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Re: nop in load-delay-slot (on MIPS o32 PIC code)

From: Atsushi Nemoto <anemo at mba dot ocn dot ne dot jp>
To: ica2_ts at csv dot ica dot uni-stuttgart dot de
Cc: binutils at sources dot redhat dot com
Date: Thu, 22 Apr 2004 11:32:03 +0900 (JST)
Subject: Re: nop in load-delay-slot (on MIPS o32 PIC code)
References: <yov5d662cy9w.fsf@ldt-sj3-010.sj.broadcom.com><20040421.183639.32341709.nemoto@toshiba-tops.co.jp><20040421153520.GW6736@rembrandt.csv.ica.uni-stuttgart.de>

>>>>> On Wed, 21 Apr 2004 17:35:20 +0200, Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de> said:
>> I created a patch against 040420 snapshot (see attached).  Not so
>> big.  Could you review it?

ica2_ts> It seems like you missed a few ones, at lines 4006 and
ica2_ts> 6216. Any yes, wrapping it in a, say, load_delay_nop()
ica2_ts> function would also be better.

Thank you.  I looked codes more closely.  The lines 4006 and 6216 (and
also 5345, 5677) are already covered by reg_needs_delay() and should
not be changed. (these lines are immediate after relax_switch() so we
can not assume this is really a load delay slot, is this right?)

Here is a revised patch.

diff -ur binutils-040420.org/gas/config/tc-mips.c binutils-040420/gas/config/tc-mips.c
--- binutils-040420.org/gas/config/tc-mips.c	Tue Apr 20 06:08:43 2004
+++ binutils-040420/gas/config/tc-mips.c	Thu Apr 22 11:00:25 2004
@@ -3789,6 +3789,13 @@
     macro_build (&lo32, "ori", "t,r,i", reg, freg, BFD_RELOC_LO16);
 }
 
+static inline void
+load_delay_nop (void)
+{
+  if (!gpr_interlocks)
+    macro_build (NULL, "nop", "");
+}
+
 /* Load an address into a register.  */
 
 static void
@@ -3922,7 +3929,7 @@
 	  ep->X_add_number = 0;
 	  macro_build (ep, ADDRESS_LOAD_INSN, "t,o(b)", reg,
 		       BFD_RELOC_MIPS_GOT16, mips_gp_register);
-	  macro_build (NULL, "nop", "");
+	  load_delay_nop ();
 	  relax_start (ep->X_add_symbol);
 	  relax_switch ();
 	  macro_build (ep, ADDRESS_ADDI_INSN, "t,r,j", reg, reg,
@@ -4007,7 +4014,7 @@
 	    }
 	  macro_build (ep, ADDRESS_LOAD_INSN, "t,o(b)", reg,
 		       BFD_RELOC_MIPS_GOT16, mips_gp_register);
-	  macro_build (NULL, "nop", "");
+	  load_delay_nop ();
 	  macro_build (ep, ADDRESS_ADDI_INSN, "t,r,j", reg, reg,
 		       BFD_RELOC_LO16);
 	  relax_end ();
@@ -5069,12 +5076,12 @@
 		  /* We're going to put in an addu instruction using
 		     tempreg, so we may as well insert the nop right
 		     now.  */
-		  macro_build (NULL, "nop", "");
+		  load_delay_nop ();
 		}
 	      relax_switch ();
 	      macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)",
 			   tempreg, BFD_RELOC_MIPS_GOT16, mips_gp_register);
-	      macro_build (NULL, "nop", "");
+	      load_delay_nop ();
 	      macro_build (&offset_expr, ADDRESS_ADDI_INSN, "t,r,j",
 			   tempreg, tempreg, BFD_RELOC_LO16);
 	      relax_end ();
@@ -5086,7 +5093,7 @@
 		   && offset_expr.X_add_number < 0x8000)
 	    {
 	      load_got_offset (tempreg, &offset_expr);
-	      macro_build (NULL, "nop", "");
+	      load_delay_nop ();
 	      add_got_offset (tempreg, &offset_expr);
 	    }
 	  else
@@ -5105,7 +5112,7 @@
 		 not using a base register.  */
 	      if (breg == treg)
 		{
-		  macro_build (NULL, "nop", "");
+		  load_delay_nop ();
 		  macro_build (NULL, ADDRESS_ADD_INSN, "d,v,t",
 			       treg, AT, breg);
 		  breg = 0;
@@ -5288,13 +5295,13 @@
 		  /* We're going to put in an addu instruction using
 		     tempreg, so we may as well insert the nop right
 		     now.  */
-		  macro_build (NULL, "nop", "");
+		  load_delay_nop ();
 		}
 	    }
 	  else if (expr1.X_add_number >= -0x8000
 		   && expr1.X_add_number < 0x8000)
 	    {
-	      macro_build (NULL, "nop", "");
+	      load_delay_nop ();
 	      macro_build (&expr1, ADDRESS_ADDI_INSN, "t,r,j",
 			   tempreg, tempreg, BFD_RELOC_LO16);
 	    }
@@ -5314,7 +5321,7 @@
 	      else
 		{
 		  assert (tempreg == AT);
-		  macro_build (NULL, "nop", "");
+		  load_delay_nop ();
 		  macro_build (NULL, ADDRESS_ADD_INSN, "d,v,t",
 			       treg, AT, breg);
 		  dreg = treg;
@@ -5341,7 +5348,7 @@
 	  if (expr1.X_add_number >= -0x8000
 	      && expr1.X_add_number < 0x8000)
 	    {
-	      macro_build (NULL, "nop", "");
+	      load_delay_nop ();
 	      macro_build (&offset_expr, ADDRESS_ADDI_INSN, "t,r,j",
 			   tempreg, tempreg, BFD_RELOC_LO16);
 	      /* FIXME: If add_number is 0, and there was no base
@@ -5357,7 +5364,7 @@
 		  /* We must add in the base register now, as in the
 		     external symbol case.  */
 		  assert (tempreg == AT);
-		  macro_build (NULL, "nop", "");
+		  load_delay_nop ();
 		  macro_build (NULL, ADDRESS_ADD_INSN, "d,v,t",
 			       treg, AT, breg);
 		  tempreg = treg;
@@ -5643,7 +5650,7 @@
 		  macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)",
 			       PIC_CALL_REG, BFD_RELOC_MIPS_CALL16,
 			       mips_gp_register);
-		  macro_build (NULL, "nop", "");
+		  load_delay_nop ();
 		  relax_switch ();
 		}
 	      else
@@ -5658,7 +5665,7 @@
 		  macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)",
 			       PIC_CALL_REG, BFD_RELOC_MIPS_CALL_LO16,
 			       PIC_CALL_REG);
-		  macro_build (NULL, "nop", "");
+		  load_delay_nop ();
 		  relax_switch ();
 		  if (gpdelay)
 		    macro_build (NULL, "nop", "");
@@ -5666,7 +5673,7 @@
 	      macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)",
 			   PIC_CALL_REG, BFD_RELOC_MIPS_GOT16,
 			   mips_gp_register);
-	      macro_build (NULL, "nop", "");
+	      load_delay_nop ();
 	      macro_build (&offset_expr, ADDRESS_ADDI_INSN, "t,r,j",
 			   PIC_CALL_REG, PIC_CALL_REG, BFD_RELOC_LO16);
 	      relax_end ();
@@ -6166,7 +6173,7 @@
 	    as_bad (_("PIC code offset overflow (max 16 signed bits)"));
 	  macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)", tempreg,
 		       lw_reloc_type, mips_gp_register);
-	  macro_build (NULL, "nop", "");
+	  load_delay_nop ();
 	  relax_start (offset_expr.X_add_symbol);
 	  relax_switch ();
 	  macro_build (&offset_expr, ADDRESS_ADDI_INSN, "t,r,j", tempreg,
@@ -6216,7 +6223,7 @@
 	    macro_build (NULL, "nop", "");
 	  macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)", tempreg,
 		       BFD_RELOC_MIPS_GOT16, mips_gp_register);
-	  macro_build (NULL, "nop", "");
+	  load_delay_nop ();
 	  macro_build (&offset_expr, ADDRESS_ADDI_INSN, "t,r,j", tempreg,
 		       tempreg, BFD_RELOC_LO16);
 	  relax_end ();
@@ -6691,7 +6698,7 @@
 	      || expr1.X_add_number >= 0x8000 - 4)
 	    as_bad (_("PIC code offset overflow (max 16 signed bits)"));
 	  load_got_offset (AT, &offset_expr);
-	  macro_build (NULL, "nop", "");
+	  load_delay_nop ();
 	  if (breg != 0)
 	    macro_build (NULL, ADDRESS_ADD_INSN, "d,v,t", AT, breg, AT);
 
@@ -6750,7 +6757,7 @@
 		       AT, AT, mips_gp_register);
 	  macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)",
 		       AT, BFD_RELOC_MIPS_GOT_LO16, AT);
-	  macro_build (NULL, "nop", "");
+	  load_delay_nop ();
 	  if (breg != 0)
 	    macro_build (NULL, ADDRESS_ADD_INSN, "d,v,t", AT, breg, AT);
 	  /* Itbl support may require additional care here.  */
@@ -6774,7 +6781,7 @@
 	    macro_build (NULL, "nop", "");
 	  macro_build (&offset_expr, ADDRESS_LOAD_INSN, "t,o(b)", AT,
 		       BFD_RELOC_MIPS_GOT16, mips_gp_register);
-	  macro_build (NULL, "nop", "");
+	  load_delay_nop ();
 	  if (breg != 0)
 	    macro_build (NULL, ADDRESS_ADD_INSN, "d,v,t", AT, breg, AT);
 	  /* Itbl support may require additional care here.  */
---
Atsushi Nemoto

Follow-Ups:
- Re: nop in load-delay-slot (on MIPS o32 PIC code)
  - From: Thiemo Seufer

References:
- Re: nop in load-delay-slot (on MIPS o32 PIC code)
  - From: cgd
- Re: nop in load-delay-slot (on MIPS o32 PIC code)
  - From: Atsushi Nemoto
- Re: nop in load-delay-slot (on MIPS o32 PIC code)
  - From: Thiemo Seufer

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