[C++ PATCH] Make same_type_p return false for gnu_vector_type_p differences (PR 92789)

Richard Sandiford richard.sandiford@arm.com
Thu Dec 19 16:59:00 GMT 2019


Jason Merrill <jason@redhat.com> writes:
> On 12/12/19 10:16 AM, Richard Sandiford wrote:
>> As Jason pointed out in the review of the C++ gnu_vector_type_p patch:
>> 
>>      https://gcc.gnu.org/ml/gcc-patches/2019-12/msg00173.html
>> 
>> the real fix for the XFAILs in acle/general-c++/gnu_vectors_*.C is to
>> make same_type_p return false for two types if one is gnu_vector_type_p
>> and the other isn't.  This patch does that and fixes the fallout in the
>> way Jason suggested above.
>> 
>> I'd said at the time that some of the tests require:
>> 
>>        /* If the constructor already has the array type, it's been through
>> 	 digest_init, so we shouldn't try to do anything more.  */
>>        bool digested = same_type_p (atype, TREE_TYPE (init));
>> 
>> (build_vec_init) to be true for gnu vectors built from non-gnu vectors.
>> I can no longer reproduce that, maybe because my original same_type_p
>> change was bogus or because something in the later sizeless type
>> support made it moot (or something else :-)).
>> 
>> This means that sve-sizeless-2.C (the length-specific test) now reports
>> some errors for comparisons and pointer differences that sve-sizeless-1.C
>> (the length-agnostic test) already had.  I think requiring a cast is OK
>> for those cases, since there's no reason to mix GNU and non-GNU versions
>> of the same vector in the same object.  Even -flax-vector-conversions
>> would require a cast for different vector types here, for both C and C++.
>> 
>> same_type_p had:
>> 
>>    else if (strict == COMPARE_STRUCTURAL)
>>      return structural_comptypes (t1, t2, COMPARE_STRICT);
>>    else
>>      return structural_comptypes (t1, t2, strict);
>> 
>> Since structural_comptypes ignored the COMPARE_STRUCTURAL bit of "strict"
>> before the patch, the "else if" was harmless but AFAICT unnecessary.
>
> The comment in cp-tree.h has
>
>> #define COMPARE_STRUCTURAL    8 /* The comparison is intended to be                                            
>>                                    structural. The actual comparison                                           
>>                                    will be identical to                                                        
>>                                    COMPARE_STRICT.  */
>
> So introducing differences between COMPARE_STRUCTURAL and COMPARE_STRICT 
> other than that the first always calls structural_comptypes and the 
> second sometimes compares TYPE_CANONICAL instead is to be avoided.

OK.

> Do you want to use vector_types_convertible_p in similar_type_p?

The problem then is that we'll apply -flax-vector-conversion rules too,
which seems to be going too far beyond what [conv.qual] says.

But that's probably a sign that I was wanting the wrong behaviour here.
The main point is to ensure that similar GNU and non-GNU vectors remain
interconveritble without -flax-vector-conversions, and without any
warnings.  There's no specific requirement to extend that to pointers,
it just seemed like the natural thing to do at the time.

So on reflection, I guess we should just accept the consequences of
making the types !same_type_p.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.  OK to install?
If so, I'll follow up with a corresponding patch for C.

Thanks,
Richard


2019-12-19  Richard Sandiford  <richard.sandiford@arm.com>

gcc/cp/
	PR c++/92789
	* typeck.c (structural_comptypes): Make sure that two vector types
	agree on gnu_vector_type_p.

gcc/testsuite/
	PR c++/92789
	* g++.dg/ext/sve-sizeless-2.C (statements): Expect pointer
	difference and comparisons between GNU and non-GNU types
	to be rejected.  Expect __is_same to be false for such pairs.
	* g++.target/aarch64/sve/acle/general-c++/gnu_vectors_1.C: Remove
	XFAILs.  Expect conversions between SVE vector pointers and
	GNU vector pointers to be rejected.  Test references.
	* g++.target/aarch64/sve/acle/general-c++/gnu_vectors_2.C: Likewise.

Index: gcc/cp/typeck.c
===================================================================
--- gcc/cp/typeck.c	2019-12-19 16:28:40.344411888 +0000
+++ gcc/cp/typeck.c	2019-12-19 16:43:03.490702766 +0000
@@ -1425,7 +1425,8 @@ structural_comptypes (tree t1, tree t2,
       break;
 
     case VECTOR_TYPE:
-      if (maybe_ne (TYPE_VECTOR_SUBPARTS (t1), TYPE_VECTOR_SUBPARTS (t2))
+      if (gnu_vector_type_p (t1) != gnu_vector_type_p (t2)
+	  || maybe_ne (TYPE_VECTOR_SUBPARTS (t1), TYPE_VECTOR_SUBPARTS (t2))
 	  || !same_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
 	return false;
       break;
Index: gcc/testsuite/g++.dg/ext/sve-sizeless-2.C
===================================================================
--- gcc/testsuite/g++.dg/ext/sve-sizeless-2.C	2019-12-13 10:21:18.000000000 +0000
+++ gcc/testsuite/g++.dg/ext/sve-sizeless-2.C	2019-12-19 16:43:03.490702766 +0000
@@ -183,8 +183,8 @@ statements (int n)
 
   // Pointer assignment.
 
-  gnu_sc_ptr = sve_sc_ptr;
-  sve_sc_ptr = gnu_sc_ptr;
+  gnu_sc_ptr = sve_sc_ptr; // { dg-error {invalid conversion from 'svint8_t\*' to 'int8x32_t\*'} }
+  sve_sc_ptr = gnu_sc_ptr; // { dg-error {invalid conversion from 'int8x32_t\*'[^\n]* to 'svint8_t\*'} }
 
   // Pointer arithmetic.
 
@@ -197,8 +197,8 @@ statements (int n)
   sve_sc_ptr -= 0; // { dg-error {arithmetic on pointer to SVE type 'svint8_t'} }
   sve_sc_ptr -= 1; // { dg-error {arithmetic on pointer to SVE type 'svint8_t'} }
   sve_sc_ptr - sve_sc_ptr; // { dg-error {arithmetic on pointer to SVE type 'svint8_t'} }
-  gnu_sc_ptr - sve_sc_ptr; // { dg-error {arithmetic on pointer to SVE type 'svint8_t'} }
-  sve_sc_ptr - gnu_sc_ptr; // { dg-error {arithmetic on pointer to SVE type 'svint8_t'} }
+  gnu_sc_ptr - sve_sc_ptr; // { dg-error {invalid operands of types 'int8x32_t\*'[^\n]* and 'svint8_t\*' to binary 'operator-'} }
+  sve_sc_ptr - gnu_sc_ptr; // { dg-error {invalid operands of types 'svint8_t\*' and 'int8x32_t\*'[^\n]* to binary 'operator-'} }
   sve_sc1 = sve_sc_ptr[0]; // { dg-error {arithmetic on pointer to SVE type 'svint8_t'} }
   sve_sc1 = sve_sc_ptr[1]; // { dg-error {arithmetic on pointer to SVE type 'svint8_t'} }
 
@@ -210,18 +210,18 @@ statements (int n)
   sve_sc_ptr <= &sve_sc1;
   sve_sc_ptr > &sve_sc1;
   sve_sc_ptr >= &sve_sc1;
-  gnu_sc_ptr == sve_sc_ptr;
-  gnu_sc_ptr != sve_sc_ptr;
-  gnu_sc_ptr < sve_sc_ptr;
-  gnu_sc_ptr <= sve_sc_ptr;
-  gnu_sc_ptr > sve_sc_ptr;
-  gnu_sc_ptr >= sve_sc_ptr;
-  sve_sc_ptr == gnu_sc_ptr;
-  sve_sc_ptr != gnu_sc_ptr;
-  sve_sc_ptr < gnu_sc_ptr;
-  sve_sc_ptr <= gnu_sc_ptr;
-  sve_sc_ptr > gnu_sc_ptr;
-  sve_sc_ptr >= gnu_sc_ptr;
+  gnu_sc_ptr == sve_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  gnu_sc_ptr != sve_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  gnu_sc_ptr < sve_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  gnu_sc_ptr <= sve_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  gnu_sc_ptr > sve_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  gnu_sc_ptr >= sve_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  sve_sc_ptr == gnu_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  sve_sc_ptr != gnu_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  sve_sc_ptr < gnu_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  sve_sc_ptr <= gnu_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  sve_sc_ptr > gnu_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
+  sve_sc_ptr >= gnu_sc_ptr; // { dg-error {comparison between distinct pointer types [^\n]*lacks a cast} }
 
   // New and delete.
 
@@ -243,8 +243,8 @@ statements (int n)
   0 ? 0 : sve_sc1; // { dg-error {different types 'int' and 'svint8_t'} }
   0 ? sve_sc1 : sve_sc1;
   0 ? sve_sc_ptr : sve_sc_ptr;
-  0 ? sve_sc_ptr : gnu_sc_ptr;
-  0 ? gnu_sc_ptr : sve_sc_ptr;
+  0 ? sve_sc_ptr : gnu_sc_ptr; // { dg-error {conditional expression between distinct pointer types [^\n]*lacks a cast} }
+  0 ? gnu_sc_ptr : sve_sc_ptr; // { dg-error {conditional expression between distinct pointer types [^\n]*lacks a cast} }
 
   // Function arguments.
 
@@ -321,11 +321,11 @@ statements (int n)
   { typedef int f[__is_pod (svint8_t) ? 1 : -1]; }
   { typedef int f[!__is_polymorphic (svint8_t) ? 1 : -1]; }
   { typedef int f[__is_same_as (svint8_t, svint8_t) ? 1 : -1]; }
-  { typedef int f[__is_same_as (svint8_t, int8x32_t) ? 1 : -1]; }
-  { typedef int f[__is_same_as (int8x32_t, svint8_t) ? 1 : -1]; }
+  { typedef int f[!__is_same_as (svint8_t, int8x32_t) ? 1 : -1]; }
+  { typedef int f[!__is_same_as (int8x32_t, svint8_t) ? 1 : -1]; }
   { typedef int f[__is_same_as (svint8_t *, svint8_t *) ? 1 : -1]; }
-  { typedef int f[__is_same_as (svint8_t *, int8x32_t *) ? 1 : -1]; }
-  { typedef int f[__is_same_as (int8x32_t *, svint8_t *) ? 1 : -1]; }
+  { typedef int f[!__is_same_as (svint8_t *, int8x32_t *) ? 1 : -1]; }
+  { typedef int f[!__is_same_as (int8x32_t *, svint8_t *) ? 1 : -1]; }
   { typedef int f[!__is_same_as (svint8_t, int) ? 1 : -1]; }
   { typedef int f[!__is_same_as (svint8_t, svint16_t) ? 1 : -1]; }
   { typedef int f[__is_trivial (svint8_t) ? 1 : -1]; }
Index: gcc/testsuite/g++.target/aarch64/sve/acle/general-c++/gnu_vectors_1.C
===================================================================
--- gcc/testsuite/g++.target/aarch64/sve/acle/general-c++/gnu_vectors_1.C	2019-12-13 10:21:18.000000000 +0000
+++ gcc/testsuite/g++.target/aarch64/sve/acle/general-c++/gnu_vectors_1.C	2019-12-19 16:43:03.490702766 +0000
@@ -36,14 +36,14 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
 
   gnu_uint8_t init_gnu_u1 = 0; // { dg-error {cannot convert 'int' to 'gnu_uint8_t'[^\n]* in initialization} }
   gnu_uint8_t init_gnu_u2 = {};
-  gnu_uint8_t init_gnu_u3 = { sve_u1 };
+  gnu_uint8_t init_gnu_u3 = { sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u4 = { gnu_u1 };
   gnu_uint8_t init_gnu_u5 = { sve_s1 }; // { dg-error {cannot convert 'svint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u6 = { gnu_s1 }; // { dg-error {cannot convert 'gnu_int8_t'[^\n]* to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u7 = { 0 };
   gnu_uint8_t init_gnu_u8 = { sve_u1, sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u9 = { gnu_u1, gnu_u1 }; // { dg-error {cannot convert 'gnu_uint8_t'[^\n]* to 'unsigned char' in initialization} }
-  gnu_uint8_t init_gnu_u10 { sve_u1 };
+  gnu_uint8_t init_gnu_u10 { sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u11 { gnu_u1 };
   gnu_uint8_t init_gnu_u12 { sve_s1 }; // { dg-error {cannot convert 'svint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u13 { gnu_s1 }; // { dg-error {cannot convert 'gnu_int8_t'[^\n]* to 'unsigned char' in initialization} }
@@ -69,7 +69,7 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
 
   (gnu_uint8_t) {};
   (gnu_uint8_t) { 0 };
-  (gnu_uint8_t) { sve_u1 };
+  (gnu_uint8_t) { sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   (gnu_uint8_t) { gnu_u1 };
   (gnu_uint8_t) { sve_s1 }; // { dg-error {cannot convert 'svint8_t' to 'unsigned char' in initialization} }
   (gnu_uint8_t) { gnu_s1 }; // { dg-error {cannot convert 'gnu_int8_t'[^\n]* to 'unsigned char' in initialization} }
@@ -434,8 +434,8 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
   // Conditional expressions.
 
   uc ? sve_u1 : sve_u1;
-  uc ? gnu_u1 : sve_u1; // { dg-error {operands to '\?:' have different types 'gnu_uint8_t'[^\n]* and 'svuint8_t'} "" { xfail *-*-* } }
-  uc ? sve_u1 : gnu_u1; // { dg-error {operands to '\?:' have different types 'svuint8_t' and 'gnu_uint8_t'} "" { xfail *-*-* } }
+  uc ? gnu_u1 : sve_u1; // { dg-error {operands to '\?:' have different types 'gnu_uint8_t'[^\n]* and 'svuint8_t'} }
+  uc ? sve_u1 : gnu_u1; // { dg-error {operands to '\?:' have different types 'svuint8_t' and 'gnu_uint8_t'} }
   uc ? gnu_u1 : gnu_u1;
 
   sve_u1 ? sve_u1 : sve_u1; // { dg-error {could not convert 'sve_u1' from 'svuint8_t' to 'bool'} }
@@ -474,15 +474,29 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
   static_assert(__is_literal_type(svuint8_t));
   static_assert(__is_literal_type(gnu_uint8_t));
 
+  // Pointers.
+
   svuint8_t *sve_ptr1 = &sve_u1;
-  svuint8_t *sve_ptr2 = &gnu_u1;
+  svuint8_t *sve_ptr2 = &gnu_u1; // { dg-error {invalid conversion} }
   svuint8_t *sve_ptr3 = &sve_s1; // { dg-error {cannot convert 'svint8_t\*' to 'svuint8_t\*' in initialization} }
   svuint8_t *sve_ptr4 = &gnu_s1; // { dg-error {cannot convert 'gnu_int8_t\*'[^\n]* to 'svuint8_t\*' in initialization} }
 
-  gnu_uint8_t *gnu_ptr1 = &sve_u1;
+  gnu_uint8_t *gnu_ptr1 = &sve_u1; // { dg-error {invalid conversion} }
   gnu_uint8_t *gnu_ptr2 = &gnu_u1;
   gnu_uint8_t *gnu_ptr3 = &sve_s1; // { dg-error {cannot convert 'svint8_t\*' to 'gnu_uint8_t\*'} }
   gnu_uint8_t *gnu_ptr4 = &gnu_s1; // { dg-error {cannot convert 'gnu_int8_t\*'[^\n]* to 'gnu_uint8_t\*'} }
+
+  // References.
+
+  svuint8_t &sve_ref1 = sve_u1;
+  svuint8_t &sve_ref2 = gnu_u1; // { dg-error {cannot bind non-const lvalue reference} }
+  svuint8_t &sve_ref3 = sve_s1; // { dg-error {invalid initialization of reference of type 'svuint8_t\&' from expression of type 'svint8_t'} }
+  svuint8_t &sve_ref4 = gnu_s1; // { dg-error {invalid initialization of reference of type 'svuint8_t\&' from expression of type 'gnu_int8_t'} }
+
+  gnu_uint8_t &gnu_ref1 = sve_u1; // { dg-error {cannot bind non-const lvalue reference} }
+  gnu_uint8_t &gnu_ref2 = gnu_u1;
+  gnu_uint8_t &gnu_ref3 = sve_s1; // { dg-error {invalid initialization of reference of type 'gnu_uint8_t\&} }
+  gnu_uint8_t &gnu_ref4 = gnu_s1; // { dg-error {invalid initialization of reference of type 'gnu_uint8_t\&} }
 }
 
 constexpr svuint8_t const1 (svuint8_t x) { return x; }
Index: gcc/testsuite/g++.target/aarch64/sve/acle/general-c++/gnu_vectors_2.C
===================================================================
--- gcc/testsuite/g++.target/aarch64/sve/acle/general-c++/gnu_vectors_2.C	2019-12-13 10:21:18.000000000 +0000
+++ gcc/testsuite/g++.target/aarch64/sve/acle/general-c++/gnu_vectors_2.C	2019-12-19 16:43:03.490702766 +0000
@@ -36,14 +36,14 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
 
   gnu_uint8_t init_gnu_u1 = 0; // { dg-error {cannot convert 'int' to 'gnu_uint8_t'[^\n]* in initialization} }
   gnu_uint8_t init_gnu_u2 = {};
-  gnu_uint8_t init_gnu_u3 = { sve_u1 };
+  gnu_uint8_t init_gnu_u3 = { sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u4 = { gnu_u1 };
   gnu_uint8_t init_gnu_u5 = { sve_s1 }; // { dg-error {cannot convert 'svint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u6 = { gnu_s1 }; // { dg-error {cannot convert 'gnu_int8_t'[^\n]* to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u7 = { 0 };
   gnu_uint8_t init_gnu_u8 = { sve_u1, sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u9 = { gnu_u1, gnu_u1 }; // { dg-error {cannot convert 'gnu_uint8_t'[^\n]* to 'unsigned char' in initialization} }
-  gnu_uint8_t init_gnu_u10 { sve_u1 };
+  gnu_uint8_t init_gnu_u10 { sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u11 { gnu_u1 };
   gnu_uint8_t init_gnu_u12 { sve_s1 }; // { dg-error {cannot convert 'svint8_t' to 'unsigned char' in initialization} }
   gnu_uint8_t init_gnu_u13 { gnu_s1 }; // { dg-error {cannot convert 'gnu_int8_t'[^\n]* to 'unsigned char' in initialization} }
@@ -69,7 +69,7 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
 
   (gnu_uint8_t) {};
   (gnu_uint8_t) { 0 };
-  (gnu_uint8_t) { sve_u1 };
+  (gnu_uint8_t) { sve_u1 }; // { dg-error {cannot convert 'svuint8_t' to 'unsigned char' in initialization} }
   (gnu_uint8_t) { gnu_u1 };
   (gnu_uint8_t) { sve_s1 }; // { dg-error {cannot convert 'svint8_t' to 'unsigned char' in initialization} }
   (gnu_uint8_t) { gnu_s1 }; // { dg-error {cannot convert 'gnu_int8_t'[^\n]* to 'unsigned char' in initialization} }
@@ -434,8 +434,8 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
   // Conditional expressions.
 
   uc ? sve_u1 : sve_u1;
-  uc ? gnu_u1 : sve_u1; // { dg-error {operands to '\?:' have different types 'gnu_uint8_t'[^\n]* and 'svuint8_t'} "" { xfail *-*-* } }
-  uc ? sve_u1 : gnu_u1; // { dg-error {operands to '\?:' have different types 'svuint8_t' and 'gnu_uint8_t'} "" { xfail *-*-* } }
+  uc ? gnu_u1 : sve_u1; // { dg-error {operands to '\?:' have different types 'gnu_uint8_t'[^\n]* and 'svuint8_t'} }
+  uc ? sve_u1 : gnu_u1; // { dg-error {operands to '\?:' have different types 'svuint8_t' and 'gnu_uint8_t'} }
   uc ? gnu_u1 : gnu_u1;
 
   sve_u1 ? sve_u1 : sve_u1; // { dg-error {could not convert 'sve_u1' from 'svuint8_t' to 'bool'} }
@@ -474,15 +474,29 @@ f (svuint8_t sve_u1, svint8_t sve_s1,
   static_assert(__is_literal_type(svuint8_t));
   static_assert(__is_literal_type(gnu_uint8_t));
 
+  // Pointers.
+
   svuint8_t *sve_ptr1 = &sve_u1;
-  svuint8_t *sve_ptr2 = &gnu_u1;
+  svuint8_t *sve_ptr2 = &gnu_u1; // { dg-error {invalid conversion} }
   svuint8_t *sve_ptr3 = &sve_s1; // { dg-error {invalid conversion from 'svint8_t\*' to 'svuint8_t\*'} }
   svuint8_t *sve_ptr4 = &gnu_s1; // { dg-error {invalid conversion from 'gnu_int8_t\*'[^\n]* to 'svuint8_t\*'} }
 
-  gnu_uint8_t *gnu_ptr1 = &sve_u1;
+  gnu_uint8_t *gnu_ptr1 = &sve_u1; // { dg-error {invalid conversion} }
   gnu_uint8_t *gnu_ptr2 = &gnu_u1;
   gnu_uint8_t *gnu_ptr3 = &sve_s1; // { dg-error {invalid conversion from 'svint8_t\*' to 'gnu_uint8_t\*'} }
   gnu_uint8_t *gnu_ptr4 = &gnu_s1; // { dg-error {invalid conversion from 'gnu_int8_t\*'[^\n]* to 'gnu_uint8_t\*'} }
+
+  // References.
+
+  svuint8_t &sve_ref1 = sve_u1;
+  svuint8_t &sve_ref2 = gnu_u1; // { dg-error {cannot bind non-const lvalue reference} }
+  svuint8_t &sve_ref3 = sve_s1; // { dg-error {cannot bind non-const lvalue reference} }
+  svuint8_t &sve_ref4 = gnu_s1; // { dg-error {cannot bind non-const lvalue reference} }
+
+  gnu_uint8_t &gnu_ref1 = sve_u1; // { dg-error {cannot bind non-const lvalue reference} }
+  gnu_uint8_t &gnu_ref2 = gnu_u1;
+  gnu_uint8_t &gnu_ref3 = sve_s1; // { dg-error {cannot bind non-const lvalue reference} }
+  gnu_uint8_t &gnu_ref4 = gnu_s1; // { dg-error {cannot bind non-const lvalue reference} }
 }
 
 constexpr svuint8_t const1 (svuint8_t x) { return x; }



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