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cris: Don't default to -mmul-bug-workaround

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This flips the default for the errata handling for an old version
(TL;DR: workaround: no multiply instruction last on a cache-line).
Newer versions of the CRIS cpu don't have that bug.  While the impact
of the workaround is very marginal (coremark: less than .05% larger,
less than .0005% slower) it's an irritating pseudorandom factor when
assessing the impact of other changes.

Also, fix a wart requiring changes to more than TARGET_DEFAULT to flip
the default.

People building old kernels or operating systems to run on
ETRAX 100 LX are advised to pass "-mmul-bug-workaround".

gcc:
	* config/cris/cris.h (TARGET_DEFAULT): Don't include MASK_MUL_BUG.
	(MUL_BUG_ASM_DEFAULT): New macro.
	(MAYBE_AS_NO_MUL_BUG_ABORT): Define in terms of MUL_BUG_ASM_DEFAULT.
	* doc/invoke.texi (CRIS Options, -mmul-bug-workaround): Adjust
	accordingly.
This commit is contained in:
Hans-Peter Nilsson 2022-02-02 00:00:09 +01:00
parent ae7e4af964
commit 4c4d0af4c9
2 changed files with 17 additions and 4 deletions
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19
gcc/config/cris/cris.h
View File

@ -153,7 +153,9 @@ extern int cris_cpu_version;
#ifdef HAVE_AS_NO_MUL_BUG_ABORT_OPTION
#define MAYBE_AS_NO_MUL_BUG_ABORT \
"%{mno-mul-bug-workaround:-no-mul-bug-abort} "
"%{mno-mul-bug-workaround:-no-mul-bug-abort} " \
"%{mmul-bug-workaround:-mul-bug-abort} " \
"%{!mmul-bug-workaround:%{!mno-mul-bug-workaround:" MUL_BUG_ASM_DEFAULT "}} "
#else
#define MAYBE_AS_NO_MUL_BUG_ABORT
#endif
@ -255,15 +257,26 @@ extern int cris_cpu_version;
(MASK_SIDE_EFFECT_PREFIXES + MASK_STACK_ALIGN \
+ MASK_CONST_ALIGN + MASK_DATA_ALIGN \
+ MASK_ALIGN_BY_32 \
+ MASK_PROLOGUE_EPILOGUE + MASK_MUL_BUG)
+ MASK_PROLOGUE_EPILOGUE)
# else /* 0 */
# define TARGET_DEFAULT \
(MASK_SIDE_EFFECT_PREFIXES + MASK_STACK_ALIGN \
+ MASK_CONST_ALIGN + MASK_DATA_ALIGN \
+ MASK_PROLOGUE_EPILOGUE + MASK_MUL_BUG)
+ MASK_PROLOGUE_EPILOGUE)
# endif
#endif
/* Don't depend on the assembler default setting for the errata machinery;
always pass the option to turn it on or off explicitly. But, we have to
decide on which is the *GCC* default, and for that we should only need to
consider what's in TARGET_DEFAULT; no other changes should be necessary. */
#if (TARGET_DEFAULT & MASK_MUL_BUG)
#define MUL_BUG_ASM_DEFAULT "-mul-bug-abort"
#else
#define MUL_BUG_ASM_DEFAULT "-no-mul-bug-abort"
#endif
/* Local, providing a default for cris_cpu_version. */
#define CRIS_DEFAULT_CPU_VERSION TARGET_CPU_DEFAULT

2
gcc/doc/invoke.texi
View File

@ -22268,7 +22268,7 @@ The options @option{-metrax4} and @option{-metrax100} are synonyms for
@opindex mmul-bug-workaround
@opindex mno-mul-bug-workaround
Work around a bug in the @code{muls} and @code{mulu} instructions for CPU
models where it applies. This option is active by default.
models where it applies. This option is disabled by default.
@item -mpdebug
@opindex mpdebug