|No such thing as a small change|
A first reaction (I'm getting punchy at this point in time.). If you use LLVM as just an alternative C compiler, then as a part of the process of compiling perl -- unchanged -- it will compile whatever code/functions/source file(s) that constitute the current "runloop" (ostensibly runops_standard in run.c).
One of the possible variations of using LLVM in this mode, is that it (clang) can output .bc (bitcode) files, that can later be linked together -- using the LLVM linker -- to produce a native executable. What's more, is that the LLVM linker is quite happy to accept some "object files" that are in .bc format, and some that are in the normal .obj/.o format, and link them together and produce a (normal) platform dependent executable.
It is also possible, to have clang produce LLVM IF in text form.
So, in theory, if we ran (something like; there's a lot of documentation) clang --emit-text run.c -O run.o and then inspected run.o in a text editor, it would tell us exactly what the IF looks like for that source file.
And that IF, would (in its binary form), be combinable -- with all the other normal object files produced using gcc or cl.exe -- using the LLVM linker, to produce a working, native compiled executable.
That is not a direct answer to your question, but the point is that (as a starting point), it is possible to build a working executable, by substituting any individual clang-compiled-to-bitcode-source-file, for the native compiled objct file from that source, and combine it with all the other GGC/CL produced object files, and the LLVM linker will happily combine them into into a native executable.
Thus, to see what the LLVM IF look like, for any given source file, you only need to use clang to compile that individual source file to its text representation. You don't gain any performance, but you do get to see what LLVM IF looks like.
I'll attempt to get back to you with a specific answer to your question, but given that my LLVM installation if 2 years old, and my primary perl installation about the same, It'll take a couple of days to get caught up.
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