[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

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index 90974345bc3..707db04a892 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -2326,7 +2326,7 @@ void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
         const Expr *OutExpr = S.getOutputExpr(i);
         CGM.Error(
             OutExpr->getExprLoc(),
-            "impossible constraint in asm: can't store struct into a register");
+            "impossible constraint in asm: can't store value into a register");
         return;
       }
       Dest = MakeAddrLValue(A, Ty);