https://bugs.llvm.org/show_bug.cgi?id=37400
Bug ID: 37400
Summary: MSVC and Clang use different values for _MM_HINT
constants; Windows SDK hardcodes MSVC values
Product: clang
Version: 6.0
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Headers
Assignee: unassignedclangb...@nondot.org
Reporter: fabi...@radgametools.com
CC: llvm-bugs@lists.llvm.org
With clang-cl 6.0:
// ---- begin
#include <emmintrin.h>
#include <Windows.h> // <--- only with this present!
void f(const void *p)
{
_mm_prefetch((const char *)p, _MM_HINT_T0);
}
// ---- end
"clang-cl -c -O2 -FA prefetch.cpp" yields (only relevant parts):
# ---- begin
"?f@@YAXPEBX@Z": # @"\01?f@@YAXPEBX@Z"
# %bb.0:
prefetcht2 (%rcx)
retq
# ---- end
...huh? Some grepping later, it turns out that "um\winnt.h" in the Windows SDK
10.0.16299.0 (and presumably other versions as well, but I didn't check)
contains this:
C:\Program Files (x86)\Windows Kits\10\Include\10.0.16299.0>rg MM_HINT_T0
um\winnt.h
3266:#define _MM_HINT_T0 1
3296:#define PF_TEMPORAL_LEVEL_1 _MM_HINT_T0
7349:#define _MM_HINT_T0 1
7366:#define PF_TEMPORAL_LEVEL_1 _MM_HINT_T0
and indeed, the MSVC version of xmmintrin.h has _MM_HINT_T0 #defined to 1.
Long story short, for any translation unit that includes Windows.h,
_MM_HINT_* end up re-#defined to MSVC-specific values, which produce the wrong
instructions with clang-cl.
If the goal is to make clang-cl be able to compile apps using unmodified
Windows headers, then Clang needs to use the same values for _MM_HINT_* as MSVC
does. (Presumably with some remapping done in the frontend.) Sigh.
--
You are receiving this mail because:
You are on the CC list for the bug._______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
