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[PATCH] MIPS/GAS: Don't use $zero for address calculation

From: "Maciej W. Rozycki" <macro at codesourcery dot com>
To: <binutils at sourceware dot org>
Cc: Richard Sandiford <rdsandiford at googlemail dot com>
Date: Tue, 28 May 2013 19:29:59 +0100
Subject: [PATCH] MIPS/GAS: Don't use $zero for address calculation
Hi,

 Here's a fix to make GAS refrain from using $zero for address calculation 
in macros like:

	lw	$0, 0x12345678($2)

that expand to code like:

	lui	$0, 0x1234
	addu	$0, $2
	lw	$0, 22136($0)

that is not functionally equivalent.  With the change applied:

	lui	$1, 0x1234
	addu	$1, $2
	lw	$0, 22136($1)

is produced instead (subject to the usual .set at rules).  This is covered 
for the various macros affected by the test cases included.  Some variants 
are used to handle the overloaded LD macro in its 64-bit rather than 
32-bit mode that is inferred from the ABI on ELF targets and the ISA on 
ECOFF targets.

 No regressions in testing for the usual MIPS targets, OK to apply?

2013-05-28  Chao-ying Fu  <Chao-ying.Fu@imgtec.com>

	gas/
	* config/tc-mips.c (macro) <ld>: Don't use $zero for address 
	calculation.

2013-05-28  Maciej W. Rozycki  <macro@codesourcery.com>

	gas/testsuite/
	* gas/mips/ld-zero.d: New test.
	* gas/mips/ld-zero-2.d: New test.
	* gas/mips/ld-zero-3.d: New test.
	* gas/mips/ld-zero-q.d: New test.
	* gas/mips/ld-zero-u.d: New test.
	* gas/mips/ecoff@ld-zero-3.d: New test.
	* gas/mips/micromips@ld-zero-2.d: New test.
	* gas/mips/micromips@ld-zero-3.d: New test.
	* gas/mips/ld-zero.s: New test source.
	* gas/mips/ld-zero-2.s: New test source.
	* gas/mips/ld-zero-3.s: New test source.
	* gas/mips/ld-zero-q.s: New test source.
	* gas/mips/ld-zero-u.s: New test source.
	* gas/mips/mips.exp: Run the new tests.

  Maciej

binutils-mips-gas-tempreg-zero.diff
Index: binutils-fsf-trunk-quilt/gas/config/tc-mips.c
===================================================================
--- binutils-fsf-trunk-quilt.orig/gas/config/tc-mips.c	2013-05-26 13:50:08.000000000 +0100
+++ binutils-fsf-trunk-quilt/gas/config/tc-mips.c	2013-05-28 17:17:00.903796118 +0100
@@ -8286,7 +8286,8 @@ macro (struct mips_cl_insn *ip)
       goto ld_st;
 
     ld:
-      if (breg == treg + lp)
+      /* We don't want to use $0 as tempreg.  */
+      if ((breg == treg + lp) || (treg + lp == ZERO))
 	goto ld_st;
       else
 	tempreg = treg + lp;
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ecoff@ld-zero-3.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ecoff@ld-zero-3.d	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,4 @@
+#objdump: -dr --prefix-addresses
+#name: MIPS III load $zero
+#source: ld-zero-3.s
+#dump: ld-zero-3.d
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-2.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-2.d	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,11 @@
+#objdump: -dr --prefix-addresses
+#as: -32
+#name: MIPS II load $zero
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> ll	zero,22136\(at\)
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-2.s
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-2.s	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,7 @@
+	.text
+foo:
+	ll	$0, 0x12345678($2)
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-3.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-3.d	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,17 @@
+#objdump: -dr --prefix-addresses
+#as: -mabi=o64
+#name: MIPS III load $zero
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lwu	zero,22136\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> ld	zero,22136\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lld	zero,22136\(at\)
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-3.s
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-3.s	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,9 @@
+	.text
+foo:
+	lwu	$0, 0x12345678($2)
+	ld	$0, 0x12345678($2)
+	lld	$0, 0x12345678($2)
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-q.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-q.d	2013-05-28 17:41:18.593800871 +0100
@@ -0,0 +1,11 @@
+#objdump: -dr --prefix-addresses
+#as: -32
+#name: MIPS R5900 load $zero
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lq	zero,22136\(at\)
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-q.s
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-q.s	2013-05-28 17:20:02.933802181 +0100
@@ -0,0 +1,7 @@
+	.text
+foo:
+	lq	$0, 0x12345678($2)
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-u.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-u.d	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,15 @@
+#objdump: -dr --prefix-addresses
+#as: -32
+#name: microMIPS load $zero
+
+.*: +file format .*mips.*
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> ori	at,at,0x5000
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lwp	zero,1656\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> ori	at,at,0x5000
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> ldp	zero,1656\(at\)
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-u.s
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero-u.s	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,8 @@
+	.text
+foo:
+	lwp	$0, 0x12345678($2)
+	ldp	$0, 0x12345678($2)
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero.d	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,23 @@
+#objdump: -dr --prefix-addresses
+#as: -32
+#name: MIPS load $zero
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lb	zero,22136\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lbu	zero,22136\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lh	zero,22136\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lhu	zero,22136\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lw	zero,22136\(at\)
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero.s
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/ld-zero.s	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,11 @@
+	.text
+foo:
+	lb	$0, 0x12345678($2)
+	lbu	$0, 0x12345678($2)
+	lh	$0, 0x12345678($2)
+	lhu	$0, 0x12345678($2)
+	lw	$0, 0x12345678($2)
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/micromips@ld-zero-2.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/micromips@ld-zero-2.d	2013-05-28 17:04:54.312748324 +0100
@@ -0,0 +1,13 @@
+#objdump: -dr --prefix-addresses
+#as: -32
+#name: MIPS II load $zero
+#source: ld-zero-2.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> ori	at,at,0x5000
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> ll	zero,1656\(at\)
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/micromips@ld-zero-3.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/micromips@ld-zero-3.d	2013-05-28 17:04:54.813831749 +0100
@@ -0,0 +1,21 @@
+#objdump: -dr --prefix-addresses
+#as: -32
+#name: MIPS III load $zero
+#source: ld-zero-3.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> ori	at,at,0x5000
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lwu	zero,1656\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> addu	at,v0,at
+[0-9a-f]+ <[^>]*> lw	zero,22136\(at\)
+[0-9a-f]+ <[^>]*> lw	at,22140\(at\)
+[0-9a-f]+ <[^>]*> lui	at,0x1234
+[0-9a-f]+ <[^>]*> ori	at,at,0x5000
+[0-9a-f]+ <[^>]*> addu	at,at,v0
+[0-9a-f]+ <[^>]*> lld	zero,1656\(at\)
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/mips.exp
===================================================================
--- binutils-fsf-trunk-quilt.orig/gas/testsuite/gas/mips/mips.exp	2013-05-26 13:50:08.000000000 +0100
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/mips.exp	2013-05-28 17:33:08.033833129 +0100
@@ -698,6 +698,11 @@ if { [istarget mips*-*-vxworks*] } {
 					[mips_arch_list_matching mips3 !singlefloat]
 	}
     }
+    run_dump_test_arches "ld-zero"	[mips_arch_list_matching mips1]
+    run_dump_test_arches "ld-zero-2"	[mips_arch_list_matching mips2 !nollsc]
+    run_dump_test_arches "ld-zero-3"	[mips_arch_list_matching mips3 !nollsc]
+    run_dump_test_arches "ld-zero-u"	[mips_arch_list_matching micromips]
+    run_dump_test_arches "ld-zero-q"	[mips_arch_list_matching r5900]
     if $elf { run_dump_test "ld-svr4pic" }
     if $elf { run_dump_test "ld-xgot" }
     run_dump_test_arches "li"		[mips_arch_list_matching mips1]
Follow-Ups:
- Re: [PATCH] MIPS/GAS: Don't use $zero for address calculation
  - From: Richard Sandiford
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