From 6fd140757c318380907c82ef4c925519c7051332 Mon Sep 17 00:00:00 2001 From: Geoffrey Keating Date: Wed, 31 Jul 2002 00:11:31 +0000 Subject: [PATCH] extend.texi (Hints implementation): Document that GCC mostly ignores `register'. * doc/extend.texi (Hints implementation): Document that GCC mostly ignores `register'. From-SVN: r55890 --- gcc/ChangeLog | 5 +++++ gcc/doc/extend.texi | 21 +++++++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 01fd54a1674..311566bd49a 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2002-07-30 Geoffrey Keating + + * doc/extend.texi (Hints implementation): Document that GCC + mostly ignores `register'. + 2002-07-30 Toon Moene * flags.h: Declare flag_finite_math_only. diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 6fdf7ffcbfd..0ddcb345161 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -248,6 +248,27 @@ of the same array (6.5.6).} @cite{The extent to which suggestions made by using the @code{register} storage-class specifier are effective (6.7.1).} +The @code{register} specifier affects code generation only in these ways: + +@itemize @bullet +@item +When used as part of the register variable extension, see +@ref{Explicit Reg Vars}. + +@item +When @option{-O0} is in use, the compiler allocates distinct stack +memory for all variables that do not have the @code{register} +storage-class specifier; if @code{register} is specified, the variable +may have a shorter lifespan than the code would indicate and may never +be placed in memory. + +@item +On some rare x86 targets, @code{setjmp} doesn't save the registers in +all circumstances. In those cases, GCC doesn't allocate any variables +in registers unless they are marked @code{register}. + +@end itemize + @item @cite{The extent to which suggestions made by using the inline function specifier are effective (6.7.4).}