[PATCH] D85614: [TRE] Reland: allow TRE for non-capturing calls.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp:600
+                       CI->getArgOperand(OpndIdx),
+                       /*SrcAlign*/ Alignment, Size);
+
----------------
This is the right direction, but I'm not sure it does the right thing in general.

In particular, it's possible that `CI->getArgOperand(OpndIdx)` points to one of the allocas created by createTempForByValOperand(); if it does, then this copy might be clobbering data you need for subsequent copies.  Again, consider the `void dostuff(A arg, Arg b) { dostuff(b, a); }` case.

This is why the general procedure I outlined has an extra step: we copy the temporary allocas to the original byval arguments, and use the byval arguments as the operands to the PHI.  That way, `CI->getArgOperand(OpndIdx)` never points to one of the allocas allocated by createTempForByValOperand.


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  https://reviews.llvm.org/D85614/new/

https://reviews.llvm.org/D85614