round 2 of denormal handling changes - detect DAZ support at runtime, and use accordingly. move all FPU feature detection into PBD::FPU

git-svn-id: svn://localhost/ardour2/trunk@1939 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 92 insertions, 0 deletions

diff --git a/libs/pbd/fpu.cc b/libs/pbd/fpu.cc
new file mode 100644
index 0000000000..ae69b62e8d
--- /dev/null
+++ b/libs/pbd/fpu.cc
@@ -0,0 +1,92 @@
+#define _XOPEN_SOURCE 600
+#include <stdlib.h>
+#include <stdint.h>
+
+#include <pbd/fpu.h>
+#include <pbd/error.h>
+
+#include "i18n.h"
+
+using namespace PBD;
+using namespace std;
+
+FPU::FPU ()
+{
+	unsigned long cpuflags = 0;
+
+	_flags = Flags (0);
+
+#ifndef ARCH_X86
+	return;
+#endif
+	
+#ifndef USE_X86_64_ASM
+	asm volatile (
+		"mov $1, %%eax\n"
+		"pushl %%ebx\n"
+		"cpuid\n"
+		"movl %%edx, %0\n"
+		"popl %%ebx\n"
+		: "=r" (cpuflags)
+		: 
+		: "%eax", "%ecx", "%edx", "memory"
+		);
+	
+#else
+	
+	asm volatile (
+		"pushq %%rbx\n"
+		"movq $1, %%rax\n"
+		"cpuid\n"
+		"movq %%rdx, %0\n"
+		"popq %%rbx\n"
+		: "=r" (cpuflags)
+		: 
+		: "%rax", "%rcx", "%rdx", "memory"
+		);
+
+#endif /* USE_X86_64_ASM */
+	
+	if (cpuflags & (1<<25)) {
+		_flags = Flags (_flags | (HasSSE|HasFlushToZero));
+	}
+
+	if (cpuflags & (1<<26)) {
+		_flags = Flags (_flags | HasSSE2);
+	}
+
+	if (cpuflags & (1 << 24)) {
+		
+		char* fxbuf = 0;
+		
+		if (posix_memalign ((void**)&fxbuf, 16, 512)) {
+			error << _("cannot allocate 16 byte aligned buffer for h/w feature detection") << endmsg;
+		} else {
+			
+			asm volatile (
+				"fxsave (%0)"
+				:
+				: "r" (fxbuf)
+				: "memory"
+				);
+			
+			uint32_t mxcsr_mask = *((uint32_t*) &fxbuf[28]);
+			
+			/* if the mask is zero, set its default value (from intel specs) */
+			
+			if (mxcsr_mask == 0) {
+				mxcsr_mask = 0xffbf;
+			}
+			
+			if (mxcsr_mask & (1<<6)) {
+				_flags = Flags (_flags | HasDenormalsAreZero);
+			} 
+
+			free (fxbuf);
+		}
+	}
+}			
+
+FPU::~FPU ()
+{
+}