Fix the CPU feature detection.

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 68d2c05edc526626976de2c7e5c6a7a0f6d6a8f6..f3ce4b9420dd36ecdfaf017b34bdf32af7fb9eb3 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -63,98 +63,32 @@ void CpuFeatures::Probe() {
     return;  // No features if we might serialize.
   }
 
-  const int kBufferSize = 4 * KB;
-  VirtualMemory* memory = new VirtualMemory(kBufferSize);
-  if (!memory->IsReserved()) {
-    delete memory;
-    return;
+  uint64_t probed_features = 0;
+  CPU cpu;
+  if (cpu.has_sse41()) {
+    probed_features |= static_cast<uint64_t>(1) << SSE4_1;
   }
-  ASSERT(memory->size() >= static_cast<size_t>(kBufferSize));
-  if (!memory->Commit(memory->address(), kBufferSize, true/*executable*/)) {
-    delete memory;
-    return;
+  if (cpu.has_sse3()) {
+    probed_features |= static_cast<uint64_t>(1) << SSE3;
   }
 
-  Assembler assm(NULL, memory->address(), kBufferSize);
-  Label cpuid, done;
-#define __ assm.
-  // Save old rsp, since we are going to modify the stack.
-  __ push(rbp);
-  __ pushfq();
-  __ push(rdi);
-  __ push(rcx);
-  __ push(rbx);
-  __ movq(rbp, rsp);
-
-  // If we can modify bit 21 of the EFLAGS register, then CPUID is supported.
-  __ pushfq();
-  __ pop(rax);
-  __ movq(rdx, rax);
-  __ xor_(rax, Immediate(0x200000));  // Flip bit 21.
-  __ push(rax);
-  __ popfq();
-  __ pushfq();
-  __ pop(rax);
-  __ xor_(rax, rdx);  // Different if CPUID is supported.
-  __ j(not_zero, &cpuid);
-
-  // CPUID not supported. Clear the supported features in rax.
-  __ xor_(rax, rax);
-  __ jmp(&done);
-
-  // Invoke CPUID with 1 in eax to get feature information in
-  // ecx:edx. Temporarily enable CPUID support because we know it's
-  // safe here.
-  __ bind(&cpuid);
-  __ movl(rax, Immediate(1));
-  supported_ = kDefaultCpuFeatures | (1 << CPUID);
-  { CpuFeatureScope fscope(&assm, CPUID);
-    __ cpuid();
-    // Move the result from ecx:edx to rdi.
-    __ movl(rdi, rdx);  // Zero-extended to 64 bits.
-    __ shl(rcx, Immediate(32));
-    __ or_(rdi, rcx);
-
-    // Get the sahf supported flag, from CPUID(0x80000001)
-    __ movq(rax, 0x80000001, RelocInfo::NONE64);
-    __ cpuid();
+  // SSE2 must be available on every x64 CPU.
+  ASSERT(cpu.has_sse2());
+  probed_features |= static_cast<uint64_t>(1) << SSE2;
+
+  // CMOD must be available on every x64 CPU.
+  ASSERT(cpu.has_cmov());
+  probed_features |= static_cast<uint64_t>(1) << CMOV;
+
+  // SAHF is not generally available in long mode.
+  if (cpu.has_sahf()) {
+    probed_features |= static_cast<uint64_t>(1) << SAHF;
   }
-  supported_ = kDefaultCpuFeatures;
 
-  // Put the CPU flags in rax.
-  // rax = (rcx & 1) | (rdi & ~1) | (1 << CPUID).
-  __ movl(rax, Immediate(1));
-  __ and_(rcx, rax);  // Bit 0 is set if SAHF instruction supported.
-  __ not_(rax);
-  __ and_(rax, rdi);
-  __ or_(rax, rcx);
-  __ or_(rax, Immediate(1 << CPUID));
-
-  // Done.
-  __ bind(&done);
-  __ movq(rsp, rbp);
-  __ pop(rbx);
-  __ pop(rcx);
-  __ pop(rdi);
-  __ popfq();
-  __ pop(rbp);
-  __ ret(0);
-#undef __
-
-  typedef uint64_t (*F0)();
-  F0 probe = FUNCTION_CAST<F0>(reinterpret_cast<Address>(memory->address()));
-
-  uint64_t probed_features = probe();
   uint64_t platform_features = OS::CpuFeaturesImpliedByPlatform();
   supported_ = probed_features | platform_features;
   found_by_runtime_probing_only_
       = probed_features & ~kDefaultCpuFeatures & ~platform_features;
-
-  // CMOV must be available on an X64 CPU.
-  ASSERT(IsSupported(CPUID));
-  ASSERT(IsSupported(CMOV));
-
-  delete memory;
 }
 
 
@@ -987,7 +921,6 @@ void Assembler::cmpb_al(Immediate imm8) {
 
 
 void Assembler::cpuid() {
-  ASSERT(IsEnabled(CPUID));
   EnsureSpace ensure_space(this);
   emit(0x0F);
   emit(0xA2);