efriedma added a comment.
For the "=x" thing I was talking about, try the following testcase:
void a() { struct S { unsigned x[4]; } z; asm volatile("%0":"=x"(z)); }
void a2() { struct S { unsigned x[8]; } z; asm volatile("%0":"=x"(z)); }
clang trunk gives "error: couldn't allocate output register for constraint 'x'"
in the backend for both functions. gcc prints "%xmm0" for the first, and
rejects the second; not exactly sure why it's rejecting the second, though. It
would be nice if both worked, although I guess it's okay if we print a
reasonable error message. Please add a testcase, at least.
================
Comment at: clang/test/CodeGen/x86_64-PR42672.c:3
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -USTRUCT -emit-llvm %s -o
- | FileCheck %s --check-prefix=CHECK-NOSTRUCT
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -DIMPOSSIBLE_ODD
-emit-llvm %s -o - 2> %t || true
+// RUN: grep "impossible constraint in asm" %t
----------------
You can prefix a command in a RUN line with "not" if you expect it to return a
non-zero error code. So you can write `not %clang_cc1 [...] 2>&1 | FileCheck
%s` or something like that.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D65234/new/
https://reviews.llvm.org/D65234
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