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| author | Andrew Stubbs <ams@gcc.gnu.org> | 2011-06-07 10:58:16 +0000 |
|---|---|---|
| committer | Andrew Stubbs <ams@gcc.gnu.org> | 2011-06-07 10:58:16 +0000 |
| commit | c536876e065822e33b5c5019d93e527012dda160 (patch) | |
| tree | 976e83087ab821ec0d3bd318f9d66c071893b016 /gcc/doc | |
| parent | 308dc890dd4315560088e8e012d7ebddf0d887e7 (diff) | |
| download | gcc-c536876e065822e33b5c5019d93e527012dda160.zip gcc-c536876e065822e33b5c5019d93e527012dda160.tar.gz gcc-c536876e065822e33b5c5019d93e527012dda160.tar.bz2 | |
simplify-rtx.c (simplify_unary_operation_1): Canonicalize widening multiplies.
2011-06-07 Bernd Schmidt <bernds@codesourcery.com>
Andrew Stubbs <ams@codesourcery.com>
gcc/
* simplify-rtx.c (simplify_unary_operation_1): Canonicalize widening
multiplies.
* doc/md.texi (Canonicalization of Instructions): Document widening
multiply canonicalization.
gcc/testsuite/
* gcc.target/arm/mla-2.c: New test.
From-SVN: r174740
Diffstat (limited to 'gcc/doc')
| -rw-r--r-- | gcc/doc/md.texi | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi index 6fdcce5..0023405 100644 --- a/gcc/doc/md.texi +++ b/gcc/doc/md.texi @@ -5840,6 +5840,23 @@ Equality comparisons of a group of bits (usually a single bit) with zero will be written using @code{zero_extract} rather than the equivalent @code{and} or @code{sign_extract} operations. +@cindex @code{mult}, canonicalization of +@item +@code{(sign_extend:@var{m1} (mult:@var{m2} (sign_extend:@var{m2} @var{x}) +(sign_extend:@var{m2} @var{y})))} is converted to @code{(mult:@var{m1} +(sign_extend:@var{m1} @var{x}) (sign_extend:@var{m1} @var{y}))}, and likewise +for @code{zero_extend}. + +@item +@code{(sign_extend:@var{m1} (mult:@var{m2} (ashiftrt:@var{m2} +@var{x} @var{s}) (sign_extend:@var{m2} @var{y})))} is converted +to @code{(mult:@var{m1} (sign_extend:@var{m1} (ashiftrt:@var{m2} +@var{x} @var{s})) (sign_extend:@var{m1} @var{y}))}, and likewise for +patterns using @code{zero_extend} and @code{lshiftrt}. If the second +operand of @code{mult} is also a shift, then that is extended also. +This transformation is only applied when it can be proven that the +original operation had sufficient precision to prevent overflow. + @end itemize Further canonicalization rules are defined in the function |