* doc/md.texi (msub@var{m}@var{n}4, usub@var{m}@var{n}4): Document.

* optabs.h (OTI_smsub_widen, OTI_umsub_widen): New optab_indexes.
(smsub_widen_optab, umsub_widen_optab): Define.
* optabs.c (init_optabs): Initialize smsub_widen_optab and
umsub_widen_optab.
* genopinit.c (optabs): Fill in smsub_widen_optab and
umsub_widen_optab.
* expr.c (expand_expr_real_1): Try to use smsub_widen_optab
and umsub_widen_optab to implement multiply-subtract sequences.
* config/mips/mips.md (*msac<u>_di): Rename to...
(<u>msubsidi4): ...this.  Extend condition to include
GENERATE_MADD_MSUB and TARGET_DSPR2.  Change the constraint
of operand 0 to "ka" and use the three-operand form of msub<u>
for TARGET_DSPR2.
* config/mips/mips-dspr2.md (mips_msub, mips_msubu): Convert
to define_expands.


git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@124558 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 19 insertions, 0 deletions

diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 56cc60f2e1e..53c5769f788 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -3687,6 +3687,25 @@ These instructions are not allowed to @code{FAIL}.
 Like @code{madd@var{m}@var{n}4}, but zero-extend the multiplication
 operands instead of sign-extending them.
 
+@cindex @code{msub@var{m}@var{n}4} instruction pattern
+@item @samp{msub@var{m}@var{n}4}
+Multiply operands 1 and 2, sign-extend them to mode @var{n}, subtract the
+result from operand 3, and store the result in operand 0.  Operands 1 and 2
+have mode @var{m} and operands 0 and 3 have mode @var{n}.
+Both modes must be integer modes and @var{n} must be twice
+the size of @var{m}.
+
+In other words, @code{msub@var{m}@var{n}4} is like
+@code{mul@var{m}@var{n}3} except that it also subtracts the result
+from operand 3.
+
+These instructions are not allowed to @code{FAIL}.
+
+@cindex @code{umsub@var{m}@var{n}4} instruction pattern
+@item @samp{umsub@var{m}@var{n}4}
+Like @code{msub@var{m}@var{n}4}, but zero-extend the multiplication
+operands instead of sign-extending them.
+
 @cindex @code{divmod@var{m}4} instruction pattern
 @item @samp{divmod@var{m}4}
 Signed division that produces both a quotient and a remainder.