d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

For now, revert upstream clang r323281 (by Wei Mi):

Browse Source 
Adjust MaxAtomicInlineWidth for i386/i486 targets.

  This is to fix the bug reported in
  https://bugs.llvm.org/show_bug.cgi?id=34347#c6.  Currently, all
  MaxAtomicInlineWidth of x86-32 targets are set to 64.  However, i386
  doesn't support any cmpxchg related instructions. i486 only supports
  cmpxchg.  So in this patch MaxAtomicInlineWidth is reset as follows:
  For i386, the MaxAtomicInlineWidth should be 0 because no cmpxchg is
  supported.  For i486, the MaxAtomicInlineWidth should be 32 because
  it supports cmpxchg.  For others 32 bits x86 cpu, the
  MaxAtomicInlineWidth should be 64 because of cmpxchg8b.

  Differential Revision: https://reviews.llvm.org/D42154

This should fix buildworld on i386, because of our system libraries
missing __atomic_load_8, and possibly other 64 bit atomic functions, for
that architecture.

We should really fix that at some point, but since we have been actually
using cmpxchg8b for years now, it does not seem to matter much...
This commit is contained in:
dim 2018-08-17 16:25:59 +00:00
parent b4e507b00b
commit ef28bd8d33
1 changed files with 3 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
contrib/llvm/tools/clang/lib/Basic/Targets/X86.h
View File

@ -350,11 +350,9 @@ public:
(1 << TargetInfo::LongDouble)); (1 << TargetInfo::LongDouble));
// x86-32 has atomics up to 8 bytes // x86-32 has atomics up to 8 bytes
CPUKind Kind = getCPUKind(Opts.CPU); // FIXME: Check that we actually have cmpxchg8b before setting
if (Kind >= CK_i586 || Kind == CK_Generic) // MaxAtomicInlineWidth. (cmpxchg8b is an i586 instruction.)
MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64; MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
else if (Kind >= CK_i486)
MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 32;
} }
BuiltinVaListKind getBuiltinVaListKind() const override { BuiltinVaListKind getBuiltinVaListKind() const override {