[clang][X86] Allow VALIGND/Q element-shift intrinsics in constexpr evaluation (#168206)

Fixes #167681

1 files changed, 22 insertions, 0 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index ce5301f17b3e..bc885f4c8902 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -13627,6 +13627,28 @@ bool VectorExprEvaluator::VisitCallExpr(const CallExpr *E) {
       return false;
     return Success(R, E);
   }
+  case X86::BI__builtin_ia32_alignd128:
+  case X86::BI__builtin_ia32_alignd256:
+  case X86::BI__builtin_ia32_alignd512:
+  case X86::BI__builtin_ia32_alignq128:
+  case X86::BI__builtin_ia32_alignq256:
+  case X86::BI__builtin_ia32_alignq512: {
+    APValue R;
+    unsigned NumElems = E->getType()->castAs<VectorType>()->getNumElements();
+    if (!evalShuffleGeneric(Info, E, R,
+                            [NumElems](unsigned DstIdx, unsigned Shift) {
+                              unsigned Imm = Shift & 0xFF;
+                              unsigned EffectiveShift = Imm & (NumElems - 1);
+                              unsigned SourcePos = DstIdx + EffectiveShift;
+                              unsigned VecIdx = SourcePos < NumElems ? 1 : 0;
+                              unsigned ElemIdx = SourcePos & (NumElems - 1);
+
+                              return std::pair<unsigned, int>{
+                                  VecIdx, static_cast<int>(ElemIdx)};
+                            }))
+      return false;
+    return Success(R, E);
+  }
   case X86::BI__builtin_ia32_permvarsi256:
   case X86::BI__builtin_ia32_permvarsf256:
   case X86::BI__builtin_ia32_permvardf512: