* Add special entry code main() (to set x87 to 64-bit precision).

* Allow a register node as SelectAddr() base.
* ExternalSymbol -> TargetExternalSymbol as direct function callee.
* Use X86::ESP register rather than CopyFromReg(X86::ESP) as stack ptr for
  call parmater passing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25207 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86ISelDAGToDAG.cpp

@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "X86.h"
+#include "X86InstrBuilder.h"
 #include "X86RegisterInfo.h"
 #include "X86Subtarget.h"
 #include "X86ISelLowering.h"
@@ -95,6 +96,8 @@ namespace {
     /// SelectionDAGISel when it has created a SelectionDAG for us to codegen.
     virtual void InstructionSelectBasicBlock(SelectionDAG &DAG);
 
+    virtual void EmitFunctionEntryCode(Function &Fn, MachineFunction &MF);
+
 // Include the pieces autogenerated from the target description.
 #include "X86GenDAGISel.inc"
 
@@ -208,7 +211,29 @@ void X86DAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
   }
 }
 
-/// FIXME: copied from X86ISelPattern.cpp
+/// EmitSpecialCodeForMain - Emit any code that needs to be executed only in
+/// the main function.
+static void EmitSpecialCodeForMain(MachineBasicBlock *BB,
+                                   MachineFrameInfo *MFI) {
+  // 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);
+
+  // Set the high part to be 64-bit precision.
+  addFrameReference(BuildMI(BB, X86::MOV8mi, 5),
+                    CWFrameIdx, 1).addImm(2);
+
+  // Reload the modified control word now.
+  addFrameReference(BuildMI(BB, X86::FLDCW16m, 4), CWFrameIdx);
+}
+
+void X86DAGToDAGISel::EmitFunctionEntryCode(Function &Fn, MachineFunction &MF) {
+  // If this is main, emit special code for main.
+  MachineBasicBlock *BB = MF.begin();
+  if (Fn.hasExternalLinkage() && Fn.getName() == "main")
+    EmitSpecialCodeForMain(BB, MF.getFrameInfo());
+}
+
 /// MatchAddress - Add the specified node to the specified addressing mode,
 /// returning true if it cannot be done.  This just pattern matches for the
 /// addressing mode
@@ -338,22 +363,25 @@ bool X86DAGToDAGISel::MatchAddress(SDOperand N, X86ISelAddressMode &AM) {
 bool X86DAGToDAGISel::SelectAddr(SDOperand N, SDOperand &Base, SDOperand &Scale,
                                  SDOperand &Index, SDOperand &Disp) {
   X86ISelAddressMode AM;
-  if (!MatchAddress(N, AM)) {
-    if (AM.BaseType == X86ISelAddressMode::RegBase) {
-      if (AM.Base.Reg.Val)
-        AM.Base.Reg = Select(AM.Base.Reg);
-      else
-        AM.Base.Reg = CurDAG->getRegister(0, MVT::i32);
-    }
-    if (AM.IndexReg.Val)
-      AM.IndexReg = Select(AM.IndexReg);
-    else
-      AM.IndexReg = CurDAG->getRegister(0, MVT::i32);
+  if (MatchAddress(N, AM))
+    return false;
 
-    getAddressOperands(AM, Base, Scale, Index, Disp);
-    return true;
+  if (AM.BaseType == X86ISelAddressMode::RegBase) {
+    if (AM.Base.Reg.Val) {
+      if (AM.Base.Reg.getOpcode() != ISD::Register)
+        AM.Base.Reg = Select(AM.Base.Reg);
+    } else {
+      AM.Base.Reg = CurDAG->getRegister(0, MVT::i32);
+    }
   }
-  return false;
+
+  if (AM.IndexReg.Val)
+    AM.IndexReg = Select(AM.IndexReg);
+  else
+    AM.IndexReg = CurDAG->getRegister(0, MVT::i32);
+
+  getAddressOperands(AM, Base, Scale, Index, Disp);
+  return true;
 }
 
 bool X86DAGToDAGISel::TryFoldLoad(SDOperand N, SDOperand &Base,

lib/Target/X86/X86ISelLowering.cpp

@@ -220,6 +220,8 @@ X86TargetLowering::LowerCallTo(SDOperand Chain, const Type *RetTy,
   // turn it into a TargetGlobalAddress node so that legalize doesn't hack it.
   if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
     Callee = DAG.getTargetGlobalAddress(G->getGlobal(), getPointerTy());
+  else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee))
+    Callee = DAG.getTargetExternalSymbol(S->getSymbol(), getPointerTy());
 
   if (CallingConv == CallingConv::Fast && EnableFastCC)
     return LowerFastCCCallTo(Chain, RetTy, isTailCall, Callee, Args, DAG);
@@ -412,8 +414,7 @@ X86TargetLowering::LowerCCCCallTo(SDOperand Chain, const Type *RetTy,
 
     // Arguments go on the stack in reverse order, as specified by the ABI.
     unsigned ArgOffset = 0;
-    SDOperand StackPtr = DAG.getCopyFromReg(DAG.getEntryNode(),
-                                            X86::ESP, MVT::i32);
+    SDOperand StackPtr = DAG.getRegister(X86::ESP, MVT::i32);
     std::vector<SDOperand> Stores;
 
     for (unsigned i = 0, e = Args.size(); i != e; ++i) {

lib/Target/X86/X86ISelPattern.cpp

@@ -1223,12 +1223,15 @@ unsigned ISel::SelectExpr(SDOperand N) {
   SDNode *Node = N.Val;
   SDOperand Op0, Op1;
 
-  if (Node->getOpcode() == ISD::CopyFromReg) {
-    unsigned Reg = cast<RegisterSDNode>(Node->getOperand(1))->getReg();
+  if (Node->getOpcode() == ISD::CopyFromReg ||
+      Node->getOpcode() == ISD::Register) {
+    unsigned Reg = (Node->getOpcode() == ISD::CopyFromReg) ?
+      cast<RegisterSDNode>(Node->getOperand(1))->getReg() :
+      cast<RegisterSDNode>(Node)->getReg();
     // Just use the specified register as our input if we can.
     if (MRegisterInfo::isVirtualRegister(Reg) || Reg == X86::ESP)
       return Reg;
-  }
+  } 
 
   unsigned &Reg = ExprMap[N];
   if (Reg) return Reg;

lib/Target/X86/X86InstrInfo.td

@@ -2916,8 +2916,8 @@ def RDTSC : I<0x31, RawFrm, (ops), "rdtsc", [(X86rdtsc)]>,
 // Calls
 def : Pat<(X86call tglobaladdr:$dst),
           (CALLpcrel32 tglobaladdr:$dst)>;
-def : Pat<(X86call externalsym:$dst),
-          (CALLpcrel32 externalsym:$dst)>;
+def : Pat<(X86call texternalsym:$dst),
+          (CALLpcrel32 texternalsym:$dst)>;
 
 // X86 specific add which produces a flag.
 def : Pat<(X86addflag R32:$src1, R32:$src2),