[clang][Interp] Fix parameter map when re-visiting function

[tbaeder]

Summary

'Params' is a member of the ByteCodeEmitter. We only added the
parameters the first time  we saw the function, so subsequent visits
didn't work if they had (and used) parameters.

Just do the work everytime we see a function.

[shafik]

LGTM

clang/lib/AST/Interp/ByteCodeEmitter.cpp

58

Where is Params used?

[tbaeder]

clang/lib/AST/Interp/ByteCodeEmitter.cpp

58

In ByteCodeExprGen.h to emit GetParam{,Ptr} ops (which take the paramter offset as an argument).

clang/lib/AST/Interp/ByteCodeEmitter.cpp

 using namespace clang;
 using namespace clang::interp;
 
 using APSInt = llvm::APSInt;
 using Error = llvm::Error;
 
 Expected<Function *>
 ByteCodeEmitter::compileFunc(const FunctionDecl *FuncDecl) {
-  // Create a handle over the emitted code.
-  Function *Func = P.getFunction(FuncDecl);
-  if (!Func) {
-    // Set up argument indices.
-    unsigned ParamOffset = 0;
-    SmallVector<PrimType, 8> ParamTypes;
-    llvm::DenseMap<unsigned, Function::ParamDescriptor> ParamDescriptors;
 
-    // If the return is not a primitive, a pointer to the storage where the
-    // value is initialized in is passed as the first argument. See 'RVO'
-    // elsewhere in the code.
-    QualType Ty = FuncDecl->getReturnType();
-    bool HasRVO = false;
-    if (!Ty->isVoidType() && !Ctx.classify(Ty)) {
-      HasRVO = true;
-      ParamTypes.push_back(PT_Ptr);
-      ParamOffset += align(primSize(PT_Ptr));
-    }
 
-    // If the function decl is a member decl, the next parameter is
-    // the 'this' pointer. This parameter is pop()ed from the
-    // InterpStack when calling the function.
-    bool HasThisPointer = false;
-    if (const auto *MD = dyn_cast<CXXMethodDecl>(FuncDecl);
-        MD && MD->isInstance()) {
-      HasThisPointer = true;
-      ParamTypes.push_back(PT_Ptr);
-      ParamOffset += align(primSize(PT_Ptr));
-    }
 
-    // Assign descriptors to all parameters.
-    // Composite objects are lowered to pointers.
-    for (const ParmVarDecl *PD : FuncDecl->parameters()) {
-      PrimType Ty = Ctx.classify(PD->getType()).value_or(PT_Ptr);
-      Descriptor *Desc = P.createDescriptor(PD, Ty);
-      ParamDescriptors.insert({ParamOffset, {Ty, Desc}});
-      Params.insert({PD, ParamOffset});
-      ParamOffset += align(primSize(Ty));
-      ParamTypes.push_back(Ty);
-    }
 
+  // Create a handle over the emitted code.
+  Function *Func = P.getFunction(FuncDecl);
+  if (!Func)
     Func =
         P.createFunction(FuncDecl, ParamOffset, std::move(ParamTypes),
                          std::move(ParamDescriptors), HasThisPointer, HasRVO);
-  }
 
   assert(Func);
   // For not-yet-defined functions, we only create a Function instance and
   // compile their body later.
   if (!FuncDecl->isDefined())
     return Func;
 
   // Compile the function body.

clang/test/AST/Interp/functions.cpp

 struct BodylessMemberFunction {
   constexpr int first() const {
     return second();
   }
   constexpr int second() const {
     return 1;
   }
 };
+
+constexpr int nyd(int m);
+constexpr int doit() { return nyd(10); }
+constexpr int nyd(int m) { return m; }
+static_assert(doit() == 10);