gas: detect DCTI couples in sparc

Before SPARC V9 the effect of having a delayed branch instruction in the
delay slot of a conditional delayed branch was undefined.

In SPARC V9 DCTI couples are well defined.

However, starting with the UltraSPARC Architecture 2005, DCTI
couples (of all kind) are deprecated and should not be used, as they may
be slow or behave differently to what the programmer expects.

This patch adds a new command line option --dcti-couples-detect to `as',
disabled by default, that makes the assembler to warn the user if an
unpredictable DCTI couple is found.  Tests and documentation are
included.

gas/ChangeLog:

2016-09-14  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* config/tc-sparc.c (md_assemble): Detect and warning on
	unpredictable DCTI couples in certain arches.
	(dcti_couples_detect): New global.
	(md_longopts): Add command line option -dcti-couples-detect.
	(md_show_usage): Document -dcti-couples-detect.
	(md_parse_option): Handle OPTION_DCTI_COUPLES_DETECT.
	* testsuite/gas/sparc/sparc.exp (gas_64_check): Run
	dcti-couples-v8, dcti-couples-v9 and dcti-couples-v9c tests.
	* testsuite/gas/sparc/dcti-couples.s: New file.
	* testsuite/gas/sparc/dcti-couples-v9c.d: Likewise.
	* testsuite/gas/sparc/dcti-couples-v8.d: Likewise.
	* testsuite/gas/sparc/dcti-couples-v9.d: Likewise.
	* testsuite/gas/sparc/dcti-couples-v9c.l: Likewise.
	* testsuite/gas/sparc/dcti-couples-v8.l: Likewise.
	* doc/as.texinfo (Overview): Document --dcti-couples-detect.
	* doc/c-sparc.texi (Sparc-Opts): Likewise.

1 files changed, 10 insertions, 4 deletions

diff --git a/gas/doc/c-sparc.texi b/gas/doc/c-sparc.texi
index e879276..1368f7d 100644
--- a/gas/doc/c-sparc.texi
+++ b/gas/doc/c-sparc.texi
@@ -71,10 +71,10 @@ is explicitly requested.  SPARC v9 is always incompatible with sparclite.
 @kindex -Asparcvis3
 @kindex -Asparcvis3r
 @item -Av6 | -Av7 | -Av8 | -Aleon | -Asparclet | -Asparclite
-@itemx -Av8plus | -Av8plusa | -Av8plusb | -Av8plusc | -Av8plusd | -Av8plusv
+@itemx -Av8plus | -Av8plusa | -Av8plusb | -Av8plusc | -Av8plusd | -Av8plusv | -Av8plusm
 @itemx -Av9 | -Av9a | -Av9b | -Av9c | -Av9d | -Av9e | -Av9v | -Av9m
 @itemx -Asparc | -Asparcvis | -Asparcvis2 | -Asparcfmaf | -Asparcima
-@itemx -Asparcvis3 | -Asparcvis3r
+@itemx -Asparcvis3 | -Asparcvis3r | -Asparc5
 Use one of the @samp{-A} options to select one of the SPARC
 architectures explicitly.  If you select an architecture explicitly,
 @code{@value{AS}} reports a fatal error if it encounters an instruction
@@ -137,14 +137,14 @@ and floating point unfused multiply-add instructions enabled.
 @samp{-Asparc5} is equivalent to @samp{-Av9m}.
 
 @item -xarch=v8plus | -xarch=v8plusa | -xarch=v8plusb | -xarch=v8plusc
-@itemx -xarch=v8plusd | -xarch=v8plusv | -xarch=v9 | -xarch=v9a
+@itemx -xarch=v8plusd | -xarch=v8plusv | -xarch=v8plusm | -xarch=v9 | -xarch=v9a
 @itemx -xarch=v9b | -xarch=v9c | -xarch=v9d | -xarch=v9e | -xarch=v9v | -xarch=v9m
 @itemx -xarch=sparc | -xarch=sparcvis | -xarch=sparcvis2
 @itemx -xarch=sparcfmaf | -xarch=sparcima | -xarch=sparcvis3
 @itemx -xarch=sparcvis3r | -xarch=sparc5
 For compatibility with the SunOS v9 assembler.  These options are
 equivalent to -Av8plus, -Av8plusa, -Av8plusb, -Av8plusc, -Av8plusd,
--Av8plusv, -Av9, -Av9a, -Av9b, -Av9c, -Av9d, -Av9e, -Av9v, -Av9m,
+-Av8plusv, -Av8plusm, -Av9, -Av9a, -Av9b, -Av9c, -Av9d, -Av9e, -Av9v, -Av9m,
 -Asparc, -Asparcvis, -Asparcvis2, -Asparcfmaf, -Asparcima,
 -Asparcvis3, and -Asparcvis3r, respectively.
 
@@ -158,6 +158,12 @@ as required (except between incompatible levels).
 Select the word size, either 32 bits or 64 bits.
 These options are only available with the ELF object file format,
 and require that the necessary BFD support has been included.
+
+@item --dcti-couples-detect
+Warn if a DCTI (delayed control transfer instruction) couple is found
+when generating code for a variant of the SPARC architecture in which
+the execution of the couple is unpredictable, or very slow.  This is
+disabled by default.
 @end table
 
 @node Sparc-Aligned-Data