[gcc r14-9919] aarch64: Fix FMV array iteration bounds

[gcc r14-9919] aarch64: Fix FMV array iteration bounds

[Andrew Carlotti]

https://gcc.gnu.org/g:3ef14f56343ad3445f874638700f6b82f032a1ae

commit r14-9919-g3ef14f56343ad3445f874638700f6b82f032a1ae
Author: Andrew Carlotti <andrew.carlotti@arm.com>
Date:   Wed Apr 3 23:35:08 2024 +0100

    aarch64: Fix FMV array iteration bounds
    
    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:
---
 gcc/config/aarch64/aarch64.cc           |  8 ++++---
 gcc/testsuite/g++.target/aarch64/mv-1.C | 38 +++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index c763a8a6298..91481f9fada 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -19738,7 +19738,7 @@ 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++)
 	{
@@ -19937,7 +19937,8 @@ 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)
@@ -20020,7 +20021,8 @@ 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 00000000000..b4b0e5e3fea
--- /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 } } */