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| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/doc/invoke.texi | 8 |
2 files changed, 8 insertions, 5 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f5ec63a..ea6a6bb 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2006-09-12 H.J. Lu <hongjiu.lu@intel.com> + + * doc/invoke.texi (mpreferred-stack-boundary): Remove exception + for -Os. Update __m128 alignment requirement. + 2006-09-13 Jan Hubicka <jh@suse.cz> * cfganal.c (compute_dominance_frontiers_1): Don't be quadratic. diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index d7f0826..38d227f 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -9505,15 +9505,13 @@ applicable to individual functions. @opindex mpreferred-stack-boundary Attempt to keep the stack boundary aligned to a 2 raised to @var{num} byte boundary. If @option{-mpreferred-stack-boundary} is not specified, -the default is 4 (16 bytes or 128 bits), except when optimizing for code -size (@option{-Os}), in which case the default is the minimum correct -alignment (4 bytes for x86, and 8 bytes for x86-64). +the default is 4 (16 bytes or 128 bits). On Pentium and PentiumPro, @code{double} and @code{long double} values should be aligned to an 8 byte boundary (see @option{-malign-double}) or suffer significant run time performance penalties. On Pentium III, the -Streaming SIMD Extension (SSE) data type @code{__m128} suffers similar -penalties if it is not 16 byte aligned. +Streaming SIMD Extension (SSE) data type @code{__m128} may not work +properly if it is not 16 byte aligned. To ensure proper alignment of this values on the stack, the stack boundary must be as aligned as that required by any value stored on the stack. |