try multi dest registers in default_zero_call_used_regs

[Alexandre Oliva <oliva@adacore.com>]

When the mode of regno_reg_rtx is not hard_regno_mode_ok for the
target, try grouping the register with subsequent ones.  This enables
s16 to s31 and their hidden pairs to be zeroed with the default logic
on some arm variants.

Regstrapped on x86_64-linux-gnu, also tested on an affected arm
configuration.  Ok to install?


for  gcc/ChangeLog

	* targhooks.c (default_zero_call_used_regs): Attempt to group
	regs that the target refuses to use in their natural modes.
---
 gcc/targhooks.cc |   79 ++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 70 insertions(+), 9 deletions(-)

diff --git a/gcc/targhooks.cc b/gcc/targhooks.cc
index fc49235eb38ee..bdaab9c63c7ee 100644
--- a/gcc/targhooks.cc
+++ b/gcc/targhooks.cc
@@ -1035,16 +1035,45 @@ default_zero_call_used_regs (HARD_REG_SET need_zeroed_hardregs)
     if (TEST_HARD_REG_BIT (need_zeroed_hardregs, regno))
       {
 	rtx_insn *last_insn = get_last_insn ();
-	machine_mode mode = GET_MODE (regno_reg_rtx[regno]);
+	rtx regno_rtx = regno_reg_rtx[regno];
+	machine_mode mode = GET_MODE (regno_rtx);
+
+	/* If the natural mode doesn't work, try some wider mode.  */
+	if (!targetm.hard_regno_mode_ok (regno, mode))
+	  {
+	    for (int nregs = 2;
+		 regno + nregs <= FIRST_PSEUDO_REGISTER
+		   && TEST_HARD_REG_BIT (need_zeroed_hardregs,
+					 regno + nregs - 1);
+		 nregs++)
+	      {
+		mode = choose_hard_reg_mode (regno, nregs, 0);
+		if (mode == E_VOIDmode)
+		  continue;
+		gcc_checking_assert (targetm.hard_regno_mode_ok (regno, mode));
+		regno_rtx = gen_rtx_REG (mode, regno);
+		break;
+	      }
+	    if (mode != GET_MODE (regno_rtx)
+		|| regno_rtx == regno_reg_rtx[regno])
+	      {
+		SET_HARD_REG_BIT (failed, regno);
+		continue;
+	      }
+	  }
+
 	rtx zero = CONST0_RTX (mode);
-	rtx_insn *insn = emit_move_insn (regno_reg_rtx[regno], zero);
+	rtx_insn *insn = emit_move_insn (regno_rtx, zero);
 	if (!valid_insn_p (insn))
 	  {
 	    SET_HARD_REG_BIT (failed, regno);
 	    delete_insns_since (last_insn);
 	  }
 	else
-	  progress = true;
+	  {
+	    progress = true;
+	    regno += hard_regno_nregs (regno, mode) - 1;
+	  }
       }
 
   /* Now retry with copies from zeroed registers, as long as we've
@@ -1060,7 +1089,34 @@ default_zero_call_used_regs (HARD_REG_SET need_zeroed_hardregs)
       for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
 	if (TEST_HARD_REG_BIT (retrying, regno))
 	  {
-	    machine_mode mode = GET_MODE (regno_reg_rtx[regno]);
+	    rtx regno_rtx = regno_reg_rtx[regno];
+	    machine_mode mode = GET_MODE (regno_rtx);
+
+	    /* If the natural mode doesn't work, try some wider mode.  */
+	    if (!targetm.hard_regno_mode_ok (regno, mode))
+	      {
+		for (int nregs = 2;
+		     regno + nregs <= FIRST_PSEUDO_REGISTER
+		       && TEST_HARD_REG_BIT (need_zeroed_hardregs,
+					     regno + nregs - 1);
+		     nregs++)
+		  {
+		    mode = choose_hard_reg_mode (regno, nregs, 0);
+		    if (mode == E_VOIDmode)
+		      continue;
+		    gcc_checking_assert (targetm.hard_regno_mode_ok (regno,
+								     mode));
+		    regno_rtx = gen_rtx_REG (mode, regno);
+		    break;
+		  }
+		if (mode != GET_MODE (regno_rtx)
+		    || regno_rtx == regno_reg_rtx[regno])
+		  {
+		    SET_HARD_REG_BIT (failed, regno);
+		    continue;
+		  }
+	      }
+	    
 	    bool success = false;
 	    /* Look for a source.  */
 	    for (unsigned int src = 0; src < FIRST_PSEUDO_REGISTER; src++)
@@ -1086,8 +1142,10 @@ default_zero_call_used_regs (HARD_REG_SET need_zeroed_hardregs)
 
 		/* SRC is usable, try to copy from it.  */
 		rtx_insn *last_insn = get_last_insn ();
-		rtx zsrc = gen_rtx_REG (mode, src);
-		rtx_insn *insn = emit_move_insn (regno_reg_rtx[regno], zsrc);
+		rtx src_rtx = (mode == GET_MODE (regno_reg_rtx[src])
+			       ? regno_reg_rtx[src]
+			       : gen_rtx_REG (mode, src));
+		rtx_insn *insn = emit_move_insn (regno_rtx, src_rtx);
 		if (!valid_insn_p (insn))
 		  /* It didn't work, remove any inserts.  We'll look
 		     for another SRC.  */
@@ -1100,13 +1158,16 @@ default_zero_call_used_regs (HARD_REG_SET need_zeroed_hardregs)
 		  }
 	      }
 
-	    /* If nothing worked for REGNO this round, marked it to be
+	    /* If nothing worked for REGNO this round, mark it to be
 	       retried if we get another round.  */
 	    if (!success)
 	      SET_HARD_REG_BIT (failed, regno);
 	    else
-	      /* Take note so as to enable another round if needed.  */
-	      progress = true;
+	      {
+		/* Take note so as to enable another round if needed.  */
+		progress = true;
+		regno += hard_regno_nregs (regno, mode) - 1;
+	      }
 	  }
     }
 


-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
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but very few check the facts.  Ask me about <https://stallmansupport.org>