For aligned load/store instructions, it's only required to know whether a

function can support dynamic stack realignment. That's a much easier question
to answer at instruction selection stage than whether the function actually
will have dynamic alignment prologue. This allows the removal of the
stack alignment heuristic pass, and improves code quality for cases where
the heuristic would result in dynamic alignment code being generated when
it was not strictly necessary.

llvm-svn: 93885

4 files changed, 11 insertions, 6 deletions

diff --git a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 969c4a4c861..fd46a4a8c54 100644
--- a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -715,7 +715,7 @@ storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
             RC == ARM::QPR_VFP2RegisterClass) && "Unknown regclass!");
     // FIXME: Neon instructions should support predicates
     if (Align >= 16
-        && (getRegisterInfo().needsStackRealignment(MF))) {
+        && (getRegisterInfo().canRealignStack(MF))) {
       AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::VST1q64))
                      .addFrameIndex(FI).addImm(0).addImm(0).addImm(128)
                      .addMemOperand(MMO)
@@ -760,7 +760,7 @@ loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
             RC == ARM::QPR_VFP2RegisterClass ||
             RC == ARM::QPR_8RegisterClass) && "Unknown regclass!");
     if (Align >= 16
-        && (getRegisterInfo().needsStackRealignment(MF))) {
+        && (getRegisterInfo().canRealignStack(MF))) {
       AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::VLD1q64), DestReg)
                      .addFrameIndex(FI).addImm(0).addImm(0).addImm(128)
                      .addMemOperand(MMO));
diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index f1b6e1d8c57..ba9e044afc3 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -484,6 +484,14 @@ bool ARMBaseRegisterInfo::hasFP(const MachineFunction &MF) const {
           MFI->isFrameAddressTaken());
 }
 
+bool ARMBaseRegisterInfo::canRealignStack(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
+  return (RealignStack &&
+          !AFI->isThumb1OnlyFunction() &&
+          !MFI->hasVarSizedObjects());
+}
+
 bool ARMBaseRegisterInfo::
 needsStackRealignment(const MachineFunction &MF) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
index 2788d0733d1..f5ca25c1e30 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
@@ -96,6 +96,7 @@ public:
 
   bool hasFP(const MachineFunction &MF) const;
 
+  bool canRealignStack(const MachineFunction &MF) const;
   bool needsStackRealignment(const MachineFunction &MF) const;
 
   bool cannotEliminateFrame(const MachineFunction &MF) const;
diff --git a/llvm/lib/Target/ARM/ARMTargetMachine.cpp b/llvm/lib/Target/ARM/ARMTargetMachine.cpp
index 1c6fca7decc..4d20a5c1a03 100644
--- a/llvm/lib/Target/ARM/ARMTargetMachine.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetMachine.cpp
@@ -93,10 +93,6 @@ bool ARMBaseTargetMachine::addPreRegAlloc(PassManagerBase &PM,
   if (Subtarget.hasNEON())
     PM.add(createNEONPreAllocPass());
 
-  // Calculate and set max stack object alignment early, so we can decide
-  // whether we will need stack realignment (and thus FP).
-  PM.add(createMaxStackAlignmentCalculatorPass());
-
   // FIXME: temporarily disabling load / store optimization pass for Thumb1.
   if (OptLevel != CodeGenOpt::None && !Subtarget.isThumb1Only())
     PM.add(createARMLoadStoreOptimizationPass(true));