[PATCH][GCC][ARM] Implement a stricter self check.

[Tamar Christina]

Hi All,

This patch makes the self-test for the ARM options validations a bit
stricter.

When you specify a new architecture extension, neither the options flag in
arm-cpus.in nor the ISA definition in arm.h should contain any other
architecture bits, as this will confuse the parser. The options will be added
but it won't behave as expected.

This patch adds a stronger claim, which says you're not allowed to repeat any
feature bits already enabled by the parent architecture. This forces you to have
the smallest definition as possible for your option and also prevents the 
problem
stated above.

Regtested on arm-none-linux-eabi and no regressions.

Ok for trunk?

gcc/
2017-07-20  Tamar Christina  <tamar.christ...@arm.com>

        * config/arm/arm.c (arm_test_cpu_arch_dat):
        Check for overlap.
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 139ab701a956c27f40d23529f065c535ed8e19fd..c3feb4983c73c7141b7c0799644c45df429d41d8 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -31222,12 +31222,15 @@ namespace selftest {
    inconsistencies in the option extensions at present (extensions
    that duplicate others but aren't marked as aliases).  Furthermore,
    for correct canonicalization later options must never be a subset
-   of an earlier option.  */
+   of an earlier option.  Any extension should also only specify other
+   feature bits and never an architecture bit.  The architecture is inferred
+   from the declaration of the extension.  */
 static void
 arm_test_cpu_arch_data (void)
 {
   const arch_option *arch;
   const cpu_option *cpu;
+  auto_sbitmap target_isa (isa_num_bits);
   auto_sbitmap isa1 (isa_num_bits);
   auto_sbitmap isa2 (isa_num_bits);
 
@@ -31238,6 +31241,8 @@ arm_test_cpu_arch_data (void)
       if (arch->common.extensions == NULL)
 	continue;
 
+      arm_initialize_isa (target_isa, arch->common.isa_bits);
+
       for (ext1 = arch->common.extensions; ext1->name != NULL; ++ext1)
 	{
 	  if (ext1->alias)
@@ -31250,7 +31255,13 @@ arm_test_cpu_arch_data (void)
 		continue;
 
 	      arm_initialize_isa (isa2, ext2->isa_bits);
+	      /* If the option is a subset of the parent option, it doesn't
+		 add anything and so isn't useful.  */
 	      ASSERT_TRUE (!bitmap_subset_p (isa2, isa1));
+
+	      /* If the extension specifies any architectural bits then
+		 disallow it.  Extensions should only specify feature bits.  */
+	      ASSERT_TRUE (!bitmap_intersect_p (isa2, target_isa));
 	    }
 	}
     }
@@ -31262,6 +31273,8 @@ arm_test_cpu_arch_data (void)
       if (cpu->common.extensions == NULL)
 	continue;
 
+      arm_initialize_isa (target_isa, arch->common.isa_bits);
+
       for (ext1 = cpu->common.extensions; ext1->name != NULL; ++ext1)
 	{
 	  if (ext1->alias)
@@ -31274,7 +31287,13 @@ arm_test_cpu_arch_data (void)
 		continue;
 
 	      arm_initialize_isa (isa2, ext2->isa_bits);
+	      /* If the option is a subset of the parent option, it doesn't
+		 add anything and so isn't useful.  */
 	      ASSERT_TRUE (!bitmap_subset_p (isa2, isa1));
+
+	      /* If the extension specifies any architectural bits then
+		 disallow it.  Extensions should only specify feature bits.  */
+	      ASSERT_TRUE (!bitmap_intersect_p (isa2, target_isa));
 	    }
 	}
     }