[clang][bytecode] Emit better diagnostic for invalid shufflevector index (#111643)

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -3586,8 +3586,9 @@ bool Compiler<Emitter>::VisitShuffleVectorExpr(const ShuffleVectorExpr *E) {
   }
   for (unsigned I = 0; I != NumOutputElems; ++I) {
     APSInt ShuffleIndex = E->getShuffleMaskIdx(Ctx.getASTContext(), I);
+    assert(ShuffleIndex >= -1);
     if (ShuffleIndex == -1)
-      return this->emitInvalid(E); // FIXME: Better diagnostic.
+      return this->emitInvalidShuffleVectorIndex(I, E);
 
     assert(ShuffleIndex < (NumInputElems * 2));
     if (!this->emitGetLocal(PT_Ptr,

clang/lib/AST/ByteCode/Interp.cpp

@@ -21,6 +21,7 @@
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
+#include "clang/Basic/DiagnosticSema.h"
 #include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/StringExtras.h"
 #include <limits>
@@ -1406,6 +1407,14 @@ bool handleFixedPointOverflow(InterpState &S, CodePtr OpPC,
   return S.noteUndefinedBehavior();
 }
 
+bool InvalidShuffleVectorIndex(InterpState &S, CodePtr OpPC, uint32_t Index) {
+  const SourceInfo &Loc = S.Current->getSource(OpPC);
+  S.FFDiag(Loc,
+           diag::err_shufflevector_minus_one_is_undefined_behavior_constexpr)
+      << Index;
+  return false;
+}
+
 // https://github.com/llvm/llvm-project/issues/102513
 #if defined(_WIN32) && !defined(__clang__) && !defined(NDEBUG)
 #pragma optimize("", off)

clang/lib/AST/ByteCode/Interp.h

@@ -161,6 +161,7 @@ bool CallBI(InterpState &S, CodePtr OpPC, const Function *Func,
 bool CallPtr(InterpState &S, CodePtr OpPC, uint32_t ArgSize,
              const CallExpr *CE);
 bool CheckLiteralType(InterpState &S, CodePtr OpPC, const Type *T);
+bool InvalidShuffleVectorIndex(InterpState &S, CodePtr OpPC, uint32_t Index);
 
 template <typename T>
 static bool handleOverflow(InterpState &S, CodePtr OpPC, const T &SrcValue) {

clang/lib/AST/ByteCode/Opcodes.td

@@ -773,6 +773,9 @@ def InvalidDeclRef : Opcode {
 }
 
 def SizelessVectorElementSize : Opcode;
+def InvalidShuffleVectorIndex : Opcode {
+  let Args = [ArgUint32];
+}
 
 def Assume : Opcode;
 

clang/test/AST/ByteCode/builtin-functions.cpp

@@ -956,7 +956,7 @@ namespace shufflevector {
   static_assert(vectorShuffle6[7] == 7, "");
 
   constexpr vector4char  vectorShuffleFail1 = __builtin_shufflevector( // both-error {{must be initialized by a constant expression}}\
-                                                                       // ref-error {{index for __builtin_shufflevector not within the bounds of the input vectors; index of -1 found at position 0 is not permitted in a constexpr context}}
+                                                                       // both-error {{index for __builtin_shufflevector not within the bounds of the input vectors; index of -1 found at position 0 is not permitted in a constexpr context}}
           vector4charConst1,
           vector4charConst2, -1, -1, -1, -1);
 }