[tablegen] Add CustomCallingConv and use it to tablegen-erate the outermost parts of the Mips O32 implementation

Summary:
CustomCallingConv is simply a CallingConv that tablegen should not generate the
implementation for. It allows regular CallingConv's to delegate to these custom
functions. This is (currently) necessary for Mips and we cannot use CCCustom
without having to adapt to the different API that CCCustom uses.

This brings us a bit closer to being able to remove
MipsCC::analyzeCallOperands and MipsCC::analyzeFormalArguments in favour of
the common implementation.

No functional change to the targets.

Depends on D3341

Reviewers: vmedic

Reviewed By: vmedic

Subscribers: vmedic, llvm-commits

Differential Revision: http://reviews.llvm.org/D5965

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221052 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetCallingConv.td

@@ -147,6 +147,13 @@ class CCDelegateTo<CallingConv cc> : CCAction {
 /// that the target supports.
 class CallingConv<list<CCAction> actions> {
   list<CCAction> Actions = actions;
+  bit Custom = 0;
+}
+
+/// CustomCallingConv - An instance of this is used to declare calling
+/// conventions that are implemented using a custom function of the same name.
+class CustomCallingConv : CallingConv<[]> {
+  let Custom = 1;
 }
 
 /// CalleeSavedRegs - A list of callee saved registers for a given calling

lib/Target/Mips/MipsCallingConv.td

@@ -66,6 +66,14 @@ def RetCC_MipsO32 : CallingConv<[
   CCIfType<[f64], CCIfSubtargetNot<"isFP64bit()", CCAssignToReg<[D0, D1]>>>
 ]>;
 
+def CC_MipsO32_FP32 : CustomCallingConv;
+def CC_MipsO32_FP64 : CustomCallingConv;
+
+def CC_MipsO32_FP : CallingConv<[
+  CCIfSubtargetNot<"isFP64bit()", CCDelegateTo<CC_MipsO32_FP32>>,
+  CCIfSubtarget<"isFP64bit()", CCDelegateTo<CC_MipsO32_FP64>>
+]>;
+
 //===----------------------------------------------------------------------===//
 // Mips N32/64 Calling Convention
 //===----------------------------------------------------------------------===//
@@ -289,6 +297,22 @@ def RetCC_Mips : CallingConv<[
   CCDelegateTo<RetCC_MipsO32>
 ]>;
 
+def CC_Mips_FixedArg : CallingConv<[
+  CCIfCC<"CallingConv::Fast", CCDelegateTo<CC_Mips_FastCC>>,
+
+  // FIXME: There wasn't an EABI case in the original code and it seems unlikely
+  //        that it's the same as CC_MipsN
+  CCIfSubtarget<"isABI_O32()", CCDelegateTo<CC_MipsO32_FP>>,
+  CCDelegateTo<CC_MipsN>
+]>;
+
+def CC_Mips_VarArg : CallingConv<[
+  // FIXME: There wasn't an EABI case in the original code and it seems unlikely
+  //        that it's the same as CC_MipsN_VarArg
+  CCIfSubtarget<"isABI_O32()", CCDelegateTo<CC_MipsO32_FP>>,
+  CCDelegateTo<CC_MipsN_VarArg>
+]>;
+
 //===----------------------------------------------------------------------===//
 // Callee-saved register lists.
 //===----------------------------------------------------------------------===//

lib/Target/Mips/MipsISelLowering.cpp

@@ -3548,7 +3548,7 @@ analyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Args,
          "CallingConv::Fast shouldn't be used for vararg functions.");
 
   unsigned NumOpnds = Args.size();
-  llvm::CCAssignFn *FixedFn = fixedArgFn(), *VarFn = varArgFn();
+  llvm::CCAssignFn *FixedFn = fixedArgFn();
 
   for (unsigned I = 0; I != NumOpnds; ++I) {
     MVT ArgVT = Args[I].VT;
@@ -3561,7 +3561,7 @@ analyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Args,
     }
 
     if (IsVarArg && !Args[I].IsFixed)
-      R = VarFn(I, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, CCInfo);
+      R = CC_Mips_VarArg(I, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, CCInfo);
     else {
       MVT RegVT = getRegVT(ArgVT, FuncArgs[Args[I].OrigArgIndex].Ty, CallNode,
                            IsSoftFloat);
@@ -3644,20 +3644,11 @@ const ArrayRef<MCPhysReg> MipsTargetLowering::MipsCC::intArgRegs() const {
 }
 
 llvm::CCAssignFn *MipsTargetLowering::MipsCC::fixedArgFn() const {
-  if (CallConv == CallingConv::Fast)
-    return CC_Mips_FastCC;
-
-  if (SpecialCallingConv == Mips16RetHelperConv)
+  if (CallConv != CallingConv::Fast &&
+      SpecialCallingConv == Mips16RetHelperConv)
     return CC_Mips16RetHelper;
-  return Subtarget.isABI_O32()
-             ? (Subtarget.isFP64bit() ? CC_MipsO32_FP64 : CC_MipsO32_FP32)
-             : CC_MipsN;
-}
 
-llvm::CCAssignFn *MipsTargetLowering::MipsCC::varArgFn() const {
-  return Subtarget.isABI_O32()
-             ? (Subtarget.isFP64bit() ? CC_MipsO32_FP64 : CC_MipsO32_FP32)
-             : CC_MipsN_VarArg;
+  return CC_Mips_FixedArg;
 }
 
 const MCPhysReg *MipsTargetLowering::MipsCC::shadowRegs() const {

lib/Target/Mips/MipsISelLowering.h

@@ -396,9 +396,6 @@ namespace llvm {
       /// Return the function that analyzes fixed argument list functions.
       llvm::CCAssignFn *fixedArgFn() const;
 
-      /// Return the function that analyzes variable argument list functions.
-      llvm::CCAssignFn *varArgFn() const;
-
       const MCPhysReg *shadowRegs() const;
 
       void allocateRegs(ByValArgInfo &ByVal, unsigned ByValSize,

utils/TableGen/CallingConvEmitter.cpp

@@ -35,23 +35,26 @@ private:
 } // End anonymous namespace
 
 void CallingConvEmitter::run(raw_ostream &O) {
-
   std::vector<Record*> CCs = Records.getAllDerivedDefinitions("CallingConv");
-  
-  // Emit prototypes for all of the CC's so that they can forward ref each
-  // other.
+
+  // Emit prototypes for all of the non-custom CC's so that they can forward ref
+  // each other.
   for (unsigned i = 0, e = CCs.size(); i != e; ++i) {
-    O << "static bool " << CCs[i]->getName()
-      << "(unsigned ValNo, MVT ValVT,\n"
-      << std::string(CCs[i]->getName().size()+13, ' ')
-      << "MVT LocVT, CCValAssign::LocInfo LocInfo,\n"
-      << std::string(CCs[i]->getName().size()+13, ' ')
-      << "ISD::ArgFlagsTy ArgFlags, CCState &State);\n";
+    if (!CCs[i]->getValueAsBit("Custom")) {
+      O << "static bool " << CCs[i]->getName()
+        << "(unsigned ValNo, MVT ValVT,\n"
+        << std::string(CCs[i]->getName().size() + 13, ' ')
+        << "MVT LocVT, CCValAssign::LocInfo LocInfo,\n"
+        << std::string(CCs[i]->getName().size() + 13, ' ')
+        << "ISD::ArgFlagsTy ArgFlags, CCState &State);\n";
+    }
+  }
+
+  // Emit each non-custom calling convention description in full.
+  for (unsigned i = 0, e = CCs.size(); i != e; ++i) {
+    if (!CCs[i]->getValueAsBit("Custom"))
+      EmitCallingConv(CCs[i], O);
   }
-  
-  // Emit each calling convention description in full.
-  for (unsigned i = 0, e = CCs.size(); i != e; ++i)
-    EmitCallingConv(CCs[i], O);
 }