[035/nnn] poly_int: expand_debug_expr

[Richard Sandiford <richard.sandiford@linaro.org>]

This patch makes expand_debug_expr track polynomial memory offsets.
It simplifies the handling of the case in which the reference is not
to the first byte of the base, which seemed non-trivial enough to
make it worth splitting out as a separate patch.


2017-10-23  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* tree.h (get_inner_reference): Add a version that returns the
	offset and size as poly_int64_pods rather than HOST_WIDE_INTs.
	* cfgexpand.c (expand_debug_expr): Track polynomial offsets.  Simply
	the case in which bitpos is not associated with the first byte.

Index: gcc/tree.h
===================================================================
--- gcc/tree.h	2017-10-23 17:11:40.253962440 +0100
+++ gcc/tree.h	2017-10-23 17:18:40.711668346 +0100
@@ -5610,6 +5610,17 @@ extern bool complete_ctor_at_level_p (co
    the access position and size.  */
 extern tree get_inner_reference (tree, HOST_WIDE_INT *, HOST_WIDE_INT *,
 				 tree *, machine_mode *, int *, int *, int *);
+/* Temporary.  */
+inline tree
+get_inner_reference (tree exp, poly_int64_pod *pbitsize,
+		     poly_int64_pod *pbitpos, tree *poffset,
+		     machine_mode *pmode, int *punsignedp,
+		     int *preversep, int *pvolatilep)
+{
+  return get_inner_reference (exp, &pbitsize->coeffs[0], &pbitpos->coeffs[0],
+			      poffset, pmode, punsignedp, preversep,
+			      pvolatilep);
+}
 
 extern tree build_personality_function (const char *);
 
Index: gcc/cfgexpand.c
===================================================================
--- gcc/cfgexpand.c	2017-10-23 17:16:59.700268356 +0100
+++ gcc/cfgexpand.c	2017-10-23 17:18:40.711668346 +0100
@@ -4450,7 +4450,7 @@ expand_debug_expr (tree exp)
     case VIEW_CONVERT_EXPR:
       {
 	machine_mode mode1;
-	HOST_WIDE_INT bitsize, bitpos;
+	poly_int64 bitsize, bitpos;
 	tree offset;
 	int reversep, volatilep = 0;
 	tree tem
@@ -4458,7 +4458,7 @@ expand_debug_expr (tree exp)
 				 &unsignedp, &reversep, &volatilep);
 	rtx orig_op0;
 
-	if (bitsize == 0)
+	if (known_zero (bitsize))
 	  return NULL;
 
 	orig_op0 = op0 = expand_debug_expr (tem);
@@ -4501,19 +4501,14 @@ expand_debug_expr (tree exp)
 	    if (mode1 == VOIDmode)
 	      /* Bitfield.  */
 	      mode1 = smallest_int_mode_for_size (bitsize);
-	    if (bitpos >= BITS_PER_UNIT)
+	    poly_int64 bytepos = bits_to_bytes_round_down (bitpos);
+	    if (maybe_nonzero (bytepos))
 	      {
-		op0 = adjust_address_nv (op0, mode1, bitpos / BITS_PER_UNIT);
-		bitpos %= BITS_PER_UNIT;
+		op0 = adjust_address_nv (op0, mode1, bytepos);
+		bitpos = num_trailing_bits (bitpos);
 	      }
-	    else if (bitpos < 0)
-	      {
-		HOST_WIDE_INT units
-		  = (-bitpos + BITS_PER_UNIT - 1) / BITS_PER_UNIT;
-		op0 = adjust_address_nv (op0, mode1, -units);
-		bitpos += units * BITS_PER_UNIT;
-	      }
-	    else if (bitpos == 0 && bitsize == GET_MODE_BITSIZE (mode))
+	    else if (known_zero (bitpos)
+		     && must_eq (bitsize, GET_MODE_BITSIZE (mode)))
 	      op0 = adjust_address_nv (op0, mode, 0);
 	    else if (GET_MODE (op0) != mode1)
 	      op0 = adjust_address_nv (op0, mode1, 0);
@@ -4524,17 +4519,18 @@ expand_debug_expr (tree exp)
 	    set_mem_attributes (op0, exp, 0);
 	  }
 
-	if (bitpos == 0 && mode == GET_MODE (op0))
+	if (known_zero (bitpos) && mode == GET_MODE (op0))
 	  return op0;
 
-        if (bitpos < 0)
+	if (may_lt (bitpos, 0))
           return NULL;
 
 	if (GET_MODE (op0) == BLKmode)
 	  return NULL;
 
-	if ((bitpos % BITS_PER_UNIT) == 0
-	    && bitsize == GET_MODE_BITSIZE (mode1))
+	poly_int64 bytepos;
+	if (multiple_p (bitpos, BITS_PER_UNIT, &bytepos)
+	    && must_eq (bitsize, GET_MODE_BITSIZE (mode1)))
 	  {
 	    machine_mode opmode = GET_MODE (op0);
 
@@ -4547,12 +4543,11 @@ expand_debug_expr (tree exp)
 	       debug stmts).  The gen_subreg below would rightfully
 	       crash, and the address doesn't really exist, so just
 	       drop it.  */
-	    if (bitpos >= GET_MODE_BITSIZE (opmode))
+	    if (must_ge (bitpos, GET_MODE_BITSIZE (opmode)))
 	      return NULL;
 
-	    if ((bitpos % GET_MODE_BITSIZE (mode)) == 0)
-	      return simplify_gen_subreg (mode, op0, opmode,
-					  bitpos / BITS_PER_UNIT);
+	    if (multiple_p (bitpos, GET_MODE_BITSIZE (mode)))
+	      return simplify_gen_subreg (mode, op0, opmode, bytepos);
 	  }
 
 	return simplify_gen_ternary (SCALAR_INT_MODE_P (GET_MODE (op0))
@@ -4562,7 +4557,8 @@ expand_debug_expr (tree exp)
 				     GET_MODE (op0) != VOIDmode
 				     ? GET_MODE (op0)
 				     : TYPE_MODE (TREE_TYPE (tem)),
-				     op0, GEN_INT (bitsize), GEN_INT (bitpos));
+				     op0, gen_int_mode (bitsize, word_mode),
+				     gen_int_mode (bitpos, word_mode));
       }
 
     case ABS_EXPR: