[gcc(refs/users/aoliva/heads/testme)] aarch64: enforce lane checking for intrinsics

[gcc(refs/users/aoliva/heads/testme)] aarch64: enforce lane checking for intrinsics

[Alexandre Oliva]

https://gcc.gnu.org/g:6b3ccde02fa88011273c3e875db18097662a298e

commit 6b3ccde02fa88011273c3e875db18097662a298e
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Mon Jan 22 13:04:09 2024 -0300

    aarch64: enforce lane checking for intrinsics
    
    Calling arm_neon.h functions that take lanes as arguments may fail to
    report malformed values if the intrinsic happens to be optimized away,
    e.g. because it is pure or const and the result is unused.
    
    Adding __AARCH64_LANE_CHECK calls to the always_inline functions would
    duplicate errors in case the intrinsics are not optimized away; using
    another preprocessor macro to call either the intrinsic or
    __builtin_aarch64_im_lane_boundsi moves the error messages to the
    arm_neon.h header, and may add warnings if we fall off the end of the
    functions; duplicating the code to avoid the undesirable effect of the
    macros doesn't seem appealing; separating the checking from alternate
    no-error-checking core/pure (invisible?) intrinsics in e.g. folding of
    non-const/pure (user-callable) intrinsics seems ugly and risky.
    
    So I propose dropping the pure/const attribute from the intrinsics and
    builtin declarations, so that gimple passes won't optimize them away.
    After expand (when errors are detected and reported), we get plain
    insns rather than calls, and those are dropped if the outputs are
    unused.  It's not ideal, it could be improved, but it's safe enough
    for this stage.
    
    
    for  gcc/ChangeLog
    
            * config/aarch64/aarch64-builtins.cc (aarch64_get_attributes):
            Add lane_check parm, to rule out pure and const.
            (aarch64_init_simd_intrinsics): Pass lane_check if any arg has
            lane index qualifiers.
            (aarch64_init_simd_builtin_functions): Likewise.

Diff:
---
 gcc/config/aarch64/aarch64-builtins.cc | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/gcc/config/aarch64/aarch64-builtins.cc b/gcc/config/aarch64/aarch64-builtins.cc
index 9b23b6b8c33..1268deea28e 100644
--- a/gcc/config/aarch64/aarch64-builtins.cc
+++ b/gcc/config/aarch64/aarch64-builtins.cc
@@ -1258,11 +1258,12 @@ aarch64_add_attribute (const char *name, tree attrs)
 /* Return the appropriate attributes for a function that has
    flags F and mode MODE.  */
 static tree
-aarch64_get_attributes (unsigned int f, machine_mode mode)
+aarch64_get_attributes (unsigned int f, machine_mode mode,
+			bool lane_check = false)
 {
   tree attrs = NULL_TREE;
 
-  if (!aarch64_modifies_global_state_p (f, mode))
+  if (!lane_check && !aarch64_modifies_global_state_p (f, mode))
     {
       if (aarch64_reads_global_state_p (f, mode))
 	attrs = aarch64_add_attribute ("pure", attrs);
@@ -1318,6 +1319,7 @@ aarch64_init_simd_intrinsics (void)
 
       tree return_type = void_type_node;
       tree args = void_list_node;
+      bool lane_check = false;
 
       for (int op_num = d->op_count - 1; op_num >= 0; op_num--)
 	{
@@ -1330,10 +1332,17 @@ aarch64_init_simd_intrinsics (void)
 	    return_type = eltype;
 	  else
 	    args = tree_cons (NULL_TREE, eltype, args);
+
+	  if (qualifiers & (qualifier_lane_index
+			    | qualifier_struct_load_store_lane_index
+			    | qualifier_lane_pair_index
+			    | qualifier_lane_quadtup_index))
+	    lane_check = true;
 	}
 
       tree ftype = build_function_type (return_type, args);
-      tree attrs = aarch64_get_attributes (d->flags, d->op_modes[0]);
+      tree attrs = aarch64_get_attributes (d->flags, d->op_modes[0],
+					   lane_check);
       unsigned int code
 	      = (d->fcode << AARCH64_BUILTIN_SHIFT | AARCH64_BUILTIN_GENERAL);
       tree fndecl = simulate_builtin_function_decl (input_location, d->name,
@@ -1400,6 +1409,7 @@ aarch64_init_simd_builtin_functions (bool called_from_pragma)
 	  || (!called_from_pragma && struct_mode_args > 0))
 	continue;
 
+      bool lane_check = false;
       /* Build a function type directly from the insn_data for this
 	 builtin.  The build_function_type () function takes care of
 	 removing duplicates for us.  */
@@ -1435,6 +1445,12 @@ aarch64_init_simd_builtin_functions (bool called_from_pragma)
 	    return_type = eltype;
 	  else
 	    args = tree_cons (NULL_TREE, eltype, args);
+
+	  if (qualifiers & (qualifier_lane_index
+			    | qualifier_struct_load_store_lane_index
+			    | qualifier_lane_pair_index
+			    | qualifier_lane_quadtup_index))
+	    lane_check = true;
 	}
 
       ftype = build_function_type (return_type, args);
@@ -1448,7 +1464,7 @@ aarch64_init_simd_builtin_functions (bool called_from_pragma)
 	snprintf (namebuf, sizeof (namebuf), "__builtin_aarch64_%s",
 		  d->name);
 
-      tree attrs = aarch64_get_attributes (d->flags, d->mode);
+      tree attrs = aarch64_get_attributes (d->flags, d->mode, lane_check);
 
       if (called_from_pragma)
 	{