In implementing the ACLE read/write system register builtins it was
observed that leaving argument type checking to be done at expand-time
meant that poorly-formed function calls were being "fixed" by certain
optimization passes, meaning bad code wasn't being properly picked up
in checking.

Example:

  const char *regname = "amcgcr_el0";
  long long a = __builtin_aarch64_rsr64 (regname);

is reduced by the ccp1 pass to

  long long a = __builtin_aarch64_rsr64 ("amcgcr_el0");

As these functions require an argument of STRING_CST type, there needs
to be a check carried out by the front-end capable of picking this up.

The introduced `check_general_builtin_call' function will be called by
the TARGET_CHECK_BUILTIN_CALL hook whenever a call to a builtin
belonging to the AARCH64_BUILTIN_GENERAL category is encountered,
carrying out any appropriate checks associated with a particular
builtin function code.

gcc/ChangeLog:

        * config/aarch64/aarch64-builtins.cc (check_general_builtin_call):
        New.
        * config/aarch64/aarch64-c.cc (aarch64_check_builtin_call):
        Add check_general_builtin_call call.
        * config/aarch64/aarch64-protos.h (check_general_builtin_call):
        New.

gcc/testsuite/ChangeLog:

        * gcc.target/aarch64/acle/rwsr-3.c: New.
---
 gcc/config/aarch64/aarch64-builtins.cc        | 31 +++++++++++++++++++
 gcc/config/aarch64/aarch64-c.cc               |  4 +--
 gcc/config/aarch64/aarch64-protos.h           |  4 +++
 .../gcc.target/aarch64/acle/rwsr-3.c          | 18 +++++++++++
 4 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/aarch64/acle/rwsr-3.c

diff --git a/gcc/config/aarch64/aarch64-builtins.cc 
b/gcc/config/aarch64/aarch64-builtins.cc
index dd76cca611b..c5f20f68bca 100644
--- a/gcc/config/aarch64/aarch64-builtins.cc
+++ b/gcc/config/aarch64/aarch64-builtins.cc
@@ -2127,6 +2127,37 @@ aarch64_general_builtin_decl (unsigned code, bool)
   return aarch64_builtin_decls[code];
 }
 
+bool
+aarch64_check_general_builtin_call (location_t location, vec<location_t>,
+                           unsigned int code, tree fndecl,
+                           unsigned int nargs ATTRIBUTE_UNUSED, tree *args)
+{
+  switch (code)
+    {
+    case AARCH64_RSR:
+    case AARCH64_RSRP:
+    case AARCH64_RSR64:
+    case AARCH64_RSRF:
+    case AARCH64_RSRF64:
+    case AARCH64_WSR:
+    case AARCH64_WSRP:
+    case AARCH64_WSR64:
+    case AARCH64_WSRF:
+    case AARCH64_WSRF64:
+      if (TREE_CODE (args[0]) != NOP_EXPR
+         || TREE_CODE (TREE_TYPE (args[0])) != POINTER_TYPE
+         || (TREE_CODE (TREE_OPERAND (TREE_OPERAND (args[0], 0) , 0))
+             != STRING_CST))
+       {
+         error_at (location, "first argument to %qD must be a string literal",
+                   fndecl);
+         return false;
+       }
+    }
+  /* Default behavior.  */
+  return true;
+}
+
 typedef enum
 {
   SIMD_ARG_COPY_TO_REG,
diff --git a/gcc/config/aarch64/aarch64-c.cc b/gcc/config/aarch64/aarch64-c.cc
index ab8844f6049..be8b7236cf9 100644
--- a/gcc/config/aarch64/aarch64-c.cc
+++ b/gcc/config/aarch64/aarch64-c.cc
@@ -339,8 +339,8 @@ aarch64_check_builtin_call (location_t loc, vec<location_t> 
arg_loc,
   switch (code & AARCH64_BUILTIN_CLASS)
     {
     case AARCH64_BUILTIN_GENERAL:
-      return true;
-
+      return aarch64_check_general_builtin_call (loc, arg_loc, subcode,
+                                                orig_fndecl, nargs, args);
     case AARCH64_BUILTIN_SVE:
       return aarch64_sve::check_builtin_call (loc, arg_loc, subcode,
                                              orig_fndecl, nargs, args);
diff --git a/gcc/config/aarch64/aarch64-protos.h 
b/gcc/config/aarch64/aarch64-protos.h
index 5d6a1e75700..dbd486cfea4 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -990,6 +990,10 @@ tree aarch64_general_builtin_rsqrt (unsigned int);
 void handle_arm_acle_h (void);
 void handle_arm_neon_h (void);
 
+bool aarch64_check_general_builtin_call (location_t, vec<location_t>,
+                                        unsigned int, tree, unsigned int,
+                                        tree *);
+
 namespace aarch64_sve {
   void init_builtins ();
   void handle_arm_sve_h ();
diff --git a/gcc/testsuite/gcc.target/aarch64/acle/rwsr-3.c 
b/gcc/testsuite/gcc.target/aarch64/acle/rwsr-3.c
new file mode 100644
index 00000000000..17038fefbf6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/acle/rwsr-3.c
@@ -0,0 +1,18 @@
+/* Test the __arm_[r,w]sr ACLE intrinsics family.  */
+/* Ensure that illegal behavior is rejected by the compiler.  */
+
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -O3 -march=armv8.4-a" } */
+
+#include <arm_acle.h>
+
+void
+test_non_const_sysreg_name ()
+{
+  const char *regname = "trcseqstr";
+  long long a = __arm_rsr64 (regname); /* { dg-error "first argument to 
'__builtin_aarch64_rsr64' must be a string literal" } */
+  __arm_wsr64 (regname, a); /* { dg-error "first argument to 
'__builtin_aarch64_wsr64' must be a string literal" } */
+
+  long long b = __arm_rsr64(nullptr); /* { dg-error "first argument to 
'__builtin_aarch64_rsr64' must be a string literal" } */
+  __arm_wsr64(nullptr, b); /* { dg-error "first argument to 
'__builtin_aarch64_wsr64' must be a string literal" } */
+}
-- 
2.41.0

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