This is the first of three patches which creates stubs used for

Mips16/32 floating point interoperability.

When Mips16 code calls external functions that would normally have some
of its parameters or return values passed in floating point registers,
it needs (Mips32) helper functions to do this because while in Mips16 mode
there is no ability to access the floating point registers.

In Pic mode, this is done with a set of predefined functions in libc.
This case is already handled in llvm for Mips16.

In static relocation mode, for efficiency reasons, the compiler generates
stubs that the linker will use if it turns out that the external function
is a Mips32 function. (If it's Mips16, then it does not need the helper
stubs).

These stubs are identically named and the linker knows about these tricks
and will not create multiple copies and will delete them if they are not
needed.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181753 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 275 insertions, 0 deletions

diff --git a/lib/Target/Mips/Mips16HardFloat.cpp b/lib/Target/Mips/Mips16HardFloat.cpp
index 4d1e61b..304715a 100644
--- a/lib/Target/Mips/Mips16HardFloat.cpp
+++ b/lib/Target/Mips/Mips16HardFloat.cpp
@@ -18,6 +18,36 @@
 #include "llvm/Support/raw_ostream.h"
 #include <string>
 
+static void inlineAsmOut
+  (LLVMContext &C, StringRef AsmString, BasicBlock *BB ) {
+  std::vector<llvm::Type *> AsmArgTypes;
+  std::vector<llvm::Value*> AsmArgs;
+  llvm::FunctionType *AsmFTy =
+    llvm::FunctionType::get(Type::getVoidTy(C),
+                            AsmArgTypes, false);
+  llvm::InlineAsm *IA =
+    llvm::InlineAsm::get(AsmFTy, AsmString, "", true,
+                         /* IsAlignStack */ false,
+                         llvm::InlineAsm::AD_ATT);
+  CallInst::Create(IA, AsmArgs, "", BB);
+}
+
+namespace {
+
+class InlineAsmHelper {
+  LLVMContext &C;
+  BasicBlock *BB;
+public:
+  InlineAsmHelper(LLVMContext &C_, BasicBlock *BB_) :
+    C(C_), BB(BB_) {
+  }
+
+  void Out(StringRef AsmString) {
+    inlineAsmOut(C, AsmString, BB);
+  }
+
+};
+}
 //
 // Return types that matter for hard float are:
 // float, double, complex float, and complex double
@@ -52,6 +82,241 @@ static FPReturnVariant whichFPReturnVariant(Type *T) {
 }
 
 //
+// Parameter type that matter are float, (float, float), (float, double),
+// double, (double, double), (double, float)
+//
+enum FPParamVariant {
+  FSig, FFSig, FDSig,
+  DSig, DDSig, DFSig, NoSig
+};
+
+// which floating point parameter signature variant we are dealing with
+//
+typedef Type::TypeID TypeID;
+const Type::TypeID FloatTyID = Type::FloatTyID;
+const Type::TypeID DoubleTyID = Type::DoubleTyID;
+
+static FPParamVariant whichFPParamVariantNeeded(Function &F) {
+  switch (F.arg_size()) {
+  case 0:
+    return NoSig;
+  case 1:{
+    TypeID ArgTypeID = F.getFunctionType()->getParamType(0)->getTypeID();
+    switch (ArgTypeID) {
+    case FloatTyID:
+      return FSig;
+    case DoubleTyID:
+      return DSig;
+    default:
+      return NoSig;
+    }
+  }
+  default: {
+    TypeID ArgTypeID0 = F.getFunctionType()->getParamType(0)->getTypeID();
+    TypeID ArgTypeID1 = F.getFunctionType()->getParamType(1)->getTypeID();
+    switch(ArgTypeID0) {
+    case FloatTyID: {
+      switch (ArgTypeID1) {
+      case FloatTyID:
+        return FFSig;
+      case DoubleTyID:
+        return FDSig;
+      default:
+        return FSig;
+      }
+    }
+    case DoubleTyID: {
+      switch (ArgTypeID1) {
+      case FloatTyID:
+        return DFSig;
+      case DoubleTyID:
+        return DDSig;
+      default:
+        return DSig;
+      }
+    }
+    default:
+      return NoSig;
+    }
+  }
+  }
+  llvm_unreachable("can't get here");
+}
+
+// Figure out if we need float point based on the function parameters.
+// We need to move variables in and/or out of floating point
+// registers because of the ABI
+//
+static bool needsFPStubFromParams(Function &F) {
+  if (F.arg_size() >=1) {
+    Type *ArgType = F.getFunctionType()->getParamType(0);
+    switch (ArgType->getTypeID()) {
+      case Type::FloatTyID:
+      case Type::DoubleTyID:
+        return true;
+      default:
+        break;
+    }
+  }
+  return false;
+}
+
+static bool needsFPReturnHelper(Function &F) {
+  Type* RetType = F.getReturnType();
+  return whichFPReturnVariant(RetType) != NoFPRet;
+}
+
+static bool needsFPHelperFromSig(Function &F) {
+  return needsFPStubFromParams(F) || needsFPReturnHelper(F);
+}
+
+//
+// We swap between FP and Integer registers to allow Mips16 and Mips32 to
+// interoperate
+//
+
+void swapFPIntParams(FPParamVariant PV, Module *M, InlineAsmHelper &IAH,
+               bool LE, bool ToFP) {
+  //LLVMContext &Context = M->getContext();
+  std::string MI = ToFP? "mtc1 ": "mfc1 ";
+  switch (PV) {
+  case FSig:
+    IAH.Out(MI + "$$4,$$f12");
+    break;
+  case FFSig:
+    IAH.Out(MI +"$$4,$$f12");
+    IAH.Out(MI + "$$5,$$f14");
+    break;
+  case FDSig:
+    IAH.Out(MI + "$$4,$$f12");
+    if (LE) {
+      IAH.Out(MI + "$$6,$$f14");
+      IAH.Out(MI + "$$7,$$f15");
+    } else {
+      IAH.Out(MI + "$$7,$$f14");
+      IAH.Out(MI + "$$6,$$f15");
+    }
+    break;
+  case DSig:
+    if (LE) {
+      IAH.Out(MI + "$$4,$$f12");
+      IAH.Out(MI + "$$5,$$f13");
+    } else {
+      IAH.Out(MI + "$$5,$$f12");
+      IAH.Out(MI + "$$4,$$f13");
+    }
+    break;
+  case DDSig:
+    if (LE) {
+      IAH.Out(MI + "$$4,$$f12");
+      IAH.Out(MI + "$$5,$$f13");
+      IAH.Out(MI + "$$6,$$f14");
+      IAH.Out(MI + "$$7,$$f15");
+    } else {
+      IAH.Out(MI + "$$5,$$f12");
+      IAH.Out(MI + "$$4,$$f13");
+      IAH.Out(MI + "$$7,$$f14");
+      IAH.Out(MI + "$$6,$$f15");
+    }
+    break;
+  case DFSig:
+    if (LE) {
+      IAH.Out(MI + "$$4,$$f12");
+      IAH.Out(MI + "$$5,$$f13");
+    } else {
+      IAH.Out(MI + "$$5,$$f12");
+      IAH.Out(MI + "$$4,$$f13");
+    }
+    IAH.Out(MI + "$$6,$$f14");
+    break;
+  case NoSig:
+    return;
+  }
+}
+//
+// Make sure that we know we already need a stub for this function.
+// Having called needsFPHelperFromSig
+//
+void assureFPCallStub(Function &F, Module *M,  const MipsSubtarget &Subtarget){
+  // for now we only need them for static relocation
+  if (!Subtarget.getRelocationModel() == Reloc::PIC_)
+    return;
+  LLVMContext &Context = M->getContext();
+  bool LE = Subtarget.isLittle();
+  std::string Name = F.getName();
+  std::string SectionName = ".mips16.call.fp." + Name;
+  std::string StubName = "__call_stub_" + Name;
+  //
+  // see if we already have the stub
+  //
+  Function *FStub = M->getFunction(StubName);
+  if (FStub && !FStub->isDeclaration()) return;
+  FStub = Function::Create(F.getFunctionType(),
+                           Function::InternalLinkage, StubName, M);
+  FStub->addFnAttr("mips16_fp_stub");
+  FStub->addFnAttr(llvm::Attribute::Naked);
+  FStub->addFnAttr(llvm::Attribute::NoUnwind);
+  FStub->addFnAttr("nomips16");
+  FStub->setSection(SectionName);
+  BasicBlock *BB = BasicBlock::Create(Context, "entry", FStub);
+  InlineAsmHelper IAH(Context, BB);
+  FPReturnVariant RV = whichFPReturnVariant(FStub->getReturnType());
+  FPParamVariant PV = whichFPParamVariantNeeded(F);
+  swapFPIntParams(PV, M, IAH, LE, true);
+  if (RV != NoFPRet) {
+    IAH.Out("move $$18, $$31");
+    IAH.Out("jal " + Name);
+  } else {
+    IAH.Out("lui  $$25,%hi(" + Name + ")");
+    IAH.Out("addiu  $$25,$$25,%lo(" + Name + ")" );
+  }
+  switch (RV) {
+  case FRet:
+    IAH.Out("mfc1 $$2,$$f0");
+    break;
+  case DRet:
+    if (LE) {
+      IAH.Out("mfc1 $$2,$$f0");
+      IAH.Out("mfc1 $$3,$$f1");
+    } else {
+      IAH.Out("mfc1 $$3,$$f0");
+      IAH.Out("mfc1 $$2,$$f1");
+    }
+    break;
+  case CFRet:
+    if (LE) {
+    IAH.Out("mfc1 $$2,$$f0");
+    IAH.Out("mfc1 $$3,$$f2");
+    } else {
+      IAH.Out("mfc1 $$3,$$f0");
+      IAH.Out("mfc1 $$3,$$f2");
+    }
+    break;
+  case CDRet:
+    if (LE) {
+      IAH.Out("mfc1 $$4,$$f2");
+      IAH.Out("mfc1 $$5,$$f3");
+      IAH.Out("mfc1 $$2,$$f0");
+      IAH.Out("mfc1 $$3,$$f1");
+
+    } else {
+      IAH.Out("mfc1 $$5,$$f2");
+      IAH.Out("mfc1 $$4,$$f3");
+      IAH.Out("mfc1 $$3,$$f0");
+      IAH.Out("mfc1 $$2,$$f1");
+    }
+    break;
+  case NoFPRet:
+    break;
+  }
+  if (RV != NoFPRet)
+    IAH.Out("jr $$18");
+  else
+    IAH.Out("jr $$25");
+  new UnreachableInst(Context, BB);
+}
+
+//
 // Returns of float, double and complex need to be handled with a helper
 // function. The "AndCal" part is coming in a later patch.
 //
@@ -96,6 +361,16 @@ static bool fixupFPReturnAndCall
                            Attribute::ReadNone);
         Value *F = (M->getOrInsertFunction(Name, A, MyVoid, T, NULL));
         CallInst::Create(F, Params, "", &Inst );
+      } else if (const CallInst *CI = dyn_cast<CallInst>(I)) {
+          // pic mode calls are handled by already defined
+          // helper functions
+          if (Subtarget.getRelocationModel() != Reloc::PIC_ ) {
+            Function *F_ =  CI->getCalledFunction();
+            if (F_ && needsFPHelperFromSig(*F_)) {
+              assureFPCallStub(*F_, M, Subtarget);
+              Modified=true;
+            }
+          }
       }
     }
   return Modified;