[clang][AArch64/SVE] Avoid crash when checking conversion between SVL type and SVE tuple (fixes llvm#26)

Author: iamlouk

clang/lib/AST/ASTContext.cpp

@@ -10086,6 +10086,13 @@ bool ASTContext::areCompatibleSveTypes(QualType FirstType,
                                        QualType SecondType) {
   auto IsValidCast = [this](QualType FirstType, QualType SecondType) {
     if (const auto *BT = FirstType->getAs<BuiltinType>()) {
+      // SVE tuple types such as svuint32x4_t are SVE builtin types as well,
+      // but they are not compatible for casts to/from normal vectors.
+      // isSveVLSBuiltinType() happes to only over the vectors, and not the
+      // tuples.
+      if (!BT->isSveVLSBuiltinType())
+        return false;
+
       if (const auto *VT = SecondType->getAs<VectorType>()) {
         // Predicates have the same representation as uint8 so we also have to
         // check the kind to make these types incompatible.

clang/test/CodeGen/attr-arm-sve-vector-bits-cast.c

@@ -111,3 +111,14 @@ fixed_int32_t to_fixed_int32_t__from_gnu_int32_t(gnu_int32_t type) {
 gnu_int32_t from_fixed_int32_t__to_gnu_int32_t(fixed_int32_t type) {
   return type;
 }
+
+// Regression test for SiPearl-internal error:
+// https://gitlab01.int.sipearl.com/software/compilers/llvm-project-sipearl-fork/-/issues/26
+// CHECK-LABEL: @reinterpret_from_fixed_to_scalable(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[TMP0:%.*]] = bitcast <vscale x 4 x i32> [[A_COERCE:%.*]] to <vscale x 4 x float>
+// CHECK-NEXT:    ret <vscale x 4 x float> [[TMP0]]
+//
+svfloat32_t reinterpret_from_fixed_to_scalable(fixed_int32_t a) {
+  return svreinterpret_f32(a);
+}