[PATCH][2/2][i386] STV changes, reg-copy as vector

[Richard Biener <rguenther at suse dot de>]

The following splits out the change that makes the live-range split /
mode change copy pseudos vector mode pseudos.  I've tried reproducing
the issue I faced with SImode chains but failed likely because we're
never using simple moves in the end while for SImode we can end up
with

(set (subreg:V4SI (reg:SI 42) 0) (subreg:V4SI (reg:SI 41) 0))

which we happily propagate out.  So pursuing this patch independently
doesn't make much sense.  Still the main change is in
dimode_scalar_chain::make_vector_copies where 'vreg' is now V2DImode
instead of DImode and the change to emit_move_insn (vreg, tmp)
hints at the change done to the above problematic insn.

The rest of the changes deal with some regs already being in
the appropriate vector mode.

I realize I might have avoided my original issue by emitting not
the above reg-reg move but

 (set (subreg:V4SI (reg:SI 42) 0)
   (vec_merge:V4SI
      (vec_duplicate:V4SI (reg:SI 41))
      (const_vec [0 0 0 0])
      (const_1)))

but I didn't try (the full patch contained a testcase for the
issue).  Still it seems odd to use DImode pseudos when all uses
are wrapped in (subreg:V2DI ...).

As (unrelated) change I propose to error with fatal_insn_not_found
in case recog doesn't recognize the altered insns which make it
easier to spot errors early.

Bootstrap / regtest running on x86_64-unknown-linux-gnu ontop of [1/2], OK 
for trunk if that succeeds?

Thanks,
Richard.

2019-08-13  Richard Biener  <rguenther@suse.de>

	* config/i386/i386-features.c
	(dimode_scalar_chain::replace_with_subreg): Elide the subreg if the
	reg is already vector.
	(dimode_scalar_chain::convert_op): Likewise.
	(dimode_scalar_chain::make_vector_copies): Use a vector-mode pseudo as
	destination to avoid later passes copy-propagating it out.
	(dimode_chain::convert_insn): Convert the source of a
	memory op in case it is not of the appropriate scalar mode.
	Raise fatal_insn_not_found if the converted insn is not recognized.

Index: gcc/config/i386/i386-features.c
===================================================================
--- gcc/config/i386/i386-features.c	(revision 274328)
+++ gcc/config/i386/i386-features.c	(working copy)
@@ -573,7 +573,8 @@ rtx
 dimode_scalar_chain::replace_with_subreg (rtx x, rtx reg, rtx new_reg)
 {
   if (x == reg)
-    return gen_rtx_SUBREG (V2DImode, new_reg, 0);
+    return (GET_MODE (new_reg) == V2DImode
+	    ? new_reg : gen_rtx_SUBREG (V2DImode, new_reg, 0));
 
   const char *fmt = GET_RTX_FORMAT (GET_CODE (x));
   int i, j;
@@ -627,7 +628,7 @@ void
 dimode_scalar_chain::make_vector_copies (unsigned regno)
 {
   rtx reg = regno_reg_rtx[regno];
-  rtx vreg = gen_reg_rtx (DImode);
+  rtx vreg = gen_reg_rtx (V2DImode);
   df_ref ref;
 
   for (ref = DF_REG_DEF_CHAIN (regno); ref; ref = DF_REF_NEXT_REG (ref))
@@ -641,7 +642,12 @@ dimode_scalar_chain::make_vector_copies
 			    gen_rtx_SUBREG (SImode, reg, 0));
 	    emit_move_insn (adjust_address (tmp, SImode, 4),
 			    gen_rtx_SUBREG (SImode, reg, 4));
-	    emit_move_insn (vreg, tmp);
+	    emit_move_insn (vreg,
+			    gen_rtx_VEC_MERGE (V2DImode,
+					       gen_rtx_VEC_DUPLICATE (V2DImode,
+								      tmp),
+					       CONST0_RTX (V2DImode),
+					       GEN_INT (HOST_WIDE_INT_1U)));
 	  }
 	else if (TARGET_SSE4_1)
 	  {
@@ -841,7 +847,8 @@ dimode_scalar_chain::convert_op (rtx *op
 	    gcc_assert (!DF_REF_CHAIN (ref));
 	    break;
 	  }
-      *op = gen_rtx_SUBREG (V2DImode, *op, 0);
+      if (GET_MODE (*op) != V2DImode)
+	*op = gen_rtx_SUBREG (V2DImode, *op, 0);
     }
   else if (CONST_INT_P (*op))
     {
@@ -931,6 +938,8 @@ dimode_scalar_chain::convert_insn (rtx_i
     case MEM:
       if (!REG_P (dst))
 	convert_op (&src, insn);
+      else if (GET_MODE (src) != DImode)
+	src = gen_rtx_SUBREG (DImode, src, 0);
       break;
 
     case REG:
@@ -977,7 +986,9 @@ dimode_scalar_chain::convert_insn (rtx_i
   PATTERN (insn) = def_set;
 
   INSN_CODE (insn) = -1;
-  recog_memoized (insn);
+  int patt = recog_memoized (insn);
+  if (patt == -1)
+    fatal_insn_not_found (insn);
   df_insn_rescan (insn);
 }