llvm dev - Sep 2016 - Problem when using CloneFunctionInto()

Dear all,

I am very new to LLVM.  I run into a problem when changing the parameter
type and return type of a function. I do it in the following way:

     Step 1: create a new function type with new return type and new
parameter type

     Step 2: map old parameters to new parameters with new type, and add
the mapping to VMap

     Step3: for each old instruction in the function body which requires a
new type, I create a new instruction with new type, and add the mapping to
VMap

      Step4:using ClondFunctionInto(new_fun, old_fun, VMap, true, Returns)
to copy the body of the old function to the new function, with all values
in the VMap replaced with its new version.

Then I got the following error:

/llvm/lib/Transforms/Utils/ValueMapper.cpp:444: void
llvm::RemapInstruction(llvm::Instruction*, llvm::ValueToValueMapTy&,
llvm::RemapFlags, llvm::ValueMapTypeRemapper*, llvm::ValueMaterializer*):
Assertion `(Flags & RF_IgnoreMissingEntries) && "Referenced
value not in
value map!"' failed.

Is Step3 correct?  Since the document of CloneFunctionInto() said "Clone
OldFunc into NewFunc, transforming the old arguments into references to
VMap values." Could I also transform the old instructions in the function
body to new ones in the VMap?

Thank you very much :)

Sincerely,
Suhua
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