[Zion] Enable SSE instructions at the start of boot.

These aren't ready to be used yet as we need to save them on task
switch.

zion/common/cpu.cpp

@@ -0,0 +1,30 @@
+#include "common/cpu.h"
+
+#include <cpuid.h>
+
+#include "debug/debug.h"
+
+void ProbeCpuAndEnableFeatures() {
+  dbgln("CPUID");
+  uint32_t eax, ebx, ecx, edx;
+  __get_cpuid(1, &eax, &ebx, &ecx, &edx);
+
+  if (!(edx & (0x3 << 25))) {
+    panic("SSE & SSE2 not available.");
+  }
+
+  if (!(ecx & (0x1 | (0x1 << 9)))) {
+    panic("SSE3, SSSE3 not available.");
+  }
+
+  dbgln("Setting SSE");
+  asm volatile(
+      "mov %%cr0, %%rax;"
+      "and $0xFFFB, %%ax;"  // Clear EM
+      "or $0x2, %%ax;"      // Set MP
+      "mov %%rax, %%cr0;"
+      "mov %%cr4, %%rax;"
+      "or $0x600, %%ax;"  // Set OSFXSR, OSXMMEXCPT
+      "mov %%rax, %%cr4;" ::
+          : "rax");
+}

zion/common/cpu.h

@@ -0,0 +1,3 @@
+#pragma once
+
+void ProbeCpuAndEnableFeatures();