Add some helper functions for getting the intrinsic ID to use for a g…

…iven oper (#104498)

* Add some helper functions for getting the intrinsic ID to use for a given oper

* Make the Unix build happy

* Make the Arm64 build happy

* Respond to PR feedback

* Ensure we don't use EVEX unnecessarily

* Ensure zero diffs for x64

src/coreclr/jit/compiler.h

@@ -2597,6 +2597,7 @@ class Compiler
     friend class FlowGraphNaturalLoop;
 
 #ifdef FEATURE_HW_INTRINSICS
+    friend struct GenTreeHWIntrinsic;
     friend struct HWIntrinsicInfo;
     friend struct SimdAsHWIntrinsicInfo;
 #endif // FEATURE_HW_INTRINSICS
@@ -9569,6 +9570,21 @@ class Compiler
     // F+CD+DQ+BW+VL (such as VBMI) and should appear with a corresponding query around AVX512*_VL (i.e. AVX512_VBMI_VL)
 
 #ifdef DEBUG
+    //------------------------------------------------------------------------
+    // IsBaselineVector256IsaSupportedDebugOnly - Does isa support exist for Vector256.
+    //
+    // Returns:
+    //    `true` if AVX.
+    //
+    bool IsBaselineVector256IsaSupportedDebugOnly() const
+    {
+#ifdef TARGET_XARCH
+        return compIsaSupportedDebugOnly(InstructionSet_AVX);
+#else
+        return false;
+#endif
+    }
+
     //------------------------------------------------------------------------
     // IsBaselineVector512IsaSupportedDebugOnly - Does isa support exist for Vector512.
     //