[PATCH] D24597: [cpu-detection] Copy simplified version of get_cpuid_max to remove dependency to clang's implementation
Alina Sbirlea via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 14 19:33:19 PDT 2016
asbirlea created this revision.
asbirlea added reviewers: echristo, joerg.
asbirlea added a subscriber: llvm-commits.
Herald added a subscriber: mehdi_amini.
Attempting to fix PR30384.
Take the same approach as in compiler_rt and add a simplified version of __get_cpuid_max.
Including cpuid.h is no longer needed.
https://reviews.llvm.org/D24597
Files:
lib/Support/Host.cpp
Index: lib/Support/Host.cpp
===================================================================
--- lib/Support/Host.cpp
+++ lib/Support/Host.cpp
@@ -73,10 +73,6 @@
#if defined(__i386__) || defined(_M_IX86) || \
defined(__x86_64__) || defined(_M_X64)
-#if defined(__GNUC__) || defined(__clang__)
-#include <cpuid.h>
-#endif
-
enum VendorSignatures {
SIG_INTEL = 0x756e6547 /* Genu */,
SIG_AMD = 0x68747541 /* Auth */
@@ -173,6 +169,38 @@
FEATURE_EM64T
};
+// The check below for i386 was copied from clang's cpuid.h (__get_cpuid_max).
+// Check motivated by bug reports for OpenSSL crashing on CPUs without CPUID
+// support. Consequently, for i386, the presence of CPUID is checked first
+// via the corresponding eflags bit.
+static bool isCpuIdSupported() {
+#if defined(__GNUC__) || defined(__clang__)
+#if defined(__i386__)
+ int __cpuid_supported;
+ __asm__(" pushfl\n"
+ " popl %%eax\n"
+ " movl %%eax,%%ecx\n"
+ " xorl $0x00200000,%%eax\n"
+ " pushl %%eax\n"
+ " popfl\n"
+ " pushfl\n"
+ " popl %%eax\n"
+ " movl $0,%0\n"
+ " cmpl %%eax,%%ecx\n"
+ " je 1f\n"
+ " movl $1,%0\n"
+ "1:"
+ : "=r"(__cpuid_supported)
+ :
+ : "eax", "ecx");
+ if (!__cpuid_supported)
+ return false;
+#endif
+ return true;
+#endif
+ return true;
+}
+
/// getX86CpuIDAndInfo - Execute the specified cpuid and return the 4 values in
/// the specified arguments. If we can't run cpuid on the host, return true.
static bool getX86CpuIDAndInfo(unsigned value, unsigned *rEAX, unsigned *rEBX,
@@ -748,7 +776,8 @@
//FIXME: include cpuid.h from clang or copy __get_cpuid_max here
// and simplify it to not invoke __cpuid (like cpu_model.c in
// compiler-rt/lib/builtins/cpu_model.c?
- if(!__get_cpuid_max(0, &Vendor))
+ // Opting for the second option.
+ if(!isCpuIdSupported())
return "generic";
#endif
if (getX86CpuIDAndInfo(0, &MaxLeaf, &Vendor, &ECX, &EDX))
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