commit e9b2eed90ebc564917e62f79a5da0a72c394aadf
author Jim Grosbach <grosbach@apple.com> Tue Jan 19 18:31:11 2010 +0000
committer Jim Grosbach <grosbach@apple.com> Tue Jan 19 18:31:11 2010 +0000
tree c2cb2db266d2fc51246754d560fdf5b1ba792e8d
parent 0c4f848e4148c2bf86565f6f7612e0305c17cbb9

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.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93885 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86InstrInfo.cpp

diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 7b39fb3..8b9d0b8 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -2077,8 +2077,7 @@
                                        unsigned SrcReg, bool isKill, int FrameIdx,
                                        const TargetRegisterClass *RC) const {
   const MachineFunction &MF = *MBB.getParent();
-  bool isAligned = (RI.getStackAlignment() >= 16) ||
-    RI.needsStackRealignment(MF);
+  bool isAligned = (RI.getStackAlignment() >= 16) || RI.canRealignStack(MF);
   unsigned Opc = getStoreRegOpcode(SrcReg, RC, isAligned, TM);
   DebugLoc DL = DebugLoc::getUnknownLoc();
   if (MI != MBB.end()) DL = MI->getDebugLoc();
@@ -2172,8 +2171,7 @@
                                         unsigned DestReg, int FrameIdx,
                                         const TargetRegisterClass *RC) const{
   const MachineFunction &MF = *MBB.getParent();
-  bool isAligned = (RI.getStackAlignment() >= 16) ||
-    RI.needsStackRealignment(MF);
+  bool isAligned = (RI.getStackAlignment() >= 16) || RI.canRealignStack(MF);
   unsigned Opc = getLoadRegOpcode(DestReg, RC, isAligned, TM);
   DebugLoc DL = DebugLoc::getUnknownLoc();
   if (MI != MBB.end()) DL = MI->getDebugLoc();

lib/Target/X86/X86RegisterInfo.cpp

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index d96aafd..4bc2c9e 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -438,6 +438,12 @@
           (MMI && MMI->callsUnwindInit()));
 }
 
+bool X86RegisterInfo::canRealignStack(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  return (RealignStack &&
+          !MFI->hasVarSizedObjects());
+}
+
 bool X86RegisterInfo::needsStackRealignment(const MachineFunction &MF) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   bool requiresRealignment =

lib/Target/X86/X86RegisterInfo.h

diff --git a/lib/Target/X86/X86RegisterInfo.h b/lib/Target/X86/X86RegisterInfo.h
index f281a3c..dec3fba 100644
--- a/lib/Target/X86/X86RegisterInfo.h
+++ b/lib/Target/X86/X86RegisterInfo.h
@@ -128,6 +128,8 @@
 
   bool hasFP(const MachineFunction &MF) const;
 
+  bool canRealignStack(const MachineFunction &MF) const;
+
   bool needsStackRealignment(const MachineFunction &MF) const;
 
   bool hasReservedCallFrame(MachineFunction &MF) const;

lib/Target/X86/X86TargetMachine.cpp

diff --git a/lib/Target/X86/X86TargetMachine.cpp b/lib/Target/X86/X86TargetMachine.cpp
index 445318e..731c3ab 100644
--- a/lib/Target/X86/X86TargetMachine.cpp
+++ b/lib/Target/X86/X86TargetMachine.cpp
@@ -157,9 +157,6 @@
 
 bool X86TargetMachine::addPreRegAlloc(PassManagerBase &PM,
                                       CodeGenOpt::Level OptLevel) {
-  // Calculate and set max stack object alignment early, so we can decide
-  // whether we will need stack realignment (and thus FP).
-  PM.add(createMaxStackAlignmentCalculatorPass());
   return false;  // -print-machineinstr shouldn't print after this.
 }