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[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
This commit is contained in:
Alexander Potapenko 2019-08-30 08:58:46 +00:00
parent fd66c8bf07
commit 57b87322ab
2 changed files with 18 additions and 3 deletions
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2
clang/lib/CodeGen/CGStmt.cpp
View File

@ -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);

19
clang/test/CodeGen/x86_64-PR42672.c
View File

@ -4,6 +4,7 @@
// RUN: not %clang_cc1 -triple=x86_64-unknown-linux-gnu -DIMPOSSIBLE_BIG -emit-llvm %s -o - 2>&1 | FileCheck %s --check-prefix=CHECK-IMPOSSIBLE_BIG
// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -DPOSSIBLE_X -emit-llvm %s -o - 2>&1 | FileCheck %s --check-prefix=CHECK-X
// RUN: not %clang_cc1 -triple=x86_64-unknown-linux-gnu -DIMPOSSIBLE_X -emit-llvm %s -o - 2>&1 | FileCheck %s --check-prefix=CHECK-IMPOSSIBLE_X
// RUN: not %clang_cc1 -triple=x86_64-unknown-linux-gnu -DIMPOSSIBLE_9BYTES -emit-llvm %s -o - 2>&1 | FileCheck %s --check-prefix=CHECK-IMPOSSIBLE_9BYTES
// Make sure Clang doesn't treat |lockval| as asm input.
void _raw_spin_lock(void) {
@ -57,7 +58,7 @@ void odd_struct(void) {
: "=r"(str));
#endif
}
// CHECK-IMPOSSIBLE_ODD: impossible constraint in asm
// CHECK-IMPOSSIBLE_ODD: impossible constraint in asm: can't store value into a register
// Check Clang reports an error if attempting to return a big structure via a register.
void big_struct(void) {
@ -69,7 +70,7 @@ void big_struct(void) {
: "=r"(str));
#endif
}
// CHECK-IMPOSSIBLE_BIG: impossible constraint in asm
// CHECK-IMPOSSIBLE_BIG: impossible constraint in asm: can't store value into a register
// Clang is able to emit LLVM IR for an 16-byte structure.
void x_constraint_fit() {
@ -100,3 +101,17 @@ void x_constraint_nofit() {
}
// CHECK-IMPOSSIBLE_X: invalid output size for constraint
// http://crbug.com/999160
// Clang used to report the following message:
// "impossible constraint in asm: can't store struct into a register"
// for the assembly directive below, although there's no struct.
void crbug_999160_regtest() {
#ifdef IMPOSSIBLE_9BYTES
char buf[9];
asm(""
: "=r"(buf));
#endif
}
// CHECK-IMPOSSIBLE_9BYTES: impossible constraint in asm: can't store value into a register