[cfe-dev] [CGCall] Mapping elements of CallArgList to parameter declarations

Reid Kleckner rnk at google.com
Thu Aug 14 11:43:15 PDT 2014

I just thought of something. Try threading the function or block decl
through EmitCallArgs.  EmitCallArgs is responsible for evaluating all
user-written Exprs, which should have a one-to-one correspondence with
ParmVarDecls on the function or block decl.

On Thu, Aug 14, 2014 at 11:26 AM, Alexey Samsonov <vonosmas at gmail.com>

> Hi,
> I need to access declarations of function parameters when I emit a call to
> this function. Namely, if certain function parameters are declared to be
> nonnull (by __attribute__((nonnull))), I can add corresponding attributes
> to the call site and emit a runtime check verifying that call arguments are
> indeed nonnull.
> This turns out to be unexpectedly hard: when we emit a call
> (CodeGenFunction::EmitCall), we have the following information:
>   1) CGFunctionInfo, which is essentially a vector describing types/ABI
> kinds of call arguments (of LLVM IR function).
>   2) CallArgList, which has the same size as CGFunctionInfo and contains
> RValues - actual call arguments.
>   3) (optional) Decl of a callee.
> However, we don't have a mapping that would tell us which elements of
> CGFunctionInfo/CallArgList correspond to ParmVarDecl in a callee Decl
> (there can be different kinds of implicit arguments, like "this", or VTT,
> and their position in CallArgList is not trivially deducible).
> Am I missing something obvious? Or this task indeed can't be done without
> significant refactoring of CGCall logic? Thanks.
> --
> Alexey Samsonov
> vonosmas at gmail.com
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