Commit Graph

2 Commits

Author SHA1 Message Date
Alexander Potapenko 57b87322ab [CodeGen]: fix error message for "=r" asm constraint
Summary:
Nico Weber reported that the following code:
  char buf[9];
  asm("" : "=r" (buf));

yields the "impossible constraint in asm: can't store struct into a register"
error message, although |buf| is not a struct (see
http://crbug.com/999160).

Make the error message more generic and add a test for it.
Also make sure other tests in x86_64-PR42672.c check for the full error
message.

Reviewers: eli.friedman, thakis

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66948

llvm-svn: 370444
2019-08-30 08:58:46 +00:00
Alexander Potapenko 1b5e38a6c9 [CodeGen]: don't treat structures returned in registers as memory inputs
Summary:
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.

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D65234

llvm-svn: 370335
2019-08-29 11:21:41 +00:00