From e1ecc5b0dbb85157ba70c4366deca3418fa0890a Mon Sep 17 00:00:00 2001 From: Aaron Ballman Date: Wed, 3 Apr 2013 12:25:06 +0000 Subject: [PATCH] Second pass at addressing PR15351 by explicitly checking for AVX support when getting the host processor information. It emits a .byte sequence on GNUC compilers to work around lack of xgetbv support with older assemblers, and resolves a comment typo found in the previous patch. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178636 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Support/Host.cpp | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) diff --git a/lib/Support/Host.cpp b/lib/Support/Host.cpp index b9bbcb9322b..f91fb37e1da 100644 --- a/lib/Support/Host.cpp +++ b/lib/Support/Host.cpp @@ -112,6 +112,21 @@ static bool GetX86CpuIDAndInfo(unsigned value, unsigned *rEAX, #endif } +static bool OSHasAVXSupport() { +#if defined( __GNUC__ ) + // Check xgetbv; this uses a .byte sequence instead of the instruction + // directly because older assemblers do not include support for xgetbv and + // there is no easy way to conditionally compile based on the assembler used. + int rEAX, rEDX; + __asm__ (".byte 0x0f, 0x01, 0xd0" : "=a" (rEAX), "=d" (rEDX) : "c" (0)); +#elif defined(_MSC_VER) + unsigned long long rEAX = _xgetbv(_XCR_XFEATURE_ENABLED_MASK); +#else + int rEAX = 0; // Ensures we return false +#endif + return (rEAX & 6) == 6; +} + static void DetectX86FamilyModel(unsigned EAX, unsigned &Family, unsigned &Model) { Family = (EAX >> 8) & 0xf; // Bits 8 - 11 @@ -134,6 +149,10 @@ std::string sys::getHostCPUName() { DetectX86FamilyModel(EAX, Family, Model); bool HasSSE3 = (ECX & 0x1); + // If CPUID indicates support for XSAVE, XRESTORE and AVX, and XGETBV + // indicates that the AVX registers will be saved and restored on context + // switch, then we have full AVX support. + bool HasAVX = (ECX & ((1 << 28) | (1 << 27))) != 0 && OSHasAVXSupport(); GetX86CpuIDAndInfo(0x80000001, &EAX, &EBX, &ECX, &EDX); bool Em64T = (EDX >> 29) & 0x1; @@ -243,11 +262,15 @@ std::string sys::getHostCPUName() { case 42: // Intel Core i7 processor. All processors are manufactured // using the 32 nm process. case 45: - return "corei7-avx"; + // Not all Sandy Bridge processors support AVX (such as the Pentium + // versions instead of the i7 versions). + return HasAVX ? "corei7-avx" : "corei7"; // Ivy Bridge: case 58: - return "core-avx-i"; + // Not all Ivy Bridge processors support AVX (such as the Pentium + // versions instead of the i7 versions). + return HasAVX ? "core-avx-i" : "corei7"; case 28: // Most 45 nm Intel Atom processors case 38: // 45 nm Atom Lincroft -- 2.11.0