From 4ad174b23607f5975fb0b8e14090c044a22f6d1a Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Tue, 27 Jan 2009 00:40:06 +0000
Subject: [PATCH] Fix the Red Zone calculation for functions with frame
 pointers.

Don't use the Red Zone when dynamic stack realignment is needed.
This could be implemented, but most x86-64 ABIs don't require
dynamic stack realignment so it isn't urgent.

llvm-svn: 63074
---
 lib/Target/X86/X86RegisterInfo.cpp | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 08746f2ffb4..73cab622b66 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -721,24 +721,27 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
   // Get desired stack alignment
   uint64_t MaxAlign  = MFI->getMaxAlignment();
 
-  // If this is x86-64 and the Red Zone is not disabled, if we are a leaf
-  // function, and use up to 128 bytes of stack space, don't have a frame
-  // pointer, calls, or dynamic alloca then we do not need to adjust the
-  // stack pointer (we fit in the Red Zone).
-  if (Is64Bit && !DisableRedZone &&
-      !MFI->hasVarSizedObjects() &&                // No dynamic alloca.
-      !MFI->hasCalls()) {                          // No calls.
-    StackSize = std::max((uint64_t)X86FI->getCalleeSavedFrameSize(),
-                         StackSize > 128 ? StackSize - 128 : 0);
-    MFI->setStackSize(StackSize);
-  }
-
   // Add RETADDR move area to callee saved frame size.
   int TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
   if (TailCallReturnAddrDelta < 0)
     X86FI->setCalleeSavedFrameSize(
           X86FI->getCalleeSavedFrameSize() +(-TailCallReturnAddrDelta));
 
+  // If this is x86-64 and the Red Zone is not disabled, if we are a leaf
+  // function, and use up to 128 bytes of stack space, don't have a frame
+  // pointer, calls, or dynamic alloca then we do not need to adjust the
+  // stack pointer (we fit in the Red Zone).
+  if (Is64Bit && !DisableRedZone &&
+      !needsStackRealignment(MF) &&
+      !MFI->hasVarSizedObjects() &&                // No dynamic alloca.
+      !MFI->hasCalls()) {                          // No calls.
+    uint64_t MinSize = X86FI->getCalleeSavedFrameSize();
+    if (hasFP(MF)) MinSize += SlotSize;
+    StackSize = std::max(MinSize,
+                         StackSize > 128 ? StackSize - 128 : 0);
+    MFI->setStackSize(StackSize);
+  }
+
   // Insert stack pointer adjustment for later moving of return addr.  Only
   // applies to tail call optimized functions where the callee argument stack
   // size is bigger than the callers.