OpenE2K
/
gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

implement-c.texi (Integers Implementation): Make GCC's promises about signed left shift stronger and clarify the cases when... 

2015-11-26  Paolo Bonzini <bonzini@gnu.org>

	* doc/implement-c.texi (Integers Implementation): Make GCC's promises
	about signed left shift stronger and clarify the cases when they're
	broken.

From-SVN: r230931
This commit is contained in:
Paolo Bonzini 2015-11-26 10:16:56 +00:00
parent b3877860a8
commit a37a22da2d
2 changed files with 14 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
gcc/ChangeLog
View File

@ -1,3 +1,9 @@
2015-11-26 Paolo Bonzini <bonzini@gnu.org>
* doc/implement-c.texi (Integers Implementation): Make GCC's promises
about signed left shift stronger and clarify the cases when they're
broken.
2015-11-26 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Bernd Schmidt <bschmidt@redhat.com>
@ -7682,6 +7688,9 @@
* fold-const.c (fold_binary_loc) : Move (-A) * (-B) -> A * B
to match.pd.
* doc/implement-c.texi (Integers Implementation): Make GCC's promises
about signed left shift stronger and clarify the cases when they're
broken.
Move (a * (1 << b)) is (a << b) to match.pd.
Move convert (C1/X)*C2 into (C1*C2)/X to match.pd.
Move ~X & X, (X == 0) & X, and !X & X are zero to match.pd.

8
gcc/doc/implement-c.texi
View File

@ -266,9 +266,11 @@ both the sign and value bits, where the sign bit is considered
immediately above the highest-value value bit. Signed @samp{>>} acts
on negative numbers by sign extension.
GCC does not use the latitude given in C99 and C11 only to treat certain
aspects of signed @samp{<<} as undefined, but this is subject to
change.
As an extension to the C language, GCC does not use the latitude given in
C99 and C11 only to treat certain aspects of signed @samp{<<} as undefined.
However, @option{-fsanitize=shift} (and @option{-fsanitize=undefined}) will
diagnose such cases. They are also diagnosed where constant
expressions are required.
@item
@cite{The sign of the remainder on integer division (C90 6.3.5).}