[PATCH] D65234: [CodeGen]: don't treat structures returned in registers as memory inputs

[Alexander Potapenko via Phabricator via cfe-commits]

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The "=r" output constraint for a structure variable passed to inline asm
shouldn't be converted to "=*r", as this changes the asm directive
semantics and prevents DSE optimizations.
Instead, preserve the constraints and return such structures as integers
of corresponding size, which are converted back to structures when
storing the result.

Fixes PR42672.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D65234

Files:
  clang/lib/CodeGen/CGStmt.cpp
  clang/test/CodeGen/PR42672.c
  clang/test/CodeGen/asm-attrs.c

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