[PATCH 2/4][AArch64]Improve error message for non-constant immediates

[Alan Lawrence <alan dot lawrence at arm dot com>]

The error message when passing a non-constant in place of an immediate to an 
arm_neon.h *intrinsic* (as programmers should, rather than the __builtin), is poor:

In file included from gcc/testsuite/gcc.target/aarch64/arg-type-diagnostics-1.c:4:0:
/work/alalaw01/oban/buildfsf-aarch64-none-elf/install/lib/gcc/aarch64-none-elf/5.0.0/include/arm_neon.h: 
In function 'foo':
/work/alalaw01/oban/buildfsf-aarch64-none-elf/install/lib/gcc/aarch64-none-elf/5.0.0/include/arm_neon.h:21752:10: 
error: incompatible type for argument 3, expected 'const int'
return (int32x2_t) __builtin_aarch64_srsra_nv2si (__a, __b, __c);

...the line number references arm_neon.h, and the meaning of 'const int' is 
distinct from what that means in C! Similarly to the previous patch, this patch 
improves this to:

In file included from gcc/testsuite/gcc.target/aarch64/arg-type-diagnostics-1.c:4:0:
In function 'vrsra_n_s32',
  inlined from 'foo' at 
gcc/testsuite/gcc.target/aarch64/arg-type-diagnostics-1.c:13:10:
/work/alalaw01/oban/buildfsf-aarch64-none-elf/install/lib/gcc/aarch64-none-elf/5.0.0/include/arm_neon.h:21752:10: 
error: argument 3 must be a constant immediate
return (int32x2_t) __builtin_aarch64_srsra_nv2si (__a, __b, __c);

(This shows arg-type-diagnostics-1.c:13:10, as the actual source line containing 
the error).

The code for SIMD_ARG_CONSTANT also covers non-constant lane indices, so error 
messages there are improved too.

gcc/ChangeLog:

	* gcc/config/aarch64-builtins.c (aarch64_simd_expand_args): Update error
	message for SIMD_ARG_CONSTANT.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/arg-type-diagnostics-1.c: Call intrinsic, update
	expected error message.

diff --git a/gcc/config/aarch64/aarch64-builtins.c b/gcc/config/aarch64/aarch64-builtins.c
index f8e14ab40637b66302f5cc194ae9507e37a248f9..09fd49648922a197d4d0a5f4d230af77ee0e31ba 100644
--- a/gcc/config/aarch64/aarch64-builtins.c
+++ b/gcc/config/aarch64/aarch64-builtins.c
@@ -925,8 +925,8 @@ aarch64_simd_expand_args (rtx target, int icode, int have_retval,
 	      if (!(*insn_data[icode].operand[argc + have_retval].predicate)
 		  (op[argc], mode[argc]))
 	      {
-		error_at (EXPR_LOCATION (exp), "incompatible type for argument %d, "
-		       "expected %<const int%>", argc + 1);
+		error ("%Kargument %d must be a constant immediate",
+		       exp, argc + 1);
 		return const0_rtx;
 	      }
 	      break;
diff --git a/gcc/testsuite/gcc.target/aarch64/arg-type-diagnostics-1.c b/gcc/testsuite/gcc.target/aarch64/arg-type-diagnostics-1.c
index 55dd9f66f23cf6e6eff67bd68d875d24c0460d13..a7b7cd3bd8d40faaabbe48a1d382e9860d4497ff 100644
--- a/gcc/testsuite/gcc.target/aarch64/arg-type-diagnostics-1.c
+++ b/gcc/testsuite/gcc.target/aarch64/arg-type-diagnostics-1.c
@@ -3,13 +3,16 @@
 
 #include "arm_neon.h"
 
-void foo ()
+void foo (int a)
 {
-  int a;
   int32x2_t arg1;
   int32x2_t arg2;
   int32x2_t result;
   arg1 = vcreate_s32 (UINT64_C (0x0000ffffffffffff));
   arg2 = vcreate_s32 (UINT64_C (0x16497fffffffffff));
-  result = __builtin_aarch64_srsra_nv2si (arg1, arg2, a); /* { dg-error "incompatible type for argument" } */
+  /* The correct line number is in the preamble to the error message,
+     not in the final line (which is all that dg-error inspects). Hence,
+     we have to tell dg-error to ignore the line number.  */
+  result = vrsra_n_s32 (arg1, arg2, a);
+  /* { dg-error "must be a constant immediate" "" { target *-*-* } 0 } */
 }