Add command line option to stop the assembler from padding the end of sections to their alignment boundary.
PR gas/20247
* as.h (do_not_pad_sections_to_alignment): New global variable.
* as.c (show_usage): Add --no-pad-sections.
(parse_args): Likewise.
* write.c (size_seg): Skip padding the end of the section if
requested from the command line.
(SUB_SEGMENT_ALIGN): Likewise.
* doc/as.texinfo: Document the new option.
* NEWS: Mention the new feature.
* testsuite/gas/elf/section11.s: New test.
* testsuite/gas/elf/section11.d: New test driver.
* testsuite/gas/elf/elf.exp: Run the new test.
diff --git a/gas/NEWS b/gas/NEWS
index a099060..08807f1 100644
--- a/gas/NEWS
+++ b/gas/NEWS
@@ -1,4 +1,7 @@
-*- text -*-
+* Add --no-pad-sections to stop the assembler from padding the end of output
+ sections up to their alignment boundary.
+
* Support for the ARMv8-M architecture has been added to the ARM port. Support
for the ARMv8-M Security and DSP Extensions has also been added to the ARM
port.
diff --git a/gas/as.c b/gas/as.c
index badeac9..8784fb4 100644
--- a/gas/as.c
+++ b/gas/as.c
@@ -342,6 +342,8 @@
fprintf (stream, _("\
-nocpp ignored\n"));
fprintf (stream, _("\
+ -no-pad-sections do not pad the end of sections to alignment boundaries\n"));
+ fprintf (stream, _("\
-o OBJFILE name the object-file output OBJFILE (default a.out)\n"));
fprintf (stream, _("\
-R fold data section into text section\n"));
@@ -479,7 +481,8 @@
OPTION_REDUCE_MEMORY_OVERHEADS,
OPTION_WARN_FATAL,
OPTION_COMPRESS_DEBUG,
- OPTION_NOCOMPRESS_DEBUG
+ OPTION_NOCOMPRESS_DEBUG,
+ OPTION_NO_PAD_SECTIONS /* = STD_BASE + 40 */
/* When you add options here, check that they do
not collide with OPTION_MD_BASE. See as.h. */
};
@@ -542,6 +545,7 @@
,{"MD", required_argument, NULL, OPTION_DEPFILE}
,{"mri", no_argument, NULL, 'M'}
,{"nocpp", no_argument, NULL, OPTION_NOCPP}
+ ,{"no-pad-sections", no_argument, NULL, OPTION_NO_PAD_SECTIONS}
,{"no-warn", no_argument, NULL, 'W'}
,{"reduce-memory-overheads", no_argument, NULL, OPTION_REDUCE_MEMORY_OVERHEADS}
,{"statistics", no_argument, NULL, OPTION_STATISTICS}
@@ -637,6 +641,10 @@
case OPTION_NOCPP:
break;
+ case OPTION_NO_PAD_SECTIONS:
+ do_not_pad_sections_to_alignment = 1;
+ break;
+
case OPTION_STATISTICS:
flag_print_statistics = 1;
break;
diff --git a/gas/as.h b/gas/as.h
index 51e16f1..169c714 100644
--- a/gas/as.h
+++ b/gas/as.h
@@ -76,8 +76,8 @@
150 isn't special; it's just an arbitrary non-ASCII char value. */
#define OPTION_STD_BASE 150
/* The first getopt value for machine-dependent long options.
- 190 gives the standard options room to grow. */
-#define OPTION_MD_BASE 190
+ 290 gives the standard options room to grow. */
+#define OPTION_MD_BASE 290
#ifdef DEBUG
#undef NDEBUG
@@ -377,6 +377,8 @@
leave lots of padding. */
COMMON int linkrelax;
+COMMON int do_not_pad_sections_to_alignment;
+
/* TRUE if we should produce a listing. */
extern int listing;
diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo
index 6d2c325..9ebfda0 100644
--- a/gas/doc/as.texinfo
+++ b/gas/doc/as.texinfo
@@ -235,6 +235,7 @@
[@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
[@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
[@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
+ [@b{--no-pad-sections}]
[@b{-o} @var{objfile}] [@b{-R}]
[@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
[@b{--statistics}]
@@ -773,6 +774,11 @@
Set the maximum number of lines printed in a listing for a single line of input
to @var{number} + 1.
+@item --no-pad-sections
+Stop the assembler for padding the ends of output sections to the alignment
+of that section. The default is to pad the sections, but this can waste space
+which might be needed on targets which have tight memory constraints.
+
@item -o @var{objfile}
Name the object-file output from @command{@value{AS}} @var{objfile}.
@@ -2158,6 +2164,7 @@
* listing:: --listing-XXX to configure listing output
* M:: -M or --mri to assemble in MRI compatibility mode
* MD:: --MD for dependency tracking
+* no-pad-sections:: --no-pad-sections to stop section padding
* o:: -o to name the object file
* R:: -R to join data and text sections
* statistics:: --statistics to see statistics about assembly
@@ -2494,6 +2501,15 @@
This feature is used in the automatic updating of makefiles.
+@node no-pad-sections
+@section Output Section Padding
+@kindex --no-pad-sections
+@cindex output section padding
+Normally the assembler will pad the end of each output section up to its
+alignment boundary. But this can waste space, which can be significant on
+memory constrained targets. So the @option{--no-pad-sections} option will
+disable this behaviour.
+
@node o
@section Name the Object File: @option{-o}
@@ -2680,7 +2696,7 @@
(@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
to get other ``CPP'' style preprocessing by giving the input file a
@samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
-Output, gcc.info, Using GNU CC} .
+Output, gcc info, Using GNU CC}.
Excess whitespace, comments, and character constants
cannot be used in the portions of the input text that are not
diff --git a/gas/testsuite/gas/elf/elf.exp b/gas/testsuite/gas/elf/elf.exp
index 95c9204..3e85ae2 100644
--- a/gas/testsuite/gas/elf/elf.exp
+++ b/gas/testsuite/gas/elf/elf.exp
@@ -205,6 +205,7 @@
run_dump_test "section8"
run_dump_test "section9"
run_dump_test "section10"
+ run_dump_test "section11"
run_dump_test "dwarf2-1"
run_dump_test "dwarf2-2"
run_dump_test "dwarf2-3"
diff --git a/gas/testsuite/gas/elf/section11.d b/gas/testsuite/gas/elf/section11.d
new file mode 100644
index 0000000..c1043db
--- /dev/null
+++ b/gas/testsuite/gas/elf/section11.d
@@ -0,0 +1,13 @@
+#as: --no-pad-sections
+#readelf: -S --wide
+#name: Disabling section padding
+# The RX port uses non standard section names.
+#skip: rx-*-*
+
+#...
+ \[ .\] .text[ ]+PROGBITS[ ]+0+00 0+[0-9a-f]+ 0+0(1|4|5) 00 AX 0 0 16
+#...
+ \[ .\] .data[ ]+PROGBITS[ ]+0+00 0+[0-9a-f]+ 0+01 00 WA 0 0 16
+#...
+ \[ .\] .bss[ ]+NOBITS[ ]+0+00 0+[0-9a-f]+ 0+01 00 WA 0 0 16
+#pass
diff --git a/gas/testsuite/gas/elf/section11.s b/gas/testsuite/gas/elf/section11.s
new file mode 100644
index 0000000..200d34c
--- /dev/null
+++ b/gas/testsuite/gas/elf/section11.s
@@ -0,0 +1,14 @@
+.section .bss
+.balign 16
+.skip 1
+
+
+.data
+.balign 16
+.skip 1
+
+
+.text
+.balign 16
+.skip 1
+
diff --git a/gas/write.c b/gas/write.c
index 0dfca0c..9af1f80 100644
--- a/gas/write.c
+++ b/gas/write.c
@@ -579,7 +579,12 @@
x = bfd_set_section_flags (abfd, sec, flags);
gas_assert (x);
- newsize = md_section_align (sec, size);
+ /* If permitted, allow the backend to pad out the section
+ to some alignment boundary. */
+ if (do_not_pad_sections_to_alignment)
+ newsize = size;
+ else
+ newsize = md_section_align (sec, size);
x = bfd_set_section_size (abfd, sec, newsize);
gas_assert (x);
@@ -1696,7 +1701,7 @@
}
/* Finish the subsegments. After every sub-segment, we fake an
- ".align ...". This conforms to BSD4.2 brane-damage. We then fake
+ ".align ...". This conforms to BSD4.2 brain-damage. We then fake
".fill 0" because that is the kind of frag that requires least
thought. ".align" frags like to have a following frag since that
makes calculating their intended length trivial. */
@@ -1708,6 +1713,7 @@
code-bearing sections. */
#define SUB_SEGMENT_ALIGN(SEG, FRCHAIN) \
(!(FRCHAIN)->frch_next && subseg_text_p (SEG) \
+ && !do_not_pad_sections_to_alignment \
? get_recorded_alignment (SEG) \
: 0)
#else
