Adding EVEX encoding pathways for emitOutputRRR().

Adding flag to turn on EVEX encoding.

Author: DeepakRajendrakumaran

src/coreclr/jit/compiler.cpp

@@ -2284,6 +2284,11 @@ void Compiler::compSetProcessor()
 #ifdef TARGET_XARCH
     if (!compIsForInlining())
     {
+        if (canUseEvexEncoding())
+        {
+            codeGen->GetEmitter()->SetUseEVEXEncoding(true);
+            // TODO-XArch-AVX512: Revisit other flags to be set once avx512 instructions are added.
+        }
         if (canUseVexEncoding())
         {
             codeGen->GetEmitter()->SetUseVEXEncoding(true);

src/coreclr/jit/compiler.h

@@ -8923,6 +8923,15 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 #endif
     }
 
+    bool canUseEvexEncoding() const
+    {
+#ifdef TARGET_XARCH
+        return compOpportunisticallyDependsOn(InstructionSet_AVX512F);
+#else
+        return false;
+#endif
+    }
+
     /*
     XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
     XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

src/coreclr/jit/emit.h

@@ -445,6 +445,7 @@ class emitter
 
 #ifdef TARGET_XARCH
         SetUseVEXEncoding(false);
+        SetUseEVEXEncoding(false);
 #endif // TARGET_XARCH
 
         emitDataSecCur = nullptr;