Fix an obscure issue in X86_64 parameter passing: if a tiny byval is

passed as the fifth parameter, insure it's passed correctly (in R9).
rdar://problem/6920088


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131467 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CallingConvLower.cpp

@@ -48,8 +48,12 @@ void CCState::HandleByVal(unsigned ValNo, MVT ValVT,
   if (MinAlign > (int)Align)
     Align = MinAlign;
   TM.getTargetLowering()->HandleByVal(const_cast<CCState*>(this), Size);
+  if (Size != 0) {
     unsigned Offset = AllocateStack(Size, Align);
     addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
+  } else {
+    addLoc(CCValAssign::getReg(ValNo, ValVT, getFirstByValReg(), LocVT, LocInfo));
+  }
 }
 
 /// MarkAllocated - Mark a register and all of its aliases as allocated.

lib/Target/X86/X86ISelLowering.cpp

@@ -2091,6 +2091,22 @@ X86TargetLowering::LowerCall(SDValue Chain, SDValue Callee,
     }
 
     if (VA.isRegLoc()) {
+      if (isByVal && (!IsSibcall && !isTailCall)) {
+        // 64-bit only.  x86_32 passes everything on the stack.
+        assert(CCInfo.isFirstByValRegValid() && "isByVal, but no valid register assigned!");
+        EVT PtrVT = DAG.getTargetLoweringInfo().getPointerTy();
+        unsigned int i, j;
+        for (i = 0, j = CCInfo.getFirstByValReg(); j <= X86::R9; i++, j++) {
+          SDValue Const = DAG.getConstant(8*i, MVT::i64);
+          SDValue AddArg = DAG.getNode(ISD::ADD, dl, PtrVT, Arg, Const);
+          SDValue Load = DAG.getLoad(PtrVT, dl, Chain, AddArg,
+                                     MachinePointerInfo(),
+                                     false, false, 0);
+          MemOpChains.push_back(Load.getValue(1));
+          RegsToPass.push_back(std::make_pair(j, Load));
+        }
+        CCInfo.clearFirstByValReg();
+      } else {
         RegsToPass.push_back(std::make_pair(VA.getLocReg(), Arg));
         if (isVarArg && IsWin64) {
           // Win64 ABI requires argument XMM reg to be copied to the corresponding
@@ -2105,6 +2121,7 @@ X86TargetLowering::LowerCall(SDValue Chain, SDValue Callee,
           if (ShadowReg)
             RegsToPass.push_back(std::make_pair(ShadowReg, Arg));
         }
+      }
     } else if (!IsSibcall && (!isTailCall || isByVal)) {
       assert(VA.isMemLoc());
       if (StackPtr.getNode() == 0)
@@ -2438,6 +2455,47 @@ X86TargetLowering::GetAlignedArgumentStackSize(unsigned StackSize,
   return Offset;
 }
 
+/// HandleByVal - Every parameter *after* a byval parameter is passed
+/// on the stack.  Remember the next parameter register to allocate,
+/// and then confiscate the rest of the parameter registers to insure
+/// this.
+void
+X86TargetLowering::HandleByVal(CCState *State, unsigned &size) const {
+  // X86_32 passes all parameters on the stack, byval or whatever.
+  // X86_64 does not split parameters between registers and memory; if
+  // the parameter does not fit entirely inside the remaining
+  // parameter registers, it goes on the stack.
+  static const unsigned RegList2[] = {
+    X86::RDI, X86::RSI, X86::RDX, X86::RCX, X86::R8, X86::R9
+  };
+
+  if (!Subtarget->is64Bit())
+    return;
+
+  if (size > 16) // X86_64 aggregates > 16 bytes are passed in memory.
+    return;
+
+  unsigned reg = State->getFirstUnallocated(RegList2, 6);
+
+  if (reg == 6) // Out of regs to allocate.
+    return;
+
+  // We expect the size to be 32 bits, or some non-zero multiple of 64 bits.
+  unsigned nregs = size / 8;
+  if (nregs == 0) nregs=1;      // 32-bit case.
+
+  unsigned regs_available = 6 - reg;
+
+  if (nregs <= regs_available) {
+    size = 0;
+    State->setFirstByValReg(RegList2[reg]);
+    while (nregs--) {
+      State->AllocateReg(RegList2[reg]);
+      reg++;
+    }
+  }
+}
+
 /// MatchingStackOffset - Return true if the given stack call argument is
 /// already available in the same position (relatively) of the caller's
 /// incoming argument stack.
@@ -2602,7 +2660,7 @@ X86TargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
     }
 
     CCInfo.AnalyzeCallOperands(Outs, CC_X86);
-    if (CCInfo.getNextStackOffset()) {
+    if (ArgLocs.size()) {
       MachineFunction &MF = DAG.getMachineFunction();
       if (MF.getInfo<X86MachineFunctionInfo>()->getBytesToPopOnReturn())
         return false;
@@ -2619,6 +2677,8 @@ X86TargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
         ISD::ArgFlagsTy Flags = Outs[i].Flags;
         if (VA.getLocInfo() == CCValAssign::Indirect)
           return false;
+        if (Flags.isByVal())
+          return false;
         if (!VA.isRegLoc()) {
           if (!MatchingStackOffset(Arg, VA.getLocMemOffset(), Flags,
                                    MFI, MRI, TII))

lib/Target/X86/X86ISelLowering.h

@@ -728,6 +728,8 @@ namespace llvm {
 
     // Call lowering helpers.
 
+    void HandleByVal(CCState *, unsigned &) const;
+
     /// IsEligibleForTailCallOptimization - Check whether the call is eligible
     /// for tail call optimization. Targets which want to do tail call
     /// optimization should implement this function.