Eastimate required stack alignment early, so we can decide, whether we will need frame pointer or not

llvm-svn: 50161

2 files changed, 21 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 46bf76f7578..2baf3601f01 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -372,6 +372,25 @@ void X86RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
 }
 
 void
+X86RegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
+                                                      RegScavenger *RS) const {
+  MachineFrameInfo *FFI = MF.getFrameInfo();
+
+  // Calculate and set max stack object alignment early, so we can decide
+  // whether we will need stack realignment (and thus FP).
+  unsigned MaxAlign = 0;
+  for (int i = FFI->getObjectIndexBegin(),
+         e = FFI->getObjectIndexEnd(); i != e; ++i) {
+    if (FFI->isDeadObjectIndex(i))
+      continue;
+    unsigned Align = FFI->getObjectAlignment(i);
+    MaxAlign = std::max(MaxAlign, Align);
+  }
+
+  FFI->setMaxAlignment(MaxAlign);
+}
+
+void
 X86RegisterInfo::processFunctionBeforeFrameFinalized(MachineFunction &MF) const{
   X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
   int32_t TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.h b/llvm/lib/Target/X86/X86RegisterInfo.h
index fdf74b11f56..40fdfb00e3e 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.h
+++ b/llvm/lib/Target/X86/X86RegisterInfo.h
@@ -127,6 +127,8 @@ public:
                            int SPAdj, RegScavenger *RS = NULL) const;
 
   void processFunctionBeforeFrameFinalized(MachineFunction &MF) const;
+  void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
+                                            RegScavenger *RS = NULL) const;
 
   void emitPrologue(MachineFunction &MF) const;
   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const;