[clang] [Clang] Generalize interp__builtin_ia32_shuffle_generic to handle single op permute shuffles. (PR #167236)

[Simon Pilgrim via cfe-commits]

================
@@ -4555,22 +4471,59 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, 
const CallExpr *Call,
   case X86::BI__builtin_ia32_pshufb128:
   case X86::BI__builtin_ia32_pshufb256:
   case X86::BI__builtin_ia32_pshufb512:
-    return interp__builtin_ia32_pshufb(S, OpPC, Call);
+    return interp__builtin_ia32_shuffle_generic(
+        S, OpPC, Call, [](unsigned DstIdx, unsigned ShuffleMask) {
+          uint8_t Ctlb = static_cast<uint8_t>(ShuffleMask);
+          if (Ctlb & 0x80)
+            return std::make_pair(0, -1);
+
+          unsigned LaneBase = (DstIdx / 16) * 16;
+          unsigned SrcOffset = Ctlb & 0x0F;
+          unsigned SrcIdx = LaneBase + SrcOffset;
+          return std::make_pair(0, static_cast<int>(SrcIdx));
+        });
 
   case X86::BI__builtin_ia32_pshuflw:
   case X86::BI__builtin_ia32_pshuflw256:
   case X86::BI__builtin_ia32_pshuflw512:
-    return interp__builtin_ia32_pshuf(S, OpPC, Call, false);
+    return interp__builtin_ia32_shuffle_generic(
+        S, OpPC, Call, [](unsigned DstIdx, unsigned ShuffleMask) {
+          unsigned LaneBase = (DstIdx / 8) * 8;
+          unsigned LaneIdx = DstIdx % 8;
+          if (LaneIdx < 4) {
+            unsigned Sel = (ShuffleMask >> (2 * LaneIdx)) & 0x3;
+            return std::make_pair(0, static_cast<int>(LaneBase + Sel));
+          }
+
+          return std::make_pair(0, static_cast<int>(DstIdx));
+        });
 
   case X86::BI__builtin_ia32_pshufhw:
   case X86::BI__builtin_ia32_pshufhw256:
   case X86::BI__builtin_ia32_pshufhw512:
-    return interp__builtin_ia32_pshuf(S, OpPC, Call, true);
+    return interp__builtin_ia32_shuffle_generic(
+        S, OpPC, Call, [](unsigned DstIdx, unsigned ShuffleMask) {
+          unsigned LaneBase = (DstIdx / 8) * 8;
+          unsigned LaneIdx = DstIdx % 8;
+          if (LaneIdx >= 4) {
+            unsigned Sel = (ShuffleMask >> (2 * (LaneIdx - 4))) & 0x3;
+            return std::make_pair(0, static_cast<int>(LaneBase + 4 + Sel));
+          }
+
+          return std::make_pair(0, static_cast<int>(DstIdx));
+          }
+        });
----------------
RKSimon wrote:

extra brace? clang-format? 

https://github.com/llvm/llvm-project/pull/167236
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