Re: src/gas ChangeLog config/tc-mips.c

Re: src/gas ChangeLog config/tc-mips.c

[Ian Lance Taylor]

hjl@sourceware.cygnus.com writes:

> CVSROOT:	/cvs/src
> Module name:	src
> Changes by:	hjl@sources.redhat.com	2001-06-08 22:24:39
> 
> Modified files:
> 	gas            : ChangeLog 
> 	gas/config     : tc-mips.c 
> 
> Log message:
> 	2001-06-08  H.J. Lu  <hjl@gnu.org>
> 	
> 	* config/tc-mips.c (warn_nops): New variable. Set to 0 to
> 	disable warning about all NOPS that the assembler generates.
> 	(macro): Warn NOPS generated only if warn_nops is not 0.
> 	(md_shortopts): Add `n'.
> 	(md_parse_option): Set warn_nops to 1 for `n'.
> 
> Patches:
> http://sources.redhat.com/cgi-bin/cvsweb.cgi/src/gas/ChangeLog.diff?cvsroot=src&r1=1.895&r2=1.896
> http://sources.redhat.com/cgi-bin/cvsweb.cgi/src/gas/config/tc-mips.c.diff?cvsroot=src&r1=1.46&r2=1.47

This seems to add an option.  That must be documented in
gas/doc/c-mips.texi; how else will anybody know about it?  Did you
update md_show_usage?  It also seems to change behaviour.  That should
probably be documented in gas/NEWS.

Ian

Re: src/gas ChangeLog config/tc-mips.c

[H . J . Lu]

On Mon, Jun 11, 2001 at 08:29:26AM -0700, Ian Lance Taylor wrote:
> 
> This seems to add an option.  That must be documented in
> gas/doc/c-mips.texi; how else will anybody know about it?  Did you
> update md_show_usage?  It also seems to change behaviour.  That should
> probably be documented in gas/NEWS.
> 
> Ian

How about this?

BTW, does anyone know why we have to duplicate the machine specific
usage in both doc/as.texinfo and gas/doc/c-arch.texi? Shouldn't the
one in doc/as.texinfo be enough?

Thanks.


H.J.
----
2001-06-11  H.J. Lu  <hjl@gnu.org>

	* NEWS: Updated for the new -n option for the MIPS assembler.

	* config/tc-mips.c (md_show_usage): Add -n.

	* doc/as.texinfo: Document the new -n option.
	* doc/c-mips.texi: Likewise.
	* doc/as.1: Regnerated.

Index: NEWS
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/NEWS,v
retrieving revision 1.1.1.15
diff -u -p -r1.1.1.15 NEWS
--- NEWS	2001/01/23 18:59:58	1.1.1.15
+++ NEWS	2001/06/11 16:29:42
@@ -1,5 +1,9 @@
 -*- text -*-
 
+The MIPS assembler no longer issues a warning by default when it
+generates a nop instruction from a macro. The new command line option
+-n will turn on the warning.
+
 Changes in 2.11:
 
 x86 gas now supports the full Pentium4 instruction set.
Index: config/tc-mips.c
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/config/tc-mips.c,v
retrieving revision 1.41
diff -u -p -r1.41 tc-mips.c
--- config/tc-mips.c	2001/06/10 17:31:48	1.41
+++ config/tc-mips.c	2001/06/11 16:29:43
@@ -9331,6 +9331,7 @@ MIPS options:\n\
   fprintf (stream, _("\
 -O0			remove unneeded NOPs, do not swap branches\n\
 -O			remove unneeded NOPs and swap branches\n\
+-n			warn NOPs generated from macros\n\
 --[no-]construct-floats [dis]allow floating point values to be constructed\n\
 --trap, --no-break	trap exception on div by 0 and mult overflow\n\
 --break, --no-trap	break exception on div by 0 and mult overflow\n"));
Index: doc/as.1
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/doc/as.1,v
retrieving revision 1.1.1.8
diff -u -p -r1.1.1.8 as.1
--- doc/as.1	2001/04/24 16:13:08	1.1.1.8
+++ doc/as.1	2001/06/11 16:29:43
@@ -1,5 +1,5 @@
 .\" Automatically generated by Pod::Man version 1.02
-.\" Fri Apr 13 11:27:39 2001
+.\" Mon Jun 11 09:28:09 2001
 .\"
 .\" Standard preamble:
 .\" ======================================================================
@@ -137,7 +137,7 @@
 .\" ======================================================================
 .\"
 .IX Title "AS 1"
-.TH AS 1 "binutils-2.11.90" "2001-04-13" "GNU"
+.TH AS 1 "binutils-2.11.90" "2001-06-11" "GNU"
 .UC
 .SH "NAME"
 \&\s-1AS\s0 \- the portable \s-1GNU\s0 assembler.
@@ -192,7 +192,7 @@ as [ \-a[cdhlns][=file] ] [ \-D ]  [ \-\
  [ \-mips1 ] [ \-mips2 ] [ \-mips3 ] [ \-mips4 ] [ \-mips5 ]
  [ \-mips32 ] [ \-mips64 ]
  [ \-m4650 ] [ \-no-m4650 ]
- [ \-\-trap ] [ \-\-break ]
+ [ \-\-trap ] [ \-\-break ] [ \-n ]
  [ \-\-emulation=\fIname\fR ]
  [ \*(-- | \fIfiles\fR ... ]
 .SH "DESCRIPTION"
@@ -677,6 +677,10 @@ Control how to deal with multiplication 
 (and only work for Instruction Set Architecture level 2 and higher);
 \&\fB\*(--break\fR or \fB\*(--no-trap\fR (also synonyms, and the default) take a
 break exception.
+.Ip "\f(CW\*(C`\-n\*(C'\fR" 4
+.IX Item "-n"
+When this option is used, \f(CW\*(C`as\*(C'\fR will issue a warning every
+time it generates a nop instruction from a macro.
 .PP
 The following options are available when as is configured for
 an MCore processor.
Index: doc/as.texinfo
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/doc/as.texinfo,v
retrieving revision 1.24
diff -u -p -r1.24 as.texinfo
--- doc/as.texinfo	2001/03/27 16:55:14	1.24
+++ doc/as.texinfo	2001/06/11 16:29:43
@@ -332,7 +332,7 @@ gcc(1), ld(1), and the Info entries for 
  [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -mips4 ] [ -mips5 ]
  [ -mips32 ] [ -mips64 ]
  [ -m4650 ] [ -no-m4650 ]
- [ --trap ] [ --break ]
+ [ --trap ] [ --break ] [ -n ]
  [ --emulation=@var{name} ]
 @end ifset
  [ -- | @var{files} @dots{} ]
@@ -829,6 +829,10 @@ Control how to deal with multiplication 
 (and only work for Instruction Set Architecture level 2 and higher);
 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
 break exception.
+
+@item -n
+When this option is used, @code{@value{AS}} will issue a warning every
+time it generates a nop instruction from a macro.
 @end table
 @end ifset
 
Index: doc/c-mips.texi
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/doc/c-mips.texi,v
retrieving revision 1.1.1.9
diff -u -p -r1.1.1.9 c-mips.texi
--- doc/c-mips.texi	2001/03/09 19:17:15	1.1.1.9
+++ doc/c-mips.texi	2001/06/11 16:29:43
@@ -189,6 +189,10 @@ are only supported at Instruction Set Ar
 @itemx --no-trap
 Generate code to take a break exception rather than a trap exception when an
 error is detected.  This is the default.
+
+@item -n
+When this option is used, @code{@value{AS}} will issue a warning every
+time it generates a nop instruction from a macro.
 @end table
 
 @node MIPS Object

Re: src/gas ChangeLog config/tc-mips.c

[Philip Blundell]

>>+-n			warn NOPs generated from macros\n\

I think you have missed a word out there.  You also mistyped `Regenerated' in 
your changelog entry.

p.


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Re: src/gas ChangeLog config/tc-mips.c

[H . J . Lu]

On Mon, Jun 11, 2001 at 06:23:13PM +0100, Philip Blundell wrote:
> >>+-n			warn NOPs generated from macros\n\
> 
> I think you have missed a word out there.  You also mistyped `Regenerated' in 

What word is missing?

> your changelog entry.
> 

Fixed.  Thanks.


H.J.

Re: src/gas ChangeLog config/tc-mips.c

[Philip Blundell]

>> >>+-n			warn NOPs generated from macros\n\
>> 
>> I think you have missed a word out there.  You also mistyped `Regenerated' i
>n 
>
>What word is missing?

Well, the sentence doesn't make much sense as it stands.  I think you want 
"warn when NOPs are generated from macros" or "warn about NOPs generated from 
macros".

p.


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Re: src/gas ChangeLog config/tc-mips.c

[H . J . Lu]

On Mon, Jun 11, 2001 at 06:57:09PM +0100, Philip Blundell wrote:
> >> >>+-n			warn NOPs generated from macros\n\
> >> 
> >> I think you have missed a word out there.  You also mistyped `Regenerated' i
> >n 
> >
> >What word is missing?
> 
> Well, the sentence doesn't make much sense as it stands.  I think you want 
> "warn when NOPs are generated from macros" or "warn about NOPs generated from 
> macros".
> 

Thanks. Here is the new one. Any other objections?


H.J.
----
2001-06-11  H.J. Lu  <hjl@gnu.org>

	* NEWS: Updated for the new -n option for the MIPS assembler.

	* config/tc-mips.c (md_show_usage): Add -n.

	* doc/as.texinfo: Document the new -n option.
	* doc/c-mips.texi: Likewise.
	* doc/as.1: Regenerated.

Index: NEWS
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/NEWS,v
retrieving revision 1.1.1.15
diff -u -p -r1.1.1.15 NEWS
--- NEWS	2001/01/23 18:59:58	1.1.1.15
+++ NEWS	2001/06/11 16:31:55
@@ -1,5 +1,9 @@
 -*- text -*-
 
+The MIPS assembler no longer issues a warning by default when it
+generates a nop instruction from a macro. The new command line option
+-n will turn on the warning.
+
 Changes in 2.11:
 
 x86 gas now supports the full Pentium4 instruction set.
Index: config/tc-mips.c
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/config/tc-mips.c,v
retrieving revision 1.41
diff -u -p -r1.41 tc-mips.c
--- config/tc-mips.c	2001/06/10 17:31:48	1.41
+++ config/tc-mips.c	2001/06/11 17:59:41
@@ -9331,6 +9331,7 @@ MIPS options:\n\
   fprintf (stream, _("\
 -O0			remove unneeded NOPs, do not swap branches\n\
 -O			remove unneeded NOPs and swap branches\n\
+-n			warn about NOPs generated from macros\n\
 --[no-]construct-floats [dis]allow floating point values to be constructed\n\
 --trap, --no-break	trap exception on div by 0 and mult overflow\n\
 --break, --no-trap	break exception on div by 0 and mult overflow\n"));
Index: doc/as.1
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/doc/as.1,v
retrieving revision 1.1.1.8
diff -u -p -r1.1.1.8 as.1
--- doc/as.1	2001/04/24 16:13:08	1.1.1.8
+++ doc/as.1	2001/06/11 16:31:56
@@ -1,5 +1,5 @@
 .\" Automatically generated by Pod::Man version 1.02
-.\" Fri Apr 13 11:27:39 2001
+.\" Mon Jun 11 09:28:09 2001
 .\"
 .\" Standard preamble:
 .\" ======================================================================
@@ -137,7 +137,7 @@
 .\" ======================================================================
 .\"
 .IX Title "AS 1"
-.TH AS 1 "binutils-2.11.90" "2001-04-13" "GNU"
+.TH AS 1 "binutils-2.11.90" "2001-06-11" "GNU"
 .UC
 .SH "NAME"
 \&\s-1AS\s0 \- the portable \s-1GNU\s0 assembler.
@@ -192,7 +192,7 @@ as [ \-a[cdhlns][=file] ] [ \-D ]  [ \-\
  [ \-mips1 ] [ \-mips2 ] [ \-mips3 ] [ \-mips4 ] [ \-mips5 ]
  [ \-mips32 ] [ \-mips64 ]
  [ \-m4650 ] [ \-no-m4650 ]
- [ \-\-trap ] [ \-\-break ]
+ [ \-\-trap ] [ \-\-break ] [ \-n ]
  [ \-\-emulation=\fIname\fR ]
  [ \*(-- | \fIfiles\fR ... ]
 .SH "DESCRIPTION"
@@ -677,6 +677,10 @@ Control how to deal with multiplication 
 (and only work for Instruction Set Architecture level 2 and higher);
 \&\fB\*(--break\fR or \fB\*(--no-trap\fR (also synonyms, and the default) take a
 break exception.
+.Ip "\f(CW\*(C`\-n\*(C'\fR" 4
+.IX Item "-n"
+When this option is used, \f(CW\*(C`as\*(C'\fR will issue a warning every
+time it generates a nop instruction from a macro.
 .PP
 The following options are available when as is configured for
 an MCore processor.
Index: doc/as.texinfo
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/doc/as.texinfo,v
retrieving revision 1.24
diff -u -p -r1.24 as.texinfo
--- doc/as.texinfo	2001/03/27 16:55:14	1.24
+++ doc/as.texinfo	2001/06/11 16:31:56
@@ -332,7 +332,7 @@ gcc(1), ld(1), and the Info entries for 
  [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -mips4 ] [ -mips5 ]
  [ -mips32 ] [ -mips64 ]
  [ -m4650 ] [ -no-m4650 ]
- [ --trap ] [ --break ]
+ [ --trap ] [ --break ] [ -n ]
  [ --emulation=@var{name} ]
 @end ifset
  [ -- | @var{files} @dots{} ]
@@ -829,6 +829,10 @@ Control how to deal with multiplication 
 (and only work for Instruction Set Architecture level 2 and higher);
 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
 break exception.
+
+@item -n
+When this option is used, @code{@value{AS}} will issue a warning every
+time it generates a nop instruction from a macro.
 @end table
 @end ifset
 
Index: doc/c-mips.texi
===================================================================
RCS file: /work/cvs/gnu/binutils/gas/doc/c-mips.texi,v
retrieving revision 1.1.1.9
diff -u -p -r1.1.1.9 c-mips.texi
--- doc/c-mips.texi	2001/03/09 19:17:15	1.1.1.9
+++ doc/c-mips.texi	2001/06/11 16:31:56
@@ -189,6 +189,10 @@ are only supported at Instruction Set Ar
 @itemx --no-trap
 Generate code to take a break exception rather than a trap exception when an
 error is detected.  This is the default.
+
+@item -n
+When this option is used, @code{@value{AS}} will issue a warning every
+time it generates a nop instruction from a macro.
 @end table
 
 @node MIPS Object

Re: src/gas ChangeLog config/tc-mips.c

[Ian Lance Taylor]

"H . J . Lu" <hjl@lucon.org> writes:

> BTW, does anyone know why we have to duplicate the machine specific
> usage in both doc/as.texinfo and gas/doc/c-arch.texi? Shouldn't the
> one in doc/as.texinfo be enough?

Personally, I don't think the recitation of options in as.texinfo
helps much.  I tend to think the machine specific usage should be only
in c-ARCH.texi.  But I also think any rearrangement should only be
done by somebody willing to improve the manual organization as a
whole.

Ian

Is this correct ?

[Tat Kee Tan]

Hi,

I have this C code which is compiled using arm-linux-gcc 2.95.3
Using one ldr instruction should get to the value of prev_limit,
why does it take a sequence of two ldr instructions ? See below

static long all_requests;

long get_request(int n)
{
        static long prev_found = 0, prev_limit = 0;
        long req, limit;

        limit = all_requests + n;
        if (limit != prev_limit) {
                prev_limit = limit;
                prev_found = all_requests;
        }
        req = prev_found;

        return(req);
}

The compiled code is
.
.
long get_request(int n)
{
    80bc:       e50b0010        str     r0, [fp, -#16]
        static long prev_found = 0, prev_limit = 0;
        long req, limit;

        limit = all_requests + n;
    80c0:       e59f3054        ldr     r3, [pc, #54]   ; 811c
<get_request+0x70>
    80c4:       e5932000        ldr     r2, [r3]
    80c8:       e51b3010        ldr     r3, [fp, -#16]
    80cc:       e0822003        add     r2, r2, r3
    80d0:       e50b2018        str     r2, [fp, -#24]
        if (limit != prev_limit) {
    80d4:       e59f3044        ldr     r3, [pc, #44]   ; 8120
<get_request+0x74>
    80d8:       e51b2018        ldr     r2, [fp, -#24]
    80dc:       e5933000        ldr     r3, [r3]
    80e0:       e1520003        cmp     r2, r3
    80e4:       0a000006        beq     8104 <get_request+0x58>
                prev_limit = limit;
    80e8:       e59f3030        ldr     r3, [pc, #30]   ; 8120
<get_request+0x74>

Re: Is this correct ?

[Nick Clifton]

Hi Tat Kee Tan,

> I have this C code which is compiled using arm-linux-gcc 2.95.3

First of all, this question should have been posted to the gcc-help
mailing list (gcc-help@gcc.gnu.org), not the binutils list, since it
is about code geenration by the compiler.

> Using one ldr instruction should get to the value of prev_limit,
> why does it take a sequence of two ldr instructions ? See below

>     80d4:       e59f3044        ldr     r3, [pc, #44]   ; 8120
>     80dc:       e5933000        ldr     r3, [r3]

The reason is that 'prev_limit' is a static variable, not a local
variable.  Therefore it will be stored in the .data section and not on
the stack.  Since the compiler does not know where the .data section
will be located in memory it cannot just use a pc-relative load to get
the value.  Instead the address of 'prev_limit' has to be stored in a
word at the end of the get_request() function, and then two LDRs are
used to load the value.  The first LDR loads the address of
'prev_limit' from the word at the end of the function.  The second LDR
loads the contents of this address into R3.

Cheers
        Nick

Re: Is this correct ?

[Richard Earnshaw]

> > Using one ldr instruction should get to the value of prev_limit,
> > why does it take a sequence of two ldr instructions ? See below
> 
> >     80d4:       e59f3044        ldr     r3, [pc, #44]   ; 8120
> >     80dc:       e5933000        ldr     r3, [r3]
> 
> The reason is that 'prev_limit' is a static variable, not a local
> variable.  Therefore it will be stored in the .data section and not on
> the stack.  Since the compiler does not know where the .data section
> will be located in memory it cannot just use a pc-relative load to get
> the value.

Nearly, but not quite.

On the ARM, the pc-relative load is limited to a range of +/- 4Kbytes from 
the current address.  Since we cannot guarantee that the local variable 
will be in that range (in fact we can virtually guarantee that it won't -- 
most of that range will be code not data) we must use a pc-relative load 
to get the address of the variable and then load its value using that.

>  Instead the address of 'prev_limit' has to be stored in a
> word at the end of the get_request() function, and then two LDRs are
> used to load the value.  The first LDR loads the address of
> 'prev_limit' from the word at the end of the function.  The second LDR
> loads the contents of this address into R3.

R.