriple=armv7-apple-ios -O0 | FileCheck %s
+
+; rdar://12713765
+; When realign-stack is set to false, make sure we are not creating stack
+; objects that are assumed to be 64-byte aligned.
+@T3_retval = common global <16 x float> zeroinitializer, align 16
+
+define void @test(<16 x float>* noalias sret %agg.result) nounwind ssp {
+entry:
+; CHECK: test
+; CHECK: bic sp, sp, #63
+; CHECK: orr [[R2:r[0-9]+]], [[R1:r[0-9]+]], #48
+; CHECK: vst1.64
+; CHECK: orr [[R2:r[0-9]+]], [[R1:r[0-9]+]], #32
+; CHECK: vst1.64
+; CHECK: orr [[R2:r[0-9]+]], [[R1:r[0-9]+]], #16
+; CHECK: vst1.64
+; CHECK: vst1.64
+; CHECK: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #48
+; CHECK: vst1.64
+; CHECK: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #32
+; CHECK: vst1.64
+; CHECK: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #16
+; CHECK: vst1.64
+; CHECK: vst1.64
+; NO-REALIGN: test
+; NO-REALIGN: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #48
+; NO-REALIGN: vst1.64
+; NO-REALIGN: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #32
+; NO-REALIGN: vst1.64
+; NO-REALIGN: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #16
+; NO-REALIGN: vst1.64
+; NO-REALIGN: vst1.64
+; NO-REALIGN: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #48
+; NO-REALIGN: vst1.64
+; NO-REALIGN: add [[R2:r[0-9]+]], [[R1:r[0-9]+]], #32
+; NO-REALIGN: vst1.64
+; 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
+ %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
+}