[compiler-rt] r339575 - [sanitizer] Remove st(X) from the clobber list in 32-bit x86 atomics

[Kostya Kortchinsky via llvm-commits]

Author: cryptoad
Date: Mon Aug 13 08:01:24 2018
New Revision: 339575

URL: http://llvm.org/viewvc/llvm-project?rev=339575&view=rev
Log:
[sanitizer] Remove st(X) from the clobber list in 32-bit x86 atomics

Summary:
When compiling with `WERROR=ON` & a recent clang, having the `st(?)` registers
in the clobber list produces a fatal error (except `st(7)` for some reason):
```
.../sanitizer_common/sanitizer_atomic_clang_x86.h:98:9: error: inline asm clobber list contains reserved registers: ST0, ST1, ST2, ST3, ST4, ST5, ST6 [-Werror,-Winline-asm]
        "movq %1, %%mm0;"  // Use mmx reg for 64-bit atomic moves
        ^
<inline asm>:1:1: note: instantiated into assembly here
        movq 8(%esp), %mm0;movq %mm0, (%esi);emms;
^
.../sanitizer_common/sanitizer_atomic_clang_x86.h:98:9: note: Reserved registers on the clobber list may not be preserved across the asm statement, and clobbering them may lead to undefined behaviour.
        "movq %1, %%mm0;"  // Use mmx reg for 64-bit atomic moves
        ^
<inline asm>:1:1: note: instantiated into assembly here
        movq 8(%esp), %mm0;movq %mm0, (%esi);emms;
^
```
As far as I can tell, they were in there due to the use of the `emms`
instruction, but removing the clobber doesn't appear to have a functional
impact. I am unsure if there is a better way to address this.

Reviewers: eugenis, vitalybuka

Reviewed By: vitalybuka

Subscribers: kubamracek, delcypher, jfb, llvm-commits, #sanitizers

Differential Revision: https://reviews.llvm.org/D50562

Modified:
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_clang_x86.h

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_clang_x86.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_clang_x86.h?rev=339575&r1=339574&r2=339575&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_clang_x86.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_clang_x86.h Mon Aug 13 08:01:24 2018
@@ -61,8 +61,7 @@ INLINE typename T::Type atomic_load(
         "emms;"            // Empty mmx state/Reset FP regs
         : "=m" (v)
         : "m" (a->val_dont_use)
-        : // mark the FP stack and mmx registers as clobbered
-          "st", "st(1)", "st(2)", "st(3)", "st(4)", "st(5)", "st(6)", "st(7)",
+        : // mark the mmx registers as clobbered
 #ifdef __MMX__
           "mm0", "mm1", "mm2", "mm3", "mm4", "mm5", "mm6", "mm7",
 #endif  // #ifdef __MMX__
@@ -100,8 +99,7 @@ INLINE void atomic_store(volatile T *a,
         "emms;"            // Empty mmx state/Reset FP regs
         : "=m" (a->val_dont_use)
         : "m" (v)
-        : // mark the FP stack and mmx registers as clobbered
-          "st", "st(1)", "st(2)", "st(3)", "st(4)", "st(5)", "st(6)", "st(7)",
+        : // mark the mmx registers as clobbered
 #ifdef __MMX__
           "mm0", "mm1", "mm2", "mm3", "mm4", "mm5", "mm6", "mm7",
 #endif  // #ifdef __MMX__