rs6000.md (cmpmemsi): New define_expand.

	* config/rs6000/rs6000.md (cmpmemsi): New define_expand.
	* config/rs6000/rs6000.c (expand_block_compare): New function used by
	cmpmemsi pattern to do builtin expansion of memcmp ().
	(compute_current_alignment): Add helper function for
	expand_block_compare used to compute alignment as the compare proceeds.
	(select_block_compare_mode): Used by expand_block_compare to select
	the mode used for reading the next chunk of bytes in the compare.
	(do_load_for_compare): Used by expand_block_compare to emit the load
	insns for the compare.
	(rs6000_emit_dot_insn): Moved this function to avoid a forward
	reference from expand_block_compare ().
	* config/rs6000/rs6000-protos.h (expand_block_compare): Add a
	prototype for this function.
	* config/rs6000/rs6000.opt (mblock-compare-inline-limit): Add a new
	target option for controlling how much code inline expansion of
	memcmp() will be allowed to generate.

From-SVN: r240455

gcc/config/rs6000/rs6000-protos.h

@@ -77,6 +77,7 @@ extern void rs6000_expand_interleave (rtx, rtx, rtx, bool);
 extern void rs6000_scale_v2df (rtx, rtx, int);
 extern int expand_block_clear (rtx[]);
 extern int expand_block_move (rtx[]);
+extern bool expand_block_compare (rtx[]);
 extern const char * rs6000_output_load_multiple (rtx[]);
 extern bool rs6000_is_valid_mask (rtx, int *, int *, machine_mode);
 extern bool rs6000_is_valid_and_mask (rtx, machine_mode);

gcc/config/rs6000/rs6000.md

@@ -8614,6 +8614,27 @@
     FAIL;
 }")
 
+;; String/block compare insn.
+;; Argument 0 is the target (result)
+;; Argument 1 is the destination
+;; Argument 2 is the source
+;; Argument 3 is the length
+;; Argument 4 is the alignment
+
+(define_expand "cmpmemsi"
+  [(parallel [(set (match_operand:SI 0)
+               (compare:SI (match_operand:BLK 1)
+                           (match_operand:BLK 2)))
+	      (use (match_operand:SI 3))
+	      (use (match_operand:SI 4))])]
+  ""
+{
+  if (expand_block_compare (operands))
+    DONE;
+  else	
+    FAIL;
+})
+
 ;; String/block move insn.
 ;; Argument 0 is the destination
 ;; Argument 1 is the source

gcc/config/rs6000/rs6000.opt

@@ -333,6 +333,10 @@ mblock-move-inline-limit=
 Target Report Var(rs6000_block_move_inline_limit) Init(0) RejectNegative Joined UInteger Save
 Specify how many bytes should be moved inline before calling out to memcpy/memmove.
 
+mblock-compare-inline-limit=
+Target Report Var(rs6000_block_compare_inline_limit) Init(5) RejectNegative Joined UInteger Save
+Specify the maximum number pairs of load instructions that should be generated inline for the compare.  If the number needed exceeds the limit, a call to memcmp will be generated instead.
+
 misel
 Target Report Mask(ISEL) Var(rs6000_isa_flags)
 Generate isel instructions.