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| author | Geoffrey Keating <geoffk@greed.local> | 2003-12-30 20:27:53 +0000 |
|---|---|---|
| committer | Geoffrey Keating <geoffk@gcc.gnu.org> | 2003-12-30 20:27:53 +0000 |
| commit | 222a2f1afb8130c98cbf42edb982e87f221fe4ff (patch) | |
| tree | 910d863649df21fad7a3b3035c97ecc3b25d907b /gcc | |
| parent | cca9b4b54d86897efe9f691274a2a9fbd0c15b5e (diff) | |
| download | gcc-222a2f1afb8130c98cbf42edb982e87f221fe4ff.zip gcc-222a2f1afb8130c98cbf42edb982e87f221fe4ff.tar.gz gcc-222a2f1afb8130c98cbf42edb982e87f221fe4ff.tar.bz2 | |
tm.texi (PREFERRED_RELOAD_CLASS): Describe use of NO_REGS with constants.
* doc/tm.texi (PREFERRED_RELOAD_CLASS): Describe use of NO_REGS
with constants.
From-SVN: r75245
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/doc/tm.texi | 15 |
2 files changed, 16 insertions, 4 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index b84f4cf..4272091 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2003-12-30 Geoffrey Keating <geoffk@greed.local> + + * doc/tm.texi (PREFERRED_RELOAD_CLASS): Describe use of NO_REGS + with constants. + 2003-12-30 Mark Mitchell <mark@codesourcery.com> * stor-layout.c (layout_decl): Turn bitfields into ordinary diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi index 6b8ad5e..fa0e189 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -2419,10 +2419,17 @@ for a @samp{moveq} instruction, the value of this macro is always @code{DATA_REGS} as long as @var{class} includes the data registers. Requiring a data register guarantees that a @samp{moveq} will be used. -If @var{x} is a @code{const_double}, by returning @code{NO_REGS} -you can force @var{x} into a memory constant. This is useful on -certain machines where immediate floating values cannot be loaded into -certain kinds of registers. +One case where @code{PREFERRED_RELOAD_CLASS} must not return +@var{class} is if @var{x} is a legitimate constant which cannot be +loaded into some register class. By returning @code{NO_REGS} you can +force @var{x} into a memory location. For example, rs6000 can load +immediate values into general-purpose registers, but does not have an +instruction for loading an immediate value into a floating-point +register, so @code{PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when +@var{x} is a floating-point constant. If the constant can't be loaded +into any kind of register, code generation will be better if +@code{LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead +of using @code{PREFERRED_RELOAD_CLASS}. @end defmac @defmac PREFERRED_OUTPUT_RELOAD_CLASS (@var{x}, @var{class}) |