From 3649b0efa5e663aba9596a0225c34f82de1d95b7 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 2 Jun 2006 22:38:37 +0000
Subject: [PATCH] Cygwin support. Patch by Anton Korobeynikov!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28672 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelDAGToDAG.cpp |  9 +++++++--
 lib/Target/X86/X86RegisterInfo.cpp | 23 +++++++++++++++++++++--
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index e8da9d79126..7f7e069b081 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -129,6 +129,8 @@ namespace {
                      SDOperand &Base, SDOperand &Scale,
                      SDOperand &Index, SDOperand &Disp);
 
+    void EmitSpecialCodeForMain(MachineBasicBlock *BB, MachineFrameInfo *MFI);
+
     inline void getAddressOperands(X86ISelAddressMode &AM, SDOperand &Base, 
                                    SDOperand &Scale, SDOperand &Index,
                                    SDOperand &Disp) {
@@ -250,8 +252,11 @@ void X86DAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
 
 /// EmitSpecialCodeForMain - Emit any code that needs to be executed only in
 /// the main function.
-static void EmitSpecialCodeForMain(MachineBasicBlock *BB,
-                                   MachineFrameInfo *MFI) {
+void X86DAGToDAGISel::EmitSpecialCodeForMain(MachineBasicBlock *BB,
+                                             MachineFrameInfo *MFI) {
+  if (Subtarget->TargetType == X86Subtarget::isCygwin)
+    BuildMI(BB, X86::CALLpcrel32, 1).addExternalSymbol("__main");
+
   // Switch the FPU to 64-bit precision mode for better compatibility and speed.
   int CWFrameIdx = MFI->CreateStackObject(2, 2);
   addFrameReference(BuildMI(BB, X86::FNSTCW16m, 4), CWFrameIdx);
diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 58180b61fff..ec4a24d503c 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -14,9 +14,12 @@
 
 #include "X86.h"
 #include "X86RegisterInfo.h"
+#include "X86Subtarget.h"
+#include "X86TargetMachine.h"
 #include "X86InstrBuilder.h"
 #include "llvm/Constants.h"
 #include "llvm/Type.h"
+#include "llvm/Function.h"
 #include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineFunction.h"
@@ -635,7 +638,14 @@ X86RegisterInfo::getCalleeSaveRegClasses() const {
 // if frame pointer elimination is disabled.
 //
 static bool hasFP(MachineFunction &MF) {
-  return NoFramePointerElim || MF.getFrameInfo()->hasVarSizedObjects();
+  const Function* Fn = MF.getFunction();
+  const X86Subtarget* Subtarget =  &MF.getTarget().getSubtarget<X86Subtarget>();
+         
+  return (NoFramePointerElim || 
+          MF.getFrameInfo()->hasVarSizedObjects() ||
+          (Fn->hasExternalLinkage() &&
+           Fn->getName() == "main" &&
+           Subtarget->TargetType == X86Subtarget::isCygwin));
 }
 
 void X86RegisterInfo::
@@ -730,6 +740,9 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
   MachineBasicBlock::iterator MBBI = MBB.begin();
   MachineFrameInfo *MFI = MF.getFrameInfo();
+  unsigned Align = MF.getTarget().getFrameInfo()->getStackAlignment();
+  const Function* Fn = MF.getFunction();
+  const X86Subtarget* Subtarget = &MF.getTarget().getSubtarget<X86Subtarget>();
   MachineInstr *MI;
 
   // Get the number of bytes to allocate from the FrameInfo
@@ -744,7 +757,6 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
 
     // Round the size to a multiple of the alignment (don't forget the 4 byte
     // offset though).
-    unsigned Align = MF.getTarget().getFrameInfo()->getStackAlignment();
     NumBytes = ((NumBytes+4)+Align-1)/Align*Align - 4;
   }
 
@@ -775,6 +787,13 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
 
     MBB.insert(MBBI, MI);
   }
+
+  // If it's main() on Cygwin\Mingw32 we should align stack as well
+  if (Fn->hasExternalLinkage() && Fn->getName() == "main" &&
+      Subtarget->TargetType == X86Subtarget::isCygwin) {
+    MI = BuildMI(X86::AND32ri, 2, X86::ESP).addImm(-Align);
+    MBB.insert(MBBI, MI);
+  }
 }
 
 void X86RegisterInfo::emitEpilogue(MachineFunction &MF,
-- 
2.11.0