diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -9529,9 +9529,10 @@
 
 bool ASTContext::areCompatibleSveTypes(QualType FirstType,
                                        QualType SecondType) {
-  assert(((FirstType->isSizelessBuiltinType() && SecondType->isVectorType()) ||
-          (FirstType->isVectorType() && SecondType->isSizelessBuiltinType())) &&
-         "Expected SVE builtin type and vector type!");
+  assert(
+      ((FirstType->isSVESizelessBuiltinType() && SecondType->isVectorType()) ||
+       (FirstType->isVectorType() && SecondType->isSVESizelessBuiltinType())) &&
+      "Expected SVE builtin type and vector type!");
 
   auto IsValidCast = [this](QualType FirstType, QualType SecondType) {
     if (const auto *BT = FirstType->getAs<BuiltinType>()) {
@@ -9558,9 +9559,10 @@
 
 bool ASTContext::areLaxCompatibleSveTypes(QualType FirstType,
                                           QualType SecondType) {
-  assert(((FirstType->isSizelessBuiltinType() && SecondType->isVectorType()) ||
-          (FirstType->isVectorType() && SecondType->isSizelessBuiltinType())) &&
-         "Expected SVE builtin type and vector type!");
+  assert(
+      ((FirstType->isSVESizelessBuiltinType() && SecondType->isVectorType()) ||
+       (FirstType->isVectorType() && SecondType->isSVESizelessBuiltinType())) &&
+      "Expected SVE builtin type and vector type!");
 
   auto IsLaxCompatible = [this](QualType FirstType, QualType SecondType) {
     const auto *BT = FirstType->getAs<BuiltinType>();
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -9871,8 +9871,8 @@
     }
 
     // Allow assignments between fixed-length and sizeless SVE vectors.
-    if ((LHSType->isSizelessBuiltinType() && RHSType->isVectorType()) ||
-        (LHSType->isVectorType() && RHSType->isSizelessBuiltinType()))
+    if ((LHSType->isSVESizelessBuiltinType() && RHSType->isVectorType()) ||
+        (LHSType->isVectorType() && RHSType->isSVESizelessBuiltinType()))
       if (Context.areCompatibleSveTypes(LHSType, RHSType) ||
           Context.areLaxCompatibleSveTypes(LHSType, RHSType)) {
         Kind = CK_BitCast;
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1750,7 +1750,8 @@
     }
   }
 
-  if (ToType->isSizelessBuiltinType() || FromType->isSizelessBuiltinType())
+  if (ToType->isSVESizelessBuiltinType() ||
+      FromType->isSVESizelessBuiltinType())
     if (S.Context.areCompatibleSveTypes(FromType, ToType) ||
         S.Context.areLaxCompatibleSveTypes(FromType, ToType)) {
       ICK = ICK_SVE_Vector_Conversion;
diff --git a/clang/test/Sema/attr-riscv-rvv-vector-bits.c b/clang/test/Sema/attr-riscv-rvv-vector-bits.c
--- a/clang/test/Sema/attr-riscv-rvv-vector-bits.c
+++ b/clang/test/Sema/attr-riscv-rvv-vector-bits.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +zve64x -ffreestanding -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +f -target-feature +d -target-feature +zve64d -ffreestanding -fsyntax-only -verify %s
 
 // TODO: Support for a arm_sve_vector_bits like attribute will come in the future.
 
@@ -60,3 +60,21 @@
 
   gs8 = gs8 & ss8; // expected-error {{invalid operands to binary expression ('gnu_int8_t' (vector of 8 'int8_t' values) and 'vint8m1_t' (aka '__rvv_int8m1_t'))}}
 }
+
+// --------------------------------------------------------------------------//
+// Implicit casts
+
+gnu_int8_t to_gnu_int8_t_from_vint8m1_t_(vint8m1_t x) { return x; } // expected-error {{returning 'vint8m1_t' (aka '__rvv_int8m1_t') from a function with incompatible result type 'gnu_int8_t' (vector of 8 'int8_t' values)}}
+vint8m1_t from_gnu_int8_t_to_vint8m1_t(gnu_int8_t x) { return x; } // expected-error {{returning 'gnu_int8_t' (vector of 8 'int8_t' values) from a function with incompatible result type 'vint8m1_t' (aka '__rvv_int8m1_t')}}
+
+// --------------------------------------------------------------------------//
+// Test passing GNU vector scalable function
+
+vint32m1_t __attribute__((overloadable)) vfunc(vint32m1_t op1, vint32m1_t op2);
+vfloat64m1_t __attribute__((overloadable)) vfunc(vfloat64m1_t op1, vfloat64m1_t op2);
+
+gnu_int32_t call_int32_ff(gnu_int32_t op1, gnu_int32_t op2) {
+  return vfunc(op1, op2); // expected-error {{no matching function for call to 'vfunc'}}
+                          // expected-note@-5 {{candidate function not viable: no known conversion from 'gnu_int32_t' (vector of 2 'int32_t' values) to 'vint32m1_t' (aka '__rvv_int32m1_t') for 1st argument}}
+                          // expected-note@-5 {{candidate function not viable: no known conversion from 'gnu_int32_t' (vector of 2 'int32_t' values) to 'vfloat64m1_t' (aka '__rvv_float64m1_t') for 1st argument}}
+}