[clang] Replace interp__builtin_blend with interp__builtin_ia32_shuffle_gener… (PR #170217)

[Timm Baeder via cfe-commits]

================
@@ -4624,7 +4624,15 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const CallExpr *Call,
   case clang::X86::BI__builtin_ia32_pblendw256:
   case clang::X86::BI__builtin_ia32_pblendd128:
   case clang::X86::BI__builtin_ia32_pblendd256:
-    return interp__builtin_blend(S, OpPC, Call);
+    return interp__builtin_ia32_shuffle_generic(
+      S, OpPC, Call, [](unsigned DstIdx, unsigned ShuffleMask) {
+        // bit index for mask
+        unsigned maskBit = (ShuffleMask >> (DstIdx % 8)) & 0x1;
----------------
tbaederr wrote:

```suggestion
        // Bit index for mask.
        unsigned MaskBit = (ShuffleMask >> (DstIdx % 8)) & 0x1;
```

https://github.com/llvm/llvm-project/pull/170217