[llvm-commits] [llvm] r113366 - /llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp

[Jim Grosbach]

Author: grosbach
Date: Wed Sep  8 12:22:12 2010
New Revision: 113366

URL: http://llvm.org/viewvc/llvm-project?rev=113366&view=rev
Log:
Be more careful about when to do dynamic stack realignment. Since we have an
option to disable base pointer usage, pay attention to it when deciding
if we can realign (if no base pointer and VLAs, we can't).

Modified:
    llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp

Modified: llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp?rev=113366&r1=113365&r2=113366&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp Wed Sep  8 12:22:12 2010
@@ -667,8 +667,14 @@
 }
 
 bool ARMBaseRegisterInfo::canRealignStack(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
   const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
-  return (RealignStack && !AFI->isThumb1OnlyFunction());
+  // We can't realign the stack if:
+  // 1. Dynamic stack realignment is explicitly disabled,
+  // 2. This is a Thumb1 function (it's not useful, so we don't bother), or
+  // 3. There are VLAs in the function and the base pointer is disabled.
+  return (RealignStack && !AFI->isThumb1OnlyFunction() &&
+          (!MFI->hasVarSizedObjects() || EnableBasePointer));
 }
 
 bool ARMBaseRegisterInfo::
@@ -1890,7 +1896,8 @@
   AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
   AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
 
-  // If we need dynamic stack realignment, do it here.
+  // If we need dynamic stack realignment, do it here. Be paranoid and make
+  // sure if we also have VLAs, we have a base pointer for frame access.
   if (needsStackRealignment(MF)) {
     unsigned MaxAlign = MFI->getMaxAlignment();
     assert (!AFI->isThumb1OnlyFunction());