[committed 2/5 v2] aarch64: Fix FMV array iteration bounds

[Andrew Carlotti]

There was an assumption in some places that the aarch64_fmv_feature_data
array contained FEAT_MAX elements.  While this assumption held up till
now, it is safer and more flexible to use the array size directly.

Also fix the lower bound in compare_feature_masks to use ">=0" instead
of ">0", and add a test using the features at index 0 and 1. However,
the test already passed, because the earlier popcount check makes it
impossible to reach the loop if the masks differ in exactly one
location.

gcc/ChangeLog:

        * config/aarch64/aarch64.cc (compare_feature_masks):
        Use ARRAY_SIZE and >=0 for iteration bounds.
        (aarch64_mangle_decl_assembler_name): Use ARRAY_SIZE.

gcc/testsuite/ChangeLog:

        * g++.target/aarch64/mv-1.C: New test.


diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 
1ea84c8bd7386e399f6ffa3a5e36408cf8831fc6..4f708213551523b4af966ac8521754df5eb6bf3c
 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -19700,7 +19700,7 @@ aarch64_parse_fmv_features (const char *str, 
aarch64_feature_flags *isa_flags,
       if (len == 0)
        return AARCH_PARSE_MISSING_ARG;
 
-      static const int num_features = ARRAY_SIZE (aarch64_fmv_feature_data);
+      int num_features = ARRAY_SIZE (aarch64_fmv_feature_data);
       int i;
       for (i = 0; i < num_features; i++)
        {
@@ -19899,7 +19899,8 @@ compare_feature_masks (aarch64_fmv_feature_mask mask1,
   auto diff_mask = mask1 ^ mask2;
   if (diff_mask == 0ULL)
     return 0;
-  for (int i = FEAT_MAX - 1; i > 0; i--)
+  int num_features = ARRAY_SIZE (aarch64_fmv_feature_data);
+  for (int i = num_features - 1; i >= 0; i--)
     {
       auto bit_mask = aarch64_fmv_feature_data[i].feature_mask;
       if (diff_mask & bit_mask)
@@ -19982,7 +19983,8 @@ aarch64_mangle_decl_assembler_name (tree decl, tree id)
 
       name += "._";
 
-      for (int i = 0; i < FEAT_MAX; i++)
+      int num_features = ARRAY_SIZE (aarch64_fmv_feature_data);
+      for (int i = 0; i < num_features; i++)
        {
          if (feature_mask & aarch64_fmv_feature_data[i].feature_mask)
            {
diff --git a/gcc/testsuite/g++.target/aarch64/mv-1.C 
b/gcc/testsuite/g++.target/aarch64/mv-1.C
new file mode 100644
index 
0000000000000000000000000000000000000000..b4b0e5e3fea0ed481de1918d30cd8248bb4f7ab5
--- /dev/null
+++ b/gcc/testsuite/g++.target/aarch64/mv-1.C
@@ -0,0 +1,38 @@
+/* { dg-do compile } */
+/* { dg-require-ifunc "" } */
+/* { dg-options "-O0" } */
+
+__attribute__((target_version("default")))
+int foo ()
+{
+  return 1;
+}
+
+__attribute__((target_version("rng")))
+int foo ()
+{
+  return 1;
+}
+
+__attribute__((target_version("flagm")))
+int foo ()
+{
+  return 1;
+}
+
+__attribute__((target_version("rng+flagm")))
+int foo ()
+{
+  return 1;
+}
+
+int bar()
+{
+  return foo ();
+}
+
+/* Check usage of the first two FMV features, in case of off-by-one errors.  */
+/* { dg-final { scan-assembler-times "\n_Z3foov\.default:\n" 1 } } */
+/* { dg-final { scan-assembler-times "\n_Z3foov\._Mrng:\n" 1 } } */
+/* { dg-final { scan-assembler-times "\n_Z3foov\._MrngMflagm:\n" 1 } } */
+/* { dg-final { scan-assembler-times "\n_Z3foov\._Mflagm:\n" 1 } } */