[PATCH] V11 patch #2 of 15, Use prefixed load for vector extract with large offset

[Michael Meissner <meissner@linux.ibm.com>]

This patch incorporates large offsets for -mcpu=future when we optimization a
vector extract from memory and the memory address previously had been a
prefixed address with a large offset.

The current code would generate loading up the constant into a temporary and
then doing an indexed load.  Successive passes would eventually optimize that
back into the form we want (having the base register plus a large offset), but
it is better to generate the optimial code sooner.

I have bootstrapped this change on a little endian power8 system and there were
no regressions.  Can I check this into the trunk?

2019-12-20  Michael Meissner  <meissner@linux.ibm.com>

	* config/rs6000/rs6000.c (rs6000_adjust_vec_address): Add support
	for the offset being 34-bits when -mcpu=future is used.

Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c	(revision 279553)
+++ gcc/config/rs6000/rs6000.c	(working copy)
@@ -6792,9 +6792,17 @@ rs6000_adjust_vec_address (rtx scalar_re
 	  HOST_WIDE_INT offset = INTVAL (op1) + INTVAL (element_offset);
 	  rtx offset_rtx = GEN_INT (offset);
 
-	  if (IN_RANGE (offset, -32768, 32767)
+	  /* 16-bit offset.  */
+	  if (SIGNED_INTEGER_16BIT_P (offset)
 	      && (scalar_size < 8 || (offset & 0x3) == 0))
 	    new_addr = gen_rtx_PLUS (Pmode, op0, offset_rtx);
+
+	  /* 34-bit offset if we have prefixed addresses.  */
+	  else if (TARGET_PREFIXED_ADDR && SIGNED_INTEGER_34BIT_P (offset))
+	    new_addr = gen_rtx_PLUS (Pmode, op0, offset_rtx);
+
+	  /* Offset overflowed, move offset to the temporary (which will likely
+	     be split), and do X-FORM addressing.  */
 	  else
 	    {
 	      emit_move_insn (base_tmp, offset_rtx);
@@ -6825,6 +6833,12 @@ rs6000_adjust_vec_address (rtx scalar_re
 	      emit_insn (insn);
 	    }
 
+	  /* Make sure we don't overwrite the temporary if the element being
+	     extracted is variable, and we've put the offset into base_tmp
+	     previously.  */
+	  else if (rtx_equal_p (base_tmp, element_offset))
+	    emit_insn (gen_add2_insn (base_tmp, op1));
+
 	  else
 	    {
 	      /* Make sure base_tmp is not the same as element_offset.  This

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.ibm.com, phone: +1 (978) 899-4797