From 42b42489f92e98d0a58495dfb992073d99729a8b Mon Sep 17 00:00:00 2001 From: LLVM Packaging Team Date: Fri, 22 Dec 2017 10:17:30 +0000 Subject: [PATCH] clang-fix-cmpxchg8-detection-on-i386 libcxx atomic tests for old i386 fail with wrong Atomic inline width. cmpxchg8b instruction is required for 8 byte atomics that clang was assuming. Too bad _GCC_ATOMIC_LLONG_LOCK_FREE 2 isn't supported even with this change because llvm doesn't support unaligned atomic compare and exchange operation. Fallback calls to libatomic.so should handle long long lock free but clang can't tell program if libatomic is always lock free. Related bug: https://llvm.org/bugs/show_bug.cgi?id=19355 Gbp-Pq: Name clang-fix-cmpxchg8-detection-on-i386.patch --- clang/lib/Basic/Targets.cpp | 11 +++++++---- clang/test/Sema/atomic-ops.c | 2 +- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp index 036430c3..2b158c59 100644 --- a/clang/lib/Basic/Targets.cpp +++ b/clang/lib/Basic/Targets.cpp @@ -2622,7 +2622,10 @@ class X86TargetInfo : public TargetInfo { FP_SSE, FP_387 } FPMath = FP_Default; - +protected: + bool isCmpXChg8Supported() const { + return CPU >= CK_i586; + } public: X86TargetInfo(const llvm::Triple &Triple, const TargetOptions &) : TargetInfo(Triple) { @@ -2714,6 +2717,8 @@ public: // acceptable. // FIXME: This results in terrible diagnostics. Clang just says the CPU is // invalid without explaining *why*. + if (!isCmpXChg8Supported()) + MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 32; switch (CPU) { case CK_Generic: // No processor selected! @@ -3743,7 +3748,7 @@ void X86TargetInfo::getTargetDefines(const LangOptions &Opts, Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2"); Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4"); } - if (CPU >= CK_i586) + if (isCmpXChg8Supported()) Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_8"); } @@ -4022,8 +4027,6 @@ public: (1 << TargetInfo::LongDouble)); // x86-32 has atomics up to 8 bytes - // FIXME: Check that we actually have cmpxchg8b before setting - // MaxAtomicInlineWidth. (cmpxchg8b is an i586 instruction.) MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64; } BuiltinVaListKind getBuiltinVaListKind() const override { diff --git a/clang/test/Sema/atomic-ops.c b/clang/test/Sema/atomic-ops.c index 05836214..d4599649 100644 --- a/clang/test/Sema/atomic-ops.c +++ b/clang/test/Sema/atomic-ops.c @@ -14,7 +14,7 @@ _Static_assert(__GCC_ATOMIC_WCHAR_T_LOCK_FREE == 2, ""); _Static_assert(__GCC_ATOMIC_SHORT_LOCK_FREE == 2, ""); _Static_assert(__GCC_ATOMIC_INT_LOCK_FREE == 2, ""); _Static_assert(__GCC_ATOMIC_LONG_LOCK_FREE == 2, ""); -#ifdef __i386__ +#if defined(__i386__) _Static_assert(__GCC_ATOMIC_LLONG_LOCK_FREE == 1, ""); #else _Static_assert(__GCC_ATOMIC_LLONG_LOCK_FREE == 2, ""); -- 2.30.2