[clang][Interp] Handle BooleanToSignedIntegral casts

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -343,6 +343,7 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
   }
 
   case CK_IntegralToBoolean:
+  case CK_BooleanToSignedIntegral:
   case CK_IntegralCast: {
     if (DiscardResult)
       return this->discard(SubExpr);
@@ -362,7 +363,12 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
 
     if (FromT == ToT)
       return true;
-    return this->emitCast(*FromT, *ToT, CE);
+    if (!this->emitCast(*FromT, *ToT, CE))
+      return false;
+
+    if (CE->getCastKind() == CK_BooleanToSignedIntegral)
+      return this->emitNeg(*ToT, CE);
+    return true;
   }
 
   case CK_PointerToBoolean:

clang/test/AST/Interp/vectors.cpp

@@ -61,3 +61,12 @@ namespace {
   typedef float __attribute__((vector_size(16))) VI42;
   constexpr VI42 A2 = A; // expected-error {{must be initialized by a constant expression}}
 }
+
+namespace BoolToSignedIntegralCast{
+  typedef __attribute__((__ext_vector_type__(4))) unsigned int int4;
+  constexpr int4 intsT = (int4)true;
+  static_assert(intsT[0] == -1, "");// ref-error {{not an integral constant expression}}
+  static_assert(intsT[1] == -1, "");// ref-error {{not an integral constant expression}}
+  static_assert(intsT[2] == -1, "");// ref-error {{not an integral constant expression}}
+  static_assert(intsT[3] == -1, "");// ref-error {{not an integral constant expression}}
+}