rtl.def (SUBREG): Update comments.

gcc/
	* rtl.def (SUBREG): Update comments.
	* rtl.h (reg_attrs): Be explicit about the type of offset used.
	(set_reg_attrs_from_mem): Rename to...
	(set_reg_attrs_from_value): ...this.
	(adjust_reg_mode, byte_lowpart_offset): Declare.
	* emit-rtl.c (byte_lowpart_offset): New function.
	(update_reg_offset): Remove special offset handling for big-endian
	targets.
	(gen_rtx_REG_offset, gen_reg_rtx_offset): Explicitly say that the
	offset parameter is added to REG_OFFSET.
	(adjust_reg_mode): New function.
	(set_reg_attrs_for_mem): Rename to...
	(set_reg_attrs_for_value): ...this and generalize to all values.
	If the register is a lowpart of the value, adjust the offset
	accordingly.
	(set_reg_attrs_for_parm): Update after the above renaming.
	(set_reg_attrs_for_decl_rtl): New function, split out from
	set_decl_incoming_rtl.  Set the offset of plain REGs to the
	offset of the REG's mode from the decl's.  Assert that all
	subregs are lowparts and handle their inner registers in the
	same way as plain REGs.
	(set_decl_rtl, set_incoming_decl_rtl): Use reg_attrs_for_decl_rtl.
	(subreg_lowpart_offset): Explicitly say that the returned offset
	is a SUBREG_BYTE.
	* combine.c (do_SUBST_MODE, try_combine, undo_all): Use adjust_reg_mode
	instead of PUT_MODE.
	* final.c (alter_subreg): Fix/update argument to gen_rtx_REG_offset.
	* config/ia64/ia64.c (ia64_expand_load_address): Likewise.
	* regclass.c (reg_scan_mark_refs): Use set_reg_attrs_from_value.
	* reload.c (find_reloads_subreg_address): Call set_mem_offset
	when offseting a MEM.
	* var-tracking.c (offset_valid_for_tracked_p): Delete.
	(mode_for_reg_attrs): Replace with...
	(track_loc_p): ...this new function.  Return the mode and offset
	to the caller, checking that the latter is valid.  If the rtx is
	a paradoxical lowpart of the decl, use the decl's mode instead.
	Do the same when storing to a register that contains the entire decl.
	(var_lowpart): Use byte_lowpart_offset rather than
	subreg_lowpart_offset when adjusting the offset attribute.
	(count_uses, add_uses, add_stores): Use track_reg_p instead of
	REG_EXPR, MEM_EXPR, REG_OFFSET, INT_MEM_OFFSET, track_expr_p,
	offset_valid_for_tracked_p and mode_for_reg_attrs.  Generate
	lowparts for MEMs as well as REGs.
	(vt_add_function_parameters): When obtaining the information from
	the decl_rtl, adjust the offset to match incoming.  Use track_loc_p
	and var_lowpart.

From-SVN: r131055

1 files changed, 9 insertions, 2 deletions

diff --git a/gcc/final.c b/gcc/final.c
index 654f847..72edbc0 100644
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -2763,8 +2763,15 @@ alter_subreg (rtx *xp)
       else if (REG_P (y))
 	{
 	  /* Simplify_subreg can't handle some REG cases, but we have to.  */
-	  unsigned int regno = subreg_regno (x);
-	  *xp = gen_rtx_REG_offset (y, GET_MODE (x), regno, SUBREG_BYTE (x));
+	  unsigned int regno;
+	  HOST_WIDE_INT offset;
+
+	  regno = subreg_regno (x);
+	  if (subreg_lowpart_p (x))
+	    offset = byte_lowpart_offset (GET_MODE (x), GET_MODE (y));
+	  else
+	    offset = SUBREG_BYTE (x);
+	  *xp = gen_rtx_REG_offset (y, GET_MODE (x), regno, offset);
 	}
     }