[mips] Reordering callseq* nodes to be linear

Fix nested callseq* nodes by moving callseq_start after the
arguments calculation to temporary registers, so that callseq* nodes
in resulting DAG are linear.

Differential Revision: https://reviews.llvm.org/D37328

llvm-svn: 314497

2 files changed, 27 insertions, 26 deletions

diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index 06874eb9796..5396de96ca5 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -2992,16 +2992,6 @@ MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   if (IsTailCall)
     ++NumTailCalls;
 
-  // Chain is the output chain of the last Load/Store or CopyToReg node.
-  // ByValChain is the output chain of the last Memcpy node created for copying
-  // byval arguments to the stack.
-  unsigned StackAlignment = TFL->getStackAlignment();
-  NextStackOffset = alignTo(NextStackOffset, StackAlignment);
-  SDValue NextStackOffsetVal = DAG.getIntPtrConstant(NextStackOffset, DL, true);
-
-  if (!IsTailCall)
-    Chain = DAG.getCALLSEQ_START(Chain, NextStackOffset, 0, DL);
-
   SDValue StackPtr =
       DAG.getCopyFromReg(Chain, DL, ABI.IsN64() ? Mips::SP_64 : Mips::SP,
                          getPointerTy(DAG.getDataLayout()));
@@ -3030,7 +3020,7 @@ MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
       assert(ByValIdx < CCInfo.getInRegsParamsCount());
       assert(!IsTailCall &&
              "Do not tail-call optimize if there is a byval argument.");
-      passByValArg(Chain, DL, RegsToPass, MemOpChains, StackPtr, MFI, DAG, Arg,
+      Chain = passByValArg(Chain, DL, RegsToPass, MemOpChains, StackPtr, MFI, DAG, Arg,
                    FirstByValReg, LastByValReg, Flags, Subtarget.isLittle(),
                    VA);
       CCInfo.nextInRegsParam();
@@ -3122,6 +3112,16 @@ MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   EVT Ty = Callee.getValueType();
   bool GlobalOrExternal = false, IsCallReloc = false;
 
+  // Chain is the output chain of the last Load/Store or CopyToReg node.
+  // ByValChain is the output chain of the last Memcpy node created for copying
+  // byval arguments to the stack.
+  unsigned StackAlignment = TFL->getStackAlignment();
+  NextStackOffset = alignTo(NextStackOffset, StackAlignment);
+  SDValue NextStackOffsetVal = DAG.getIntPtrConstant(NextStackOffset, DL, true);
+
+  if (!IsTailCall)
+    Chain = DAG.getCALLSEQ_START(Chain, NextStackOffset, 0, DL);
+
   // The long-calls feature is ignored in case of PIC.
   // While we do not support -mshared / -mno-shared properly,
   // ignore long-calls in case of -mabicalls too.
@@ -4095,7 +4095,7 @@ void MipsTargetLowering::copyByValRegs(
 }
 
 // Copy byVal arg to registers and stack.
-void MipsTargetLowering::passByValArg(
+SDValue MipsTargetLowering::passByValArg(
     SDValue Chain, const SDLoc &DL,
     std::deque<std::pair<unsigned, SDValue>> &RegsToPass,
     SmallVectorImpl<SDValue> &MemOpChains, SDValue StackPtr,
@@ -4128,7 +4128,7 @@ void MipsTargetLowering::passByValArg(
 
     // Return if the struct has been fully copied.
     if (ByValSizeInBytes == OffsetInBytes)
-      return;
+      return Chain;
 
     // Copy the remainder of the byval argument with sub-word loads and shifts.
     if (LeftoverBytes) {
@@ -4173,7 +4173,7 @@ void MipsTargetLowering::passByValArg(
 
       unsigned ArgReg = ArgRegs[FirstReg + I];
       RegsToPass.push_back(std::make_pair(ArgReg, Val));
-      return;
+      return Chain;
     }
   }
 
@@ -4183,12 +4183,13 @@ void MipsTargetLowering::passByValArg(
                             DAG.getConstant(OffsetInBytes, DL, PtrTy));
   SDValue Dst = DAG.getNode(ISD::ADD, DL, PtrTy, StackPtr,
                             DAG.getIntPtrConstant(VA.getLocMemOffset(), DL));
-  Chain = DAG.getMemcpy(Chain, DL, Dst, Src,
-                        DAG.getConstant(MemCpySize, DL, PtrTy),
-                        Alignment, /*isVolatile=*/false, /*AlwaysInline=*/false,
-                        /*isTailCall=*/false,
-                        MachinePointerInfo(), MachinePointerInfo());
+  Chain = DAG.getMemcpy(
+      Chain, DL, Dst, Src, DAG.getConstant(MemCpySize, DL, PtrTy), Alignment,
+      /*isVolatile=*/false, /*AlwaysInline=*/false,
+      /*isTailCall=*/false, MachinePointerInfo(), MachinePointerInfo());
   MemOpChains.push_back(Chain);
+
+  return Chain;
 }
 
 void MipsTargetLowering::writeVarArgRegs(std::vector<SDValue> &OutChains,
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.h b/llvm/lib/Target/Mips/MipsISelLowering.h
index 4933cc1eb21..b155332f786 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.h
+++ b/llvm/lib/Target/Mips/MipsISelLowering.h
@@ -573,13 +573,13 @@ class TargetRegisterClass;
                        MipsCCState &State) const;
 
     /// passByValArg - Pass a byval argument in registers or on stack.
-    void passByValArg(SDValue Chain, const SDLoc &DL,
-                      std::deque<std::pair<unsigned, SDValue>> &RegsToPass,
-                      SmallVectorImpl<SDValue> &MemOpChains, SDValue StackPtr,
-                      MachineFrameInfo &MFI, SelectionDAG &DAG, SDValue Arg,
-                      unsigned FirstReg, unsigned LastReg,
-                      const ISD::ArgFlagsTy &Flags, bool isLittle,
-                      const CCValAssign &VA) const;
+    SDValue passByValArg(SDValue Chain, const SDLoc &DL,
+                         std::deque<std::pair<unsigned, SDValue>> &RegsToPass,
+                         SmallVectorImpl<SDValue> &MemOpChains,
+                         SDValue StackPtr, MachineFrameInfo &MFI,
+                         SelectionDAG &DAG, SDValue Arg, unsigned FirstReg,
+                         unsigned LastReg, const ISD::ArgFlagsTy &Flags,
+                         bool isLittle, const CCValAssign &VA) const;
 
     /// writeVarArgRegs - Write variable function arguments passed in registers
     /// to the stack. Also create a stack frame object for the first variable