[AArch64, inline-asm] Improve diagnostic that is printed when the size of a

variable that has regiser constraint "r" is not 64-bit.

General register operands are output using 64-bit "x" register names, regardless
of the size of the variable, unless the asm operand is prefixed with the "%w"
modifier. This surprises and confuses many users who aren't familiar with
aarch64 inline assembly rules.

With this commit, a note and fixit hint are printed which tell the users that
they need modifier "%w" in order to output a "w" register instead of an "x"
register.

<rdar://problem/12764785>

llvm-svn: 216260

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/test/Sema/inline-asm-validate.c b/clang/test/Sema/inline-asm-validate.c
index 6fa760c8092..73335e76cd8 100644
--- a/clang/test/Sema/inline-asm-validate.c
+++ b/clang/test/Sema/inline-asm-validate.c
@@ -3,6 +3,6 @@
 unsigned t, r, *p;
 
 int foo (void) {
-  __asm__ __volatile__( "stxr   %w[_t], %[_r], [%[_p]]" : [_t] "=&r" (t) : [_p] "p" (p), [_r] "r" (r) : "memory"); // expected-warning{{value size does not match register size specified by the constraint and modifier}}
+  __asm__ __volatile__( "stxr   %w[_t], %[_r], [%[_p]]" : [_t] "=&r" (t) : [_p] "p" (p), [_r] "r" (r) : "memory"); // expected-warning{{value size does not match register size specified by the constraint and modifier}} expected-note {{use constraint modifier "w"}}
   return 1;
 }