Checkin in of first of several patches to finish implementation of

mips16/mips32 floating point interoperability. 

This patch fixes returns from mips16 functions so that if the function
was in fact called by a mips32 hard float routine, then values
that would have been returned in floating point registers are so returned.

Mips16 mode has no floating point instructions so there is no way to
load values into floating point registers.

This is needed when returning float, double, single complex, double complex
in the Mips ABI.

Helper functions in libc for mips16 are available to do this.

For efficiency purposes, these helper functions have a different calling
convention from normal Mips calls.

Registers v0,v1,a0,a1 are used to pass parameters instead of
a0,a1,a2,a3.

This is because v0,v1,a0,a1 are the natural registers used to return
floating point values in soft float. These values can then be moved
to the appropriate floating point registers with no extra cost.

The only register that is modified is ra in this call.

The helper functions make sure that the return values are in the floating
point registers that they would be in if soft float was not in effect
(which it is for mips16, though the soft float is implemented using a mips32
library that uses hard float).
 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181641 91177308-0d34-0410-b5e6-96231b3b80d8

12 files changed, 282 insertions, 16 deletions

diff --git a/lib/Target/Mips/CMakeLists.txt b/lib/Target/Mips/CMakeLists.txt
index 78a9f70c66..8be68c5b4f 100644
--- a/lib/Target/Mips/CMakeLists.txt
+++ b/lib/Target/Mips/CMakeLists.txt
@@ -15,6 +15,7 @@ add_public_tablegen_target(MipsCommonTableGen)
 
 add_llvm_target(MipsCodeGen
   Mips16FrameLowering.cpp
+  Mips16HardFloat.cpp
   Mips16InstrInfo.cpp
   Mips16ISelDAGToDAG.cpp
   Mips16ISelLowering.cpp
diff --git a/lib/Target/Mips/Mips16HardFloat.cpp b/lib/Target/Mips/Mips16HardFloat.cpp
new file mode 100644
index 0000000000..4d1e61bb99
--- /dev/null
+++ b/lib/Target/Mips/Mips16HardFloat.cpp
@@ -0,0 +1,141 @@
+//===---- Mips16HardFloat.cpp for Mips16 Hard Float               --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a pass needed for Mips16 Hard Float
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "mips16-hard-float"
+#include "Mips16HardFloat.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include <string>
+
+//
+// Return types that matter for hard float are:
+// float, double, complex float, and complex double
+//
+enum FPReturnVariant {
+  FRet, DRet, CFRet, CDRet, NoFPRet
+};
+
+//
+// Determine which FP return type this function has
+//
+static FPReturnVariant whichFPReturnVariant(Type *T) {
+  switch (T->getTypeID()) {
+  case Type::FloatTyID:
+    return FRet;
+  case Type::DoubleTyID:
+    return DRet;
+  case Type::StructTyID:
+    if (T->getStructNumElements() != 2)
+      break;
+    if ((T->getContainedType(0)->isFloatTy()) &&
+        (T->getContainedType(1)->isFloatTy()))
+      return CFRet;
+    if ((T->getContainedType(0)->isDoubleTy()) &&
+        (T->getContainedType(1)->isDoubleTy()))
+      return CDRet;
+    break;
+  default:
+    break;
+  }
+  return NoFPRet;
+}
+
+//
+// Returns of float, double and complex need to be handled with a helper
+// function. The "AndCal" part is coming in a later patch.
+//
+static bool fixupFPReturnAndCall
+  (Function &F, Module *M,  const MipsSubtarget &Subtarget) {
+  bool Modified = false;
+  LLVMContext &C = M->getContext();
+  Type *MyVoid = Type::getVoidTy(C);
+  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+    for (BasicBlock::iterator I = BB->begin(), E = BB->end();
+         I != E; ++I) {
+      Instruction &Inst = *I;
+      if (const ReturnInst *RI = dyn_cast<ReturnInst>(I)) {
+        Value *RVal = RI->getReturnValue();
+        if (!RVal) continue;
+        //
+        // If there is a return value and it needs a helper function,
+        // figure out which one and add a call before the actual
+        // return to this helper. The purpose of the helper is to move
+        // floating point values from their soft float return mapping to
+        // where they would have been mapped to in floating point registers.
+        //
+        Type *T = RVal->getType();
+        FPReturnVariant RV = whichFPReturnVariant(T);
+        if (RV == NoFPRet) continue;
+        static const char* Helper[NoFPRet] =
+          {"__mips16_ret_sf", "__mips16_ret_df", "__mips16_ret_sc",
+           "__mips16_ret_dc"};
+        const char *Name = Helper[RV];
+        AttributeSet A;
+        Value *Params[] = {RVal};
+        Modified = true;
+        //
+        // These helper functions have a different calling ABI so
+        // this __Mips16RetHelper indicates that so that later
+        // during call setup, the proper call lowering to the helper
+        // functions will take place.
+        //
+        A = A.addAttribute(C, AttributeSet::FunctionIndex,
+                           "__Mips16RetHelper");
+        A = A.addAttribute(C, AttributeSet::FunctionIndex,
+                           Attribute::ReadNone);
+        Value *F = (M->getOrInsertFunction(Name, A, MyVoid, T, NULL));
+        CallInst::Create(F, Params, "", &Inst );
+      }
+    }
+  return Modified;
+}
+
+namespace llvm {
+
+//
+// This pass only makes sense when the underlying chip has floating point but
+// we are compiling as mips16.
+// For all mips16 functions (that are not stubs we have already generated), or
+// declared via attributes as nomips16, we must:
+//    1) fixup all returns of float, double, single and double complex
+//       by calling a helper function before the actual return.
+//    2) generate helper functions (stubs) that can be called by mips32 functions
+//       that will move parameters passed normally passed in floating point
+//       registers the soft float equivalents. (Coming in a later patch).
+//    3) in the case of static relocation, generate helper functions so that
+//       mips16 functions can call extern functions of unknown type (mips16 or
+//       mips32). (Coming in a later patch).
+//    4) TBD. For pic, calls to extern functions of unknown type are handled by
+//       predefined helper functions in libc but this work is currently done
+//       during call lowering but it should be moved here in the future.
+//
+bool Mips16HardFloat::runOnModule(Module &M) {
+  DEBUG(errs() << "Run on Module Mips16HardFloat\n");
+  bool Modified = false;
+  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+    if (F->isDeclaration() || F->hasFnAttribute("mips16_fp_stub") ||
+        F->hasFnAttribute("nomips16")) continue;
+    Modified |= fixupFPReturnAndCall(*F, &M, Subtarget);
+  }
+  return Modified;
+}
+
+char Mips16HardFloat::ID = 0;
+
+}
+
+ModulePass *llvm::createMips16HardFloat(MipsTargetMachine &TM) {
+  return new Mips16HardFloat(TM);
+}
+
diff --git a/lib/Target/Mips/Mips16HardFloat.h b/lib/Target/Mips/Mips16HardFloat.h
new file mode 100644
index 0000000000..b7f712af5b
--- /dev/null
+++ b/lib/Target/Mips/Mips16HardFloat.h
@@ -0,0 +1,54 @@
+//===---- Mips16HardFloat.h for Mips16 Hard Float                  --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a phase which implements part of the floating point
+// interoperability between Mips16 and Mips32 code.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/MipsMCTargetDesc.h"
+#include "MipsTargetMachine.h"
+#include "llvm/Pass.h"
+#include "llvm/Target/TargetMachine.h"
+
+
+#ifndef MIPS16HARDFLOAT_H
+#define MIPS16HARDFLOAT_H
+
+using namespace llvm;
+
+namespace llvm {
+
+class Mips16HardFloat : public ModulePass {
+
+public:
+  static char ID;
+
+  Mips16HardFloat(MipsTargetMachine &TM_) : ModulePass(ID),
+    TM(TM_), Subtarget(TM.getSubtarget<MipsSubtarget>()) {
+  }
+
+  virtual const char *getPassName() const {
+    return "MIPS16 Hard Float Pass";
+  }
+
+  virtual bool runOnModule(Module &M);
+
+protected:
+  /// Keep a pointer to the MipsSubtarget around so that we can make the right
+  /// decision when generating code for different targets.
+  const TargetMachine &TM;
+  const MipsSubtarget &Subtarget;
+
+};
+
+ModulePass *createMips16HardFloat(MipsTargetMachine &TM);
+
+}
+#endif
diff --git a/lib/Target/Mips/Mips16ISelLowering.cpp b/lib/Target/Mips/Mips16ISelLowering.cpp
index f63318f1e6..c633d312bb 100644
--- a/lib/Target/Mips/Mips16ISelLowering.cpp
+++ b/lib/Target/Mips/Mips16ISelLowering.cpp
@@ -13,6 +13,7 @@
 #define DEBUG_TYPE "mips-lower"
 #include "Mips16ISelLowering.h"
 #include "MipsRegisterInfo.h"
+#include "MipsTargetMachine.h"
 #include "MCTargetDesc/MipsBaseInfo.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/Support/CommandLine.h"
@@ -21,11 +22,6 @@
 
 using namespace llvm;
 
-static cl::opt<bool>
-Mips16HardFloat("mips16-hard-float", cl::NotHidden,
-                cl::desc("MIPS: mips16 hard float enable."),
-                cl::init(false));
-
 static cl::opt<bool> DontExpandCondPseudos16(
   "mips16-dont-expand-cond-pseudo",
   cl::init(false),
@@ -50,7 +46,7 @@ Mips16TargetLowering::Mips16TargetLowering(MipsTargetMachine &TM)
   // Set up the register classes
   addRegisterClass(MVT::i32, &Mips::CPU16RegsRegClass);
 
-  if (Mips16HardFloat)
+  if (Subtarget->inMips16HardFloat())
     setMips16HardFloatLibCalls();
 
   setOperationAction(ISD::ATOMIC_FENCE,       MVT::Other, Expand);
@@ -374,7 +370,8 @@ getOpndList(SmallVectorImpl<SDValue> &Ops,
   const char* Mips16HelperFunction = 0;
   bool NeedMips16Helper = false;
 
-  if (getTargetMachine().Options.UseSoftFloat && Mips16HardFloat) {
+  if (getTargetMachine().Options.UseSoftFloat &&
+      Subtarget->inMips16HardFloat()) {
     //
     // currently we don't have symbols tagged with the mips16 or mips32
     // qualifier so we will assume that we don't know what kind it is.
diff --git a/lib/Target/Mips/MipsCallingConv.td b/lib/Target/Mips/MipsCallingConv.td
index 462def76cc..6e8c5d24a8 100644
--- a/lib/Target/Mips/MipsCallingConv.td
+++ b/lib/Target/Mips/MipsCallingConv.td
@@ -196,6 +196,13 @@ def CC_Mips_FastCC : CallingConv<[
   CCDelegateTo<CC_MipsN_FastCC>
 ]>;
 
+//==
+
+def CC_Mips16RetHelper : CallingConv<[
+  // Integer arguments are passed in integer registers.
+  CCIfType<[i32], CCAssignToReg<[V0, V1, A0, A1]>>
+]>;
+
 //===----------------------------------------------------------------------===//
 // Mips Calling Convention Dispatch
 //===----------------------------------------------------------------------===//
@@ -223,3 +230,6 @@ def CSR_N32 : CalleeSavedRegs<(add D31_64, D29_64, D27_64, D25_64, D24_64,
 
 def CSR_N64 : CalleeSavedRegs<(add (sequence "D%u_64", 31, 24), RA_64, FP_64,
                                    GP_64, (sequence "S%u_64", 7, 0))>;
+
+def CSR_Mips16RetHelper : 
+  CalleeSavedRegs<(add V0, V1, (sequence "A%u", 3, 0), S0, S1)>;
diff --git a/lib/Target/Mips/MipsISelLowering.cpp b/lib/Target/Mips/MipsISelLowering.cpp
index 4d76181f92..ab105b3655 100644
--- a/lib/Target/Mips/MipsISelLowering.cpp
+++ b/lib/Target/Mips/MipsISelLowering.cpp
@@ -2229,6 +2229,15 @@ getOpndList(SmallVectorImpl<SDValue> &Ops,
   const TargetRegisterInfo *TRI = getTargetMachine().getRegisterInfo();
   const uint32_t *Mask = TRI->getCallPreservedMask(CLI.CallConv);
   assert(Mask && "Missing call preserved mask for calling convention");
+  if (Subtarget->inMips16HardFloat()) {
+    if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(CLI.Callee)) {
+      llvm::StringRef Sym = G->getGlobal()->getName();
+      Function *F = G->getGlobal()->getParent()->getFunction(Sym);
+      if (F->hasFnAttribute("__Mips16RetHelper")) {
+        Mask = MipsRegisterInfo::getMips16RetHelperMask();
+      }
+    }
+  }
   Ops.push_back(CLI.DAG.getRegisterMask(Mask));
 
   if (InFlag.getNode())
@@ -2260,7 +2269,9 @@ MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   SmallVector<CCValAssign, 16> ArgLocs;
   CCState CCInfo(CallConv, IsVarArg, DAG.getMachineFunction(),
                  getTargetMachine(), ArgLocs, *DAG.getContext());
-  MipsCC MipsCCInfo(CallConv, IsO32, CCInfo);
+  MipsCC::SpecialCallingConvType SpecialCallingConv =
+    getSpecialCallingConv(Callee);
+  MipsCC MipsCCInfo(CallConv, IsO32, CCInfo, SpecialCallingConv);
 
   MipsCCInfo.analyzeCallOperands(Outs, IsVarArg,
                                  getTargetMachine().Options.UseSoftFloat,
@@ -3029,13 +3040,32 @@ static bool originalTypeIsF128(const Type *Ty, const SDNode *CallNode) {
   return (ES && Ty->isIntegerTy(128) && isF128SoftLibCall(ES->getSymbol()));
 }
 
-MipsTargetLowering::MipsCC::MipsCC(CallingConv::ID CC, bool IsO32_,
-                                   CCState &Info)
-  : CCInfo(Info), CallConv(CC), IsO32(IsO32_) {
+MipsTargetLowering::MipsCC::SpecialCallingConvType
+  MipsTargetLowering::getSpecialCallingConv(SDValue Callee) const {
+  MipsCC::SpecialCallingConvType SpecialCallingConv =
+    MipsCC::NoSpecialCallingConv;;
+  if (Subtarget->inMips16HardFloat()) {
+    if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
+      llvm::StringRef Sym = G->getGlobal()->getName();
+      Function *F = G->getGlobal()->getParent()->getFunction(Sym);
+      if (F->hasFnAttribute("__Mips16RetHelper")) {
+        SpecialCallingConv = MipsCC::Mips16RetHelperConv;
+      }
+    }
+  }
+  return SpecialCallingConv;
+}
+
+MipsTargetLowering::MipsCC::MipsCC(
+  CallingConv::ID CC, bool IsO32_, CCState &Info,
+    MipsCC::SpecialCallingConvType SpecialCallingConv_)
+  : CCInfo(Info), CallConv(CC), IsO32(IsO32_),
+    SpecialCallingConv(SpecialCallingConv_){
   // Pre-allocate reserved argument area.
   CCInfo.AllocateStack(reservedArgArea(), 1);
 }
 
+
 void MipsTargetLowering::MipsCC::
 analyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Args,
                     bool IsVarArg, bool IsSoftFloat, const SDNode *CallNode,
@@ -3183,6 +3213,8 @@ llvm::CCAssignFn *MipsTargetLowering::MipsCC::fixedArgFn() const {
   if (CallConv == CallingConv::Fast)
     return CC_Mips_FastCC;
 
+  if (SpecialCallingConv == Mips16RetHelperConv)
+    return CC_Mips16RetHelper;
   return IsO32 ? CC_MipsO32 : CC_MipsN;
 }
 
diff --git a/lib/Target/Mips/MipsISelLowering.h b/lib/Target/Mips/MipsISelLowering.h
index 5587e8f581..233c11f789 100644
--- a/lib/Target/Mips/MipsISelLowering.h
+++ b/lib/Target/Mips/MipsISelLowering.h
@@ -240,7 +240,14 @@ namespace llvm {
     /// arguments and inquire about calling convention information.
     class MipsCC {
     public:
-      MipsCC(CallingConv::ID CallConv, bool IsO32, CCState &Info);
+      enum SpecialCallingConvType {
+        Mips16RetHelperConv, NoSpecialCallingConv
+      };
+
+      MipsCC(
+        CallingConv::ID CallConv, bool IsO32, CCState &Info,
+        SpecialCallingConvType SpecialCallingConv = NoSpecialCallingConv);
+
 
       void analyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
                                bool IsVarArg, bool IsSoftFloat,
@@ -313,15 +320,18 @@ namespace llvm {
       CCState &CCInfo;
       CallingConv::ID CallConv;
       bool IsO32;
+      SpecialCallingConvType SpecialCallingConv;
       SmallVector<ByValArgInfo, 2> ByValArgs;
     };
-
+  protected:
     // Subtarget Info
     const MipsSubtarget *Subtarget;
 
     bool HasMips64, IsN64, IsO32;
 
   private:
+
+    MipsCC::SpecialCallingConvType getSpecialCallingConv(SDValue Callee) const;
     // Lower Operand helpers
     SDValue LowerCallResult(SDValue Chain, SDValue InFlag,
                             CallingConv::ID CallConv, bool isVarArg,
diff --git a/lib/Target/Mips/MipsRegisterInfo.cpp b/lib/Target/Mips/MipsRegisterInfo.cpp
index dead07bacd..ae25e456d5 100644
--- a/lib/Target/Mips/MipsRegisterInfo.cpp
+++ b/lib/Target/Mips/MipsRegisterInfo.cpp
@@ -100,6 +100,10 @@ MipsRegisterInfo::getCallPreservedMask(CallingConv::ID) const {
   return CSR_N64_RegMask;
 }
 
+const uint32_t *MipsRegisterInfo::getMips16RetHelperMask() {
+  return CSR_Mips16RetHelper_RegMask;
+}
+
 BitVector MipsRegisterInfo::
 getReservedRegs(const MachineFunction &MF) const {
   static const uint16_t ReservedCPURegs[] = {
diff --git a/lib/Target/Mips/MipsRegisterInfo.h b/lib/Target/Mips/MipsRegisterInfo.h
index 5ed5124139..20ba41d7fd 100644
--- a/lib/Target/Mips/MipsRegisterInfo.h
+++ b/lib/Target/Mips/MipsRegisterInfo.h
@@ -46,6 +46,7 @@ public:
                                MachineFunction &MF) const;
   const uint16_t *getCalleeSavedRegs(const MachineFunction *MF = 0) const;
   const uint32_t *getCallPreservedMask(CallingConv::ID) const;
+  static const uint32_t *getMips16RetHelperMask();
 
   BitVector getReservedRegs(const MachineFunction &MF) const;
 
diff --git a/lib/Target/Mips/MipsSubtarget.cpp b/lib/Target/Mips/MipsSubtarget.cpp
index 14a2b27795..259e68df32 100644
--- a/lib/Target/Mips/MipsSubtarget.cpp
+++ b/lib/Target/Mips/MipsSubtarget.cpp
@@ -48,6 +48,11 @@ static cl::opt<bool> Mips_Os16(
            "floating point as Mips 16"),
   cl::Hidden);
 
+static cl::opt<bool>
+Mips16HardFloat("mips16-hard-float", cl::NotHidden,
+                cl::desc("MIPS: mips16 hard float enable."),
+                cl::init(false));
+
 void MipsSubtarget::anchor() { }
 
 MipsSubtarget::MipsSubtarget(const std::string &TT, const std::string &CPU,
@@ -58,7 +63,8 @@ MipsSubtarget::MipsSubtarget(const std::string &TT, const std::string &CPU,
   IsSingleFloat(false), IsFP64bit(false), IsGP64bit(false), HasVFPU(false),
   IsLinux(true), HasSEInReg(false), HasCondMov(false), HasSwap(false),
   HasBitCount(false), HasFPIdx(false),
-  InMips16Mode(false), InMicroMipsMode(false), HasDSP(false), HasDSPR2(false),
+  InMips16Mode(false), InMips16HardFloat(Mips16HardFloat),
+  InMicroMipsMode(false), HasDSP(false), HasDSPR2(false),
   AllowMixed16_32(Mixed16_32 | Mips_Os16), Os16(Mips_Os16),
   RM(_RM), OverrideMode(NoOverride), TM(_TM)
 {
diff --git a/lib/Target/Mips/MipsSubtarget.h b/lib/Target/Mips/MipsSubtarget.h
index f2f0e15887..ef7568a813 100644
--- a/lib/Target/Mips/MipsSubtarget.h
+++ b/lib/Target/Mips/MipsSubtarget.h
@@ -93,6 +93,9 @@ protected:
   // InMips16 -- can process Mips16 instructions
   bool InMips16Mode;
 
+  // Mips16 hard float
+  bool InMips16HardFloat;
+
   // PreviousInMips16 -- the function we just processed was in Mips 16 Mode
   bool PreviousInMips16Mode;
 
@@ -170,9 +173,12 @@ public:
     }
     llvm_unreachable("Unexpected mode");
   }
-  bool inMips16ModeDefault() {
+  bool inMips16ModeDefault() const {
     return InMips16Mode;
   }
+  bool inMips16HardFloat() const {
+    return inMips16Mode() && InMips16HardFloat;
+  }
   bool inMicroMipsMode() const { return InMicroMipsMode; }
   bool hasDSP() const { return HasDSP; }
   bool hasDSPR2() const { return HasDSPR2; }
@@ -188,7 +194,8 @@ public:
   bool hasBitCount()  const { return HasBitCount; }
   bool hasFPIdx()     const { return HasFPIdx; }
 
-  bool allowMixed16_32() const { return AllowMixed16_32;};
+  bool allowMixed16_32() const { return inMips16ModeDefault() |
+                                        AllowMixed16_32;}
 
   bool os16() const { return Os16;};
 
diff --git a/lib/Target/Mips/MipsTargetMachine.cpp b/lib/Target/Mips/MipsTargetMachine.cpp
index ee28e2a122..a876f1c7f0 100644
--- a/lib/Target/Mips/MipsTargetMachine.cpp
+++ b/lib/Target/Mips/MipsTargetMachine.cpp
@@ -22,6 +22,7 @@
 #include "MipsSEISelLowering.h"
 #include "MipsSEISelDAGToDAG.h"
 #include "Mips16FrameLowering.h"
+#include "Mips16HardFloat.h"
 #include "Mips16InstrInfo.h"
 #include "Mips16ISelDAGToDAG.h"
 #include "Mips16ISelLowering.h"
@@ -156,6 +157,8 @@ void MipsPassConfig::addIRPasses() {
   TargetPassConfig::addIRPasses();
   if (getMipsSubtarget().os16())
     addPass(createMipsOs16(getMipsTargetMachine()));
+  if (getMipsSubtarget().inMips16HardFloat())
+    addPass(createMips16HardFloat(getMipsTargetMachine()));
 }
 // Install an instruction selector pass using
 // the ISelDag to gen Mips code.