Hey,

Added the warn_pcs_change_le_gcc14 variable and changed the uses of warn_pcs_change to use this new variable. Also fixed an issue with the loop through TREE_FIELDS to avoid an ICE during bootstrap.

OK for trunk?

Bootstrapped and regression tested on aarch64-unknown-linux-gnu.

Kind regards,
Andre

On 28/03/2024 12:54, Richard Sandiford wrote:
"Andre Vieira (lists)" <andre.simoesdiasvie...@arm.com> writes:
This patch makes sure we do not give ABI change diagnostics for the ABI
breaks of GCC 9, 13 and 14 for any type involving _BitInt(N), since that
type did not exist before this GCC version.

ChangeLog:

        * config/aarch64/aarch64.cc (bitint_or_aggr_of_bitint_p): New function.
        (aarch64_layout_arg): Don't emit diagnostics for types involving
        _BitInt(N).

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 
1ea84c8bd7386e399f6ffa3a5e36408cf8831fc6..b68cf3e7cb9a6fa89b4e5826a39ffa11f64ca20a
 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -6744,6 +6744,33 @@ aarch64_function_arg_alignment (machine_mode mode, 
const_tree type,
    return alignment;
  }
+/* Return true if TYPE describes a _BitInt(N) or an angreggate that uses the
+   _BitInt(N) type.  These include ARRAY_TYPE's with an element that is a
+   _BitInt(N) or an aggregate that uses it, and a RECORD_TYPE or a UNION_TYPE
+   with a field member that is a _BitInt(N) or an aggregate that uses it.
+   Return false otherwise.  */
+
+static bool
+bitint_or_aggr_of_bitint_p (tree type)
+{
+  if (!type)
+    return false;
+
+  if (TREE_CODE (type) == BITINT_TYPE)
+    return true;
+
+  /* If ARRAY_TYPE, check it's element type.  */
+  if (TREE_CODE (type) == ARRAY_TYPE)
+    return bitint_or_aggr_of_bitint_p (TREE_TYPE (type));
+
+  /* If RECORD_TYPE or UNION_TYPE, check the fields' types.  */
+  if (RECORD_OR_UNION_TYPE_P (type))
+    for (tree field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
+      if (bitint_or_aggr_of_bitint_p (TREE_TYPE (field)))
+       return true;
+  return false;
+}
+
  /* Layout a function argument according to the AAPCS64 rules.  The rule
     numbers refer to the rule numbers in the AAPCS64.  ORIG_MODE is the
     mode that was originally given to us by the target hook, whereas the
@@ -6767,12 +6794,6 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const 
function_arg_info &arg)
    if (pcum->aapcs_arg_processed)
      return;
- bool warn_pcs_change
-    = (warn_psabi
-       && !pcum->silent_p
-       && (currently_expanding_function_start
-          || currently_expanding_gimple_stmt));
-
    /* HFAs and HVAs can have an alignment greater than 16 bytes.  For example:
typedef struct foo {
@@ -6907,6 +6928,18 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const 
function_arg_info &arg)
              && (!alignment || abi_break_gcc_9 < alignment)
              && (!abi_break_gcc_13 || alignment < abi_break_gcc_13));
+
+  bool warn_pcs_change
+    = (warn_psabi
+       && !pcum->silent_p
+       && (currently_expanding_function_start
+          || currently_expanding_gimple_stmt)
+      /* warn_pcs_change is currently used to gate diagnostics in case of
+        abi_break_gcc_{9,13,14}.  These however, do not apply to _BitInt(N)
+        types as they were only introduced in GCC 14.  */
+       && (!type || !bitint_or_aggr_of_bitint_p (type)));

How about making this a new variable such as:

   /* _BitInt(N) was only added in GCC 14.  */
   bool warn_pcs_change_le_gcc14
     = (warn_psabi && !bitint_or_aggr_of_bitint_p (type);

(and keeping warn_pcs_change where it is).  In principle, warn_pcs_change
is meaningful for any future ABI breaks, and we might forget that it
excludes bitints.  The name is just a suggestion.

OK with that change, thanks.

Richard

+
+
    /* allocate_ncrn may be false-positive, but allocate_nvrn is quite reliable.
       The following code thus handles passing by SIMD/FP registers first.  */
@@ -21266,19 +21299,25 @@ aarch64_gimplify_va_arg_expr (tree valist, tree type, gimple_seq *pre_p,
        rsize = ROUND_UP (size, UNITS_PER_WORD);
        nregs = rsize / UNITS_PER_WORD;
- if (align <= 8 && abi_break_gcc_13 && warn_psabi)
+      if (align <= 8
+         && abi_break_gcc_13
+         && warn_psabi
+         && !bitint_or_aggr_of_bitint_p (type))
        inform (input_location, "parameter passing for argument of type "
                "%qT changed in GCC 13.1", type);
if (warn_psabi
          && abi_break_gcc_14
-         && (abi_break_gcc_14 > 8 * BITS_PER_UNIT) != (align > 8))
+         && (abi_break_gcc_14 > 8 * BITS_PER_UNIT) != (align > 8)
+         && !bitint_or_aggr_of_bitint_p (type))
        inform (input_location, "parameter passing for argument of type "
                "%qT changed in GCC 14.1", type);
if (align > 8)
        {
-         if (abi_break_gcc_9 && warn_psabi)
+         if (abi_break_gcc_9
+             && warn_psabi
+             && !bitint_or_aggr_of_bitint_p (type))
            inform (input_location, "parameter passing for argument of type "
                    "%qT changed in GCC 9.1", type);
          dw_align = true;
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 
1ea84c8bd7386e399f6ffa3a5e36408cf8831fc6..81400cc666472ffeff40df14e98ae00ebc774d31
 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -6744,6 +6744,37 @@ aarch64_function_arg_alignment (machine_mode mode, 
const_tree type,
   return alignment;
 }
 
+/* Return true if TYPE describes a _BitInt(N) or an angreggate that uses the
+   _BitInt(N) type.  These include ARRAY_TYPE's with an element that is a
+   _BitInt(N) or an aggregate that uses it, and a RECORD_TYPE or a UNION_TYPE
+   with a field member that is a _BitInt(N) or an aggregate that uses it.
+   Return false otherwise.  */
+
+static bool
+bitint_or_aggr_of_bitint_p (tree type)
+{
+  if (!type)
+    return false;
+
+  if (TREE_CODE (type) == BITINT_TYPE)
+    return true;
+
+  /* If ARRAY_TYPE, check it's element type.  */
+  if (TREE_CODE (type) == ARRAY_TYPE)
+    return bitint_or_aggr_of_bitint_p (TREE_TYPE (type));
+
+  /* If RECORD_TYPE or UNION_TYPE, check the fields' types.  */
+  if (RECORD_OR_UNION_TYPE_P (type))
+    for (tree field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
+      {
+       if (TREE_CODE (field) != FIELD_DECL)
+         continue;
+       if (bitint_or_aggr_of_bitint_p (TREE_TYPE (field)))
+         return true;
+      }
+  return false;
+}
+
 /* Layout a function argument according to the AAPCS64 rules.  The rule
    numbers refer to the rule numbers in the AAPCS64.  ORIG_MODE is the
    mode that was originally given to us by the target hook, whereas the
@@ -6907,6 +6938,11 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const 
function_arg_info &arg)
              && (!alignment || abi_break_gcc_9 < alignment)
              && (!abi_break_gcc_13 || alignment < abi_break_gcc_13));
 
+  /* _BitInt(N) was only added in GCC 14.  */
+  bool warn_pcs_change_le_gcc14
+    = warn_pcs_change && !bitint_or_aggr_of_bitint_p (type);
+
+
   /* allocate_ncrn may be false-positive, but allocate_nvrn is quite reliable.
      The following code thus handles passing by SIMD/FP registers first.  */
 
@@ -6978,14 +7014,14 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const 
function_arg_info &arg)
        {
          /* Emit a warning if the alignment changed when taking the
             'packed' attribute into account.  */
-         if (warn_pcs_change
+         if (warn_pcs_change_le_gcc14
              && abi_break_gcc_13
              && ((abi_break_gcc_13 == 16 * BITS_PER_UNIT)
                  != (alignment == 16 * BITS_PER_UNIT)))
            inform (input_location, "parameter passing for argument of type "
                    "%qT changed in GCC 13.1", type);
 
-         if (warn_pcs_change
+         if (warn_pcs_change_le_gcc14
              && abi_break_gcc_14
              && ((abi_break_gcc_14 == 16 * BITS_PER_UNIT)
                  != (alignment == 16 * BITS_PER_UNIT)))
@@ -6998,7 +7034,8 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const 
function_arg_info &arg)
             passed by reference rather than value.  */
          if (alignment == 16 * BITS_PER_UNIT)
            {
-             if (warn_pcs_change && abi_break_gcc_9)
+             if (warn_pcs_change_le_gcc14
+                 && abi_break_gcc_9)
                inform (input_location, "parameter passing for argument of type 
"
                        "%qT changed in GCC 9.1", type);
              ++ncrn;
@@ -7056,14 +7093,14 @@ aarch64_layout_arg (cumulative_args_t pcum_v, const 
function_arg_info &arg)
 on_stack:
   pcum->aapcs_stack_words = size / UNITS_PER_WORD;
 
-  if (warn_pcs_change
+  if (warn_pcs_change_le_gcc14
       && abi_break_gcc_13
       && ((abi_break_gcc_13 >= 16 * BITS_PER_UNIT)
          != (alignment >= 16 * BITS_PER_UNIT)))
     inform (input_location, "parameter passing for argument of type "
            "%qT changed in GCC 13.1", type);
 
-  if (warn_pcs_change
+  if (warn_pcs_change_le_gcc14
       && abi_break_gcc_14
       && ((abi_break_gcc_14 >= 16 * BITS_PER_UNIT)
          != (alignment >= 16 * BITS_PER_UNIT)))
@@ -7075,7 +7112,8 @@ on_stack:
       int new_size = ROUND_UP (pcum->aapcs_stack_size, 16 / UNITS_PER_WORD);
       if (pcum->aapcs_stack_size != new_size)
        {
-         if (warn_pcs_change && abi_break_gcc_9)
+         if (warn_pcs_change_le_gcc14
+             && abi_break_gcc_9)
            inform (input_location, "parameter passing for argument of type "
                    "%qT changed in GCC 9.1", type);
          pcum->aapcs_stack_size = new_size;
@@ -21266,19 +21304,25 @@ aarch64_gimplify_va_arg_expr (tree valist, tree type, 
gimple_seq *pre_p,
       rsize = ROUND_UP (size, UNITS_PER_WORD);
       nregs = rsize / UNITS_PER_WORD;
 
-      if (align <= 8 && abi_break_gcc_13 && warn_psabi)
+      if (align <= 8
+         && abi_break_gcc_13
+         && warn_psabi
+         && !bitint_or_aggr_of_bitint_p (type))
        inform (input_location, "parameter passing for argument of type "
                "%qT changed in GCC 13.1", type);
 
       if (warn_psabi
          && abi_break_gcc_14
-         && (abi_break_gcc_14 > 8 * BITS_PER_UNIT) != (align > 8))
+         && (abi_break_gcc_14 > 8 * BITS_PER_UNIT) != (align > 8)
+         && !bitint_or_aggr_of_bitint_p (type))
        inform (input_location, "parameter passing for argument of type "
                "%qT changed in GCC 14.1", type);
 
       if (align > 8)
        {
-         if (abi_break_gcc_9 && warn_psabi)
+         if (abi_break_gcc_9
+             && warn_psabi
+             && !bitint_or_aggr_of_bitint_p (type))
            inform (input_location, "parameter passing for argument of type "
                    "%qT changed in GCC 9.1", type);
          dw_align = true;

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