8041957: -XX:UseAVX=0 cause assert(UseAVX) failed

Summary: temporary set UseAVX=1 and UseSSE=2 in generate_get_cpu_info()
Reviewed-by: twisti

src/cpu/x86/vm/assembler_x86.cpp

@@ -1766,7 +1766,7 @@ void Assembler::movdqu(Address dst, XMMRegister src) {
 
 // Move Unaligned 256bit Vector
 void Assembler::vmovdqu(XMMRegister dst, XMMRegister src) {
-  assert(UseAVX, "");
+  assert(UseAVX > 0, "");
   bool vector256 = true;
   int encode = vex_prefix_and_encode(dst, xnoreg, src, VEX_SIMD_F3, vector256);
   emit_int8(0x6F);
@@ -1774,7 +1774,7 @@ void Assembler::vmovdqu(XMMRegister dst, XMMRegister src) {
 }
 
 void Assembler::vmovdqu(XMMRegister dst, Address src) {
-  assert(UseAVX, "");
+  assert(UseAVX > 0, "");
   InstructionMark im(this);
   bool vector256 = true;
   vex_prefix(dst, xnoreg, src, VEX_SIMD_F3, vector256);
@@ -1783,7 +1783,7 @@ void Assembler::vmovdqu(XMMRegister dst, Address src) {
 }
 
 void Assembler::vmovdqu(Address dst, XMMRegister src) {
-  assert(UseAVX, "");
+  assert(UseAVX > 0, "");
   InstructionMark im(this);
   bool vector256 = true;
   // swap src<->dst for encoding

src/cpu/x86/vm/vm_version_x86.cpp

@@ -263,6 +263,10 @@ class VM_Version_StubGenerator: public StubCodeGenerator {
     // and check upper YMM bits after it.
     //
     VM_Version::set_avx_cpuFeatures(); // Enable temporary to pass asserts
+    intx saved_useavx = UseAVX;
+    intx saved_usesse = UseSSE;
+    UseAVX = 1;
+    UseSSE = 2;
 
     // load value into all 32 bytes of ymm7 register
     __ movl(rcx, VM_Version::ymm_test_value());
@@ -292,6 +296,8 @@ class VM_Version_StubGenerator: public StubCodeGenerator {
 #endif
 
     VM_Version::clean_cpuFeatures();
+    UseAVX = saved_useavx;
+    UseSSE = saved_usesse;
 
     //
     // cpuid(0x7) Structured Extended Features