[PATCH] eal/x86: use cpuid builtin

[Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>]

GCC does have the __get_cpuid_count builtin which checks for maximum
supported leaf, but implementations differ between CLANG and GCC.

This change provides an implementation compatible with both GCC and
CLANG 3.4+.

Signed-off-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>
---
 lib/librte_eal/common/arch/x86/rte_cpuflags.c | 40 ++++++---------------------
 1 file changed, 8 insertions(+), 32 deletions(-)

diff --git a/lib/librte_eal/common/arch/x86/rte_cpuflags.c b/lib/librte_eal/common/arch/x86/rte_cpuflags.c
index 0138257..7d4a0fe 100644
--- a/lib/librte_eal/common/arch/x86/rte_cpuflags.c
+++ b/lib/librte_eal/common/arch/x86/rte_cpuflags.c
@@ -36,6 +36,7 @@
 #include <stdio.h>
 #include <errno.h>
 #include <stdint.h>
+#include <cpuid.h>
 
 enum cpu_register_t {
 	RTE_REG_EAX = 0,
@@ -156,38 +157,12 @@ const struct feature_entry rte_cpu_feature_table[] = {
 	FEAT_DEF(INVTSC, 0x80000007, 0, RTE_REG_EDX,  8)
 };
 
-/*
- * Execute CPUID instruction and get contents of a specific register
- *
- * This function, when compiled with GCC, will generate architecture-neutral
- * code, as per GCC manual.
- */
-static void
-rte_cpu_get_features(uint32_t leaf, uint32_t subleaf, cpuid_registers_t out)
-{
-#if defined(__i386__) && defined(__PIC__)
-	/* %ebx is a forbidden register if we compile with -fPIC or -fPIE */
-	asm volatile("movl %%ebx,%0 ; cpuid ; xchgl %%ebx,%0"
-		 : "=r" (out[RTE_REG_EBX]),
-		   "=a" (out[RTE_REG_EAX]),
-		   "=c" (out[RTE_REG_ECX]),
-		   "=d" (out[RTE_REG_EDX])
-		 : "a" (leaf), "c" (subleaf));
-#else
-	asm volatile("cpuid"
-		 : "=a" (out[RTE_REG_EAX]),
-		   "=b" (out[RTE_REG_EBX]),
-		   "=c" (out[RTE_REG_ECX]),
-		   "=d" (out[RTE_REG_EDX])
-		 : "a" (leaf), "c" (subleaf));
-#endif
-}
-
 int
 rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
 {
 	const struct feature_entry *feat;
 	cpuid_registers_t regs;
+	unsigned int maxleaf;
 
 	if (feature >= RTE_CPUFLAG_NUMFLAGS)
 		/* Flag does not match anything in the feature tables */
@@ -199,13 +174,14 @@ rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
 		/* This entry in the table wasn't filled out! */
 		return -EFAULT;
 
-	rte_cpu_get_features(feat->leaf & 0xffff0000, 0, regs);
-	if (((regs[RTE_REG_EAX] ^ feat->leaf) & 0xffff0000) ||
-	      regs[RTE_REG_EAX] < feat->leaf)
+	maxleaf = __get_cpuid_max(feat->leaf & 0x80000000, NULL);
+
+	if (maxleaf < feat->leaf)
 		return 0;
 
-	/* get the cpuid leaf containing the desired feature */
-	rte_cpu_get_features(feat->leaf, feat->subleaf, regs);
+	 __cpuid_count(feat->leaf, feat->subleaf,
+			 regs[RTE_REG_EAX], regs[RTE_REG_EBX],
+			 regs[RTE_REG_ECX], regs[RTE_REG_EDX]);
 
 	/* check if the feature is enabled */
 	return (regs[feat->reg] >> feat->bit) & 1;
-- 
2.9.5