[libc] Use '+' constraint on inline assembly

[abrachet]

Summary

As suggested by @mcgrathr in D118099

[abrachet]

@nathanchance could you take a look if this fixes the problem from https://github.com/llvm/llvm-project/issues/53391 for you? I was not able to reproduce this error after the workaround

[nathanchance]

In D119978#3327553, @abrachet wrote:

@nathanchance could you take a look if this fixes the problem from https://github.com/llvm/llvm-project/issues/53391 for you? I was not able to reproduce this error after the workaround

Yes, it does. Thanks a lot for the quick fix!

libc/src/math/x86_64/cos.cpp

 //===-- Implementation of the cos function for x86_64 ---------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/math/cos.h"
 #include "src/__support/common.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(double, cos, (double x)) {
-  double result;
-  __asm__ __volatile__("fcos" : "=t"(result) : "f"(x) : "cc");
-  return result;
+  __asm__ __volatile__("fcos" : "+t"(x));
+  return x;
 }
 
 } // namespace __llvm_libc

libc/src/math/x86_64/sin.cpp

 //===-- Implementation of the sin function for x86_64 ---------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/math/sin.h"
 #include "src/__support/common.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(double, sin, (double x)) {
-  double result;
-  __asm__ __volatile__("fsin" : "=t"(result) : "f"(x) : "cc");
-  return result;
+  __asm__ __volatile__("fsin" : "+t"(x));
+  return x;
 }
 
 } // namespace __llvm_libc

libc/src/math/x86_64/tan.cpp

 //===-- Implementation of the tan function for x86_64 ---------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/math/tan.h"
 #include "src/__support/common.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(double, tan, (double x)) {
   double result;
-  double one;
   // The fptan instruction pushes the number 1 on to the FP stack after
   // computing tan. So, we read out the one before popping the actual result.
-  __asm__ __volatile__("fptan" : "=t"(one) : "f"(x) : "cc");
+  __asm__ __volatile__("fptan" : "+t"(x));
   __asm__ __volatile__("fstpl %0" : "=m"(result));
   return result;
 }
 
 } // namespace __llvm_libc