AArch64: Extend intrinsics framework to account for merging predications without gp [PR121604]

In PR121604 the problem was noted that currently the SVE intrinsics
infrastructure assumes that for any predicated operation that the GP is at the
first argument position which has a svbool_t or for a unary merging operation
that it's in the second position.

However you have intrinsics like fmov_lane which have an svbool_t but it's not
a GP but instead it's the inactive lanes.

You also have instructions like BRKB which work only on predicates so it
incorrectly determines the first operand to be the GP, while that's also the
inactive lanes.

However during apply_predication we do have the information about where the GP
is.  This patch re-organizes the code to record this information into the
function_instance such that folders have access to this information.

For functions that are outliers like pmov_lane we can now override the
availability of the intrinsics having a GP.

gcc/ChangeLog:

	PR target/121604
	* config/aarch64/aarch64-sve-builtins-shapes.cc (apply_predication):
	Store gp_index.
	(struct pmov_to_vector_lane_def): Mark instruction as has no GP.
	* config/aarch64/aarch64-sve-builtins.h (function_instance::gp_value,
	function_instance::inactive_values, function_instance::gp_index,
	function_shape::has_gp_argument_p): New.
	* config/aarch64/aarch64-sve-builtins.cc (gimple_folder::fold_pfalse):
	Simplify code and use GP helpers.

gcc/testsuite/ChangeLog:

	PR target/121604
	* gcc.target/aarch64/sve/pr121604_brk.c: New test.
	* gcc.target/aarch64/sve2/pr121604_pmov.c: New test.

Co-authored-by: Jennifer Schmitz <jschmitz@nvidia.com>

gcc/config/aarch64/aarch64-sve-builtins-shapes.cc

@@ -21,7 +21,10 @@
 #include "system.h"
 #include "coretypes.h"
 #include "tm.h"
+#include "basic-block.h"
 #include "tree.h"
+#include "function.h"
+#include "gimple.h"
 #include "rtl.h"
 #include "tm_p.h"
 #include "memmodel.h"
@@ -68,23 +71,36 @@ za_group_is_pure_overload (const function_group_info &group)
    types in ARGUMENT_TYPES.  RETURN_TYPE is the type returned by the
    function.  */
 static void
-apply_predication (const function_instance &instance, tree return_type,
+apply_predication (function_instance &instance, tree return_type,
 		   vec<tree> &argument_types)
 {
+  /* Initially mark the function as not being predicated.  */
+  instance.gp_index = -1;
+
   /* There are currently no SME ZA instructions that have both merging and
      unpredicated forms, so for simplicity, the predicates are always included
      in the original format string.  */
   if (instance.pred != PRED_none && instance.pred != PRED_za_m)
     {
       argument_types.quick_insert (0, instance.gp_type ());
+      instance.gp_index = 0;
       /* For unary merge operations, the first argument is a vector with
 	 the same type as the result.  For unary_convert_narrowt it also
 	 provides the "bottom" half of active elements, and is present
 	 for all types of predication.  */
       auto nargs = argument_types.length () - 1;
       if (instance.shape->has_merge_argument_p (instance, nargs))
-	argument_types.quick_insert (0, return_type);
+	{
+	  argument_types.quick_insert (0, return_type);
+	  instance.gp_index = 1;
+	}
     }
+
+  /* In this case the predicate type we added above is a non-governing
+     predicate operand (and there is no GP), so update the gp_index value
+     accordingly.  */
+  if (!instance.shape->has_gp_argument_p (instance))
+    instance.gp_index = -1;
 }
 
 /* Parse and move past an element type in FORMAT and return it as a type
@@ -3332,6 +3348,14 @@ struct pmov_to_vector_lane_def : public overloaded_base<0>
        but it doesn't currently have the necessary information.  */
     return c.require_immediate_range (1, 1, bytes - 1);
   }
+
+  /* This function has a predicate argument, and is a merging instruction, but
+     the predicate is not a GP.  */
+  bool
+  has_gp_argument_p (const function_instance &) const override
+  {
+    return false;
+  }
 };
 SHAPE (pmov_to_vector_lane)
 

gcc/config/aarch64/aarch64-sve-builtins.cc

@@ -3632,24 +3632,22 @@ gimple_folder::redirect_pred_x ()
 gimple *
 gimple_folder::fold_pfalse ()
 {
-  if (pred == PRED_none)
+  tree gp = gp_value (call);
+  /* If there isn't a GP then we can't do any folding as the instruction isn't
+     predicated.  */
+  if (!gp)
     return nullptr;
-  tree arg0 = gimple_call_arg (call, 0);
+
   if (pred == PRED_m)
     {
-      /* Unary function shapes with _m predication are folded to the
-	 inactive vector (arg0), while other function shapes are folded
-	 to op1 (arg1).  */
-      tree arg1 = gimple_call_arg (call, 1);
-      if (is_pfalse (arg1))
-	return fold_call_to (arg0);
-      if (is_pfalse (arg0))
-	return fold_call_to (arg1);
+      tree val = inactive_values (call);
+      if (is_pfalse (gp))
+	return fold_call_to (val);
       return nullptr;
     }
-  if ((pred == PRED_x || pred == PRED_z) && is_pfalse (arg0))
+  if ((pred == PRED_x || pred == PRED_z) && is_pfalse (gp))
     return fold_call_to (build_zero_cst (TREE_TYPE (lhs)));
-  if (pred == PRED_implicit && is_pfalse (arg0))
+  if (pred == PRED_implicit && is_pfalse (gp))
     {
       unsigned int flags = call_properties ();
       /* Folding to lhs = {0, ...} is not appropriate for intrinsics with

gcc/config/aarch64/aarch64-sve-builtins.h

@@ -403,6 +403,8 @@ public:
   bool could_trap_p () const;
 
   vector_type_index gp_type_index () const;
+  tree gp_value (gcall *) const;
+  tree inactive_values (gcall *) const;
   tree gp_type () const;
 
   unsigned int vectors_per_tuple () const;
@@ -436,6 +438,7 @@ public:
   group_suffix_index group_suffix_id;
   predication_index pred;
   fpm_mode_index fpm_mode;
+  int gp_index;
 };
 
 class registered_function;
@@ -801,6 +804,8 @@ public:
   virtual bool has_merge_argument_p (const function_instance &,
 				     unsigned int) const;
 
+  virtual bool has_gp_argument_p (const function_instance &) const;
+
   virtual bool explicit_type_suffix_p (unsigned int) const = 0;
 
   /* True if the group suffix is present in overloaded names.
@@ -949,6 +954,33 @@ function_instance::gp_type () const
   return acle_vector_types[0][gp_type_index ()];
 }
 
+/* Return the tree value that should be used as the governing predicate of
+   this function.  If none then return NULL_TREE.  */
+inline tree
+function_instance::gp_value (gcall *call) const
+{
+  if (gp_index < 0)
+    return NULL_TREE;
+
+  return gimple_call_arg (call, gp_index);
+}
+
+/* Return the tree value that should be used for the inactive lanes should this
+   function be a predicated function with a gp.  Otherwise return NULL_TREE.  */
+inline tree
+function_instance::inactive_values (gcall *call) const
+{
+  if (gp_index < 0)
+    return NULL_TREE;
+
+  /* Function is unary with m predicate.  */
+  if (gp_index == 1)
+    return gimple_call_arg (call, 0);
+
+  /* Else the inactive values are the next element.  */
+  return gimple_call_arg (call, 1);
+}
+
 /* If the function operates on tuples of vectors, return the number
    of vectors in the tuples, otherwise return 1.  */
 inline unsigned int
@@ -1123,6 +1155,14 @@ function_shape::has_merge_argument_p (const function_instance &instance,
   return nargs == 1 && instance.pred == PRED_m;
 }
 
+/* Return true if INSTANCE has an predicate argument that can be used as the global
+   predicate.  */
+inline bool
+function_shape::has_gp_argument_p (const function_instance &instance) const
+{
+  return instance.pred != PRED_none;
+}
+
 /* Return the mode of the result of a call.  */
 inline machine_mode
 function_expander::result_mode () const

gcc/testsuite/gcc.target/aarch64/sve/pr121604_brk.c

@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { check-function-bodies "**" "" "" } } */
+
+#include <arm_sve.h>
+
+/*
+** foo:
+**	ptrue	p0\.b, all
+**	brkb	p0\.b, p0/z, p0\.b
+**	ret
+*/
+svbool_t foo () {
+  return svbrkb_b_m (svpfalse (), svptrue_b8 (), svptrue_b8 ());
+}
+
+/*
+** bar:
+**	ptrue	p0\.b, all
+**	brka	p0\.b, p0/z, p0\.b
+**	ret
+*/
+svbool_t bar () {
+  return svbrka_b_m (svpfalse (), svptrue_b8 (), svptrue_b8 ());
+}

gcc/testsuite/gcc.target/aarch64/sve2/pr121604_pmov.c

@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=armv8.2-a+sve2p1" } */
+/* { dg-final { check-function-bodies "**" "" "" } } */
+
+#include <arm_sve.h>
+
+/*
+** f:
+**	pfalse	p([0-7]+)\.b
+**	mov	z0\.b, #-1
+**	pmov	z0\[1\], p\1\.d
+**	ret
+*/
+svuint64_t f () {
+    return svpmov_lane_u64_m (svdup_u64 (~0UL), svpfalse (), 1);
+}