tree-optimization/111779 - Handle some BIT_FIELD_REFs in SRA

The following handles byte-aligned, power-of-two and byte-multiple
sized BIT_FIELD_REF reads in SRA.  In particular this should cover
BIT_FIELD_REFs created by optimize_bit_field_compare.

For gcc.dg/tree-ssa/ssa-dse-26.c we now SRA the BIT_FIELD_REF
appearing there leading to more DSE, fully eliding the aggregates.

This results in the same false positive -Wuninitialized as the
older attempt to remove the folding from optimize_bit_field_compare,
fixed by initializing part of the aggregate unconditionally.

	PR tree-optimization/111779
gcc/
	* tree-sra.cc (sra_handled_bf_read_p): New function.
	(build_access_from_expr_1): Handle some BIT_FIELD_REFs.
	(sra_modify_expr): Likewise.
	(make_fancy_name_1): Skip over BIT_FIELD_REF.

gcc/fortran/
	* trans-expr.cc (gfc_trans_assignment_1): Initialize
	lhs_caf_attr and rhs_caf_attr codimension flag to avoid
	false positive -Wuninitialized.

gcc/testsuite/
	* gcc.dg/tree-ssa/ssa-dse-26.c: Adjust for more DSE.
	* gcc.dg/vect/vect-pr111779.c: New testcase.

gcc/fortran/trans-expr.cc

@@ -12015,7 +12015,10 @@ gfc_trans_assignment_1 (gfc_expr * expr1, gfc_expr * expr2, bool init_flag,
 		 && !is_runtime_conformable (expr1, expr2);
 
   /* Only analyze the expressions for coarray properties, when in coarray-lib
-     mode.  */
+     mode.  Avoid false-positive uninitialized diagnostics with initializing
+     the codimension flag unconditionally.  */
+  lhs_caf_attr.codimension = false;
+  rhs_caf_attr.codimension = false;
   if (flag_coarray == GFC_FCOARRAY_LIB)
     {
       lhs_caf_attr = gfc_caf_attr (expr1, false, &lhs_refs_comp);

gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-26.c

@@ -31,5 +31,5 @@ constraint_equal (struct constraint a, struct constraint b)
     && constraint_expr_equal (a.rhs, b.rhs);
 }
 
-/* { dg-final { scan-tree-dump-times "Deleted dead store: x = " 1 "dse1" } } */
-/* { dg-final { scan-tree-dump-times "Deleted dead store: y = " 1 "dse1" } } */
+/* { dg-final { scan-tree-dump-times "Deleted dead store: x = " 2 "dse1" } } */
+/* { dg-final { scan-tree-dump-times "Deleted dead store: y = " 2 "dse1" } } */

gcc/testsuite/gcc.dg/vect/vect-pr111779.c

@@ -0,0 +1,56 @@
+#include <stdbool.h>
+#include "tree-vect.h"
+
+struct C
+{
+    int c;
+    int d;
+    bool f :1;
+    float e;
+};
+
+struct A
+{
+  unsigned int a;
+  unsigned char c1, c2;
+  bool b1 : 1;
+  bool b2 : 1;
+  bool b3 : 1;
+  struct C b4;
+};
+
+void __attribute__((noipa))
+foo (const struct A * __restrict x, int y)
+{
+  int s = 0, i = 0;
+  for (i = 0; i < y; ++i)
+    {
+      const struct A a = x[i];
+      s += a.b4.f ? 1 : 0;
+    }
+  if (s != 0)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+  struct A x[100];
+  int i;
+
+  check_vect ();
+
+  __builtin_memset (x, -1, sizeof (x));
+#pragma GCC novect
+  for (i = 0; i < 100; i++)
+    {
+      x[i].b1 = false;
+      x[i].b2 = false;
+      x[i].b3 = false;
+      x[i].b4.f = false;
+    }
+  foo (x, 100);
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" { target vect_int } } } */

gcc/tree-sra.cc

@@ -1113,6 +1113,21 @@ disqualify_base_of_expr (tree t, const char *reason)
     disqualify_candidate (t, reason);
 }
 
+/* Return true if the BIT_FIELD_REF read EXPR is handled by SRA.  */
+
+static bool
+sra_handled_bf_read_p (tree expr)
+{
+  uint64_t size, offset;
+  if (bit_field_size (expr).is_constant (&size)
+      && bit_field_offset (expr).is_constant (&offset)
+      && size % BITS_PER_UNIT == 0
+      && offset % BITS_PER_UNIT == 0
+      && pow2p_hwi (size))
+    return true;
+  return false;
+}
+
 /* Scan expression EXPR and create access structures for all accesses to
    candidates for scalarization.  Return the created access or NULL if none is
    created.  */
@@ -1123,7 +1138,8 @@ build_access_from_expr_1 (tree expr, gimple *stmt, bool write)
   struct access *ret = NULL;
   bool partial_ref;
 
-  if (TREE_CODE (expr) == BIT_FIELD_REF
+  if ((TREE_CODE (expr) == BIT_FIELD_REF
+       && (write || !sra_handled_bf_read_p (expr)))
       || TREE_CODE (expr) == IMAGPART_EXPR
       || TREE_CODE (expr) == REALPART_EXPR)
     {
@@ -1170,6 +1186,7 @@ build_access_from_expr_1 (tree expr, gimple *stmt, bool write)
     case COMPONENT_REF:
     case ARRAY_REF:
     case ARRAY_RANGE_REF:
+    case BIT_FIELD_REF:
       ret = create_access (expr, stmt, write);
       break;
 
@@ -1549,6 +1566,7 @@ make_fancy_name_1 (tree expr)
       obstack_grow (&name_obstack, buffer, strlen (buffer));
       break;
 
+    case BIT_FIELD_REF:
     case ADDR_EXPR:
       make_fancy_name_1 (TREE_OPERAND (expr, 0));
       break;
@@ -1564,7 +1582,6 @@ make_fancy_name_1 (tree expr)
 	}
       break;
 
-    case BIT_FIELD_REF:
     case REALPART_EXPR:
     case IMAGPART_EXPR:
       gcc_unreachable (); 	/* we treat these as scalars.  */
@@ -3769,7 +3786,8 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator *gsi, bool write)
   tree type, bfr, orig_expr;
   bool partial_cplx_access = false;
 
-  if (TREE_CODE (*expr) == BIT_FIELD_REF)
+  if (TREE_CODE (*expr) == BIT_FIELD_REF
+      && (write || !sra_handled_bf_read_p (*expr)))
     {
       bfr = *expr;
       expr = &TREE_OPERAND (*expr, 0);