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| author | Bernd Schmidt <crux@pool.informatik.rwth-aachen.de> | 1998-12-04 13:09:39 +0000 |
|---|---|---|
| committer | Bernd Schmidt <crux@gcc.gnu.org> | 1998-12-04 13:09:39 +0000 |
| commit | faa9eb19777eaf54cdc8c2bac01b9d4217e524bf (patch) | |
| tree | 70c98a19fbbf41025fff502c5bcd05dd63b55f6d | |
| parent | 4dab1f3e9f46e25c08a6f73cfe18ac81865917f4 (diff) | |
| download | gcc-faa9eb19777eaf54cdc8c2bac01b9d4217e524bf.zip gcc-faa9eb19777eaf54cdc8c2bac01b9d4217e524bf.tar.gz gcc-faa9eb19777eaf54cdc8c2bac01b9d4217e524bf.tar.bz2 | |
* tm.texi (SMALL_REGISTER_CLASSES): Make description match reality.
From-SVN: r24092
| -rw-r--r-- | gcc/ChangeLog | 2 | ||||
| -rw-r--r-- | gcc/tm.texi | 14 |
2 files changed, 8 insertions, 8 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index fac1096..d8bf206 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,7 @@ Fri Dec 4 20:15:57 1998 Bernd Schmidt <crux@pool.informatik.rwth-aachen.de> + * tm.texi (SMALL_REGISTER_CLASSES): Make description match reality. + * final.c (cleanup_subreg_operands): Delete some unused code. * recog.h (MAX_RECOG_ALTERNATIVES): New macro. diff --git a/gcc/tm.texi b/gcc/tm.texi index a33df5e..738ec16 100644 --- a/gcc/tm.texi +++ b/gcc/tm.texi @@ -2022,17 +2022,15 @@ is @code{BITS_PER_WORD} bits wide is correct for your machine. @findex SMALL_REGISTER_CLASSES @item SMALL_REGISTER_CLASSES -Normally the compiler avoids choosing registers that have been -explicitly mentioned in the rtl as spill registers (these registers are -normally those used to pass parameters and return values). However, -some machines have so few registers of certain classes that there -would not be enough registers to use as spill registers if this were -done. +On some machines, it is risky to let hard registers live across arbitrary +insns. Typically, these machines have instructions that require values +to be in specific registers (like an accumulator), and reload will fail +if the required hard register is used for another purpose across such an +insn. Define @code{SMALL_REGISTER_CLASSES} to be an expression with a non-zero value on these machines. When this macro has a non-zero value, the -compiler allows registers explicitly used in the rtl to be used as spill -registers but avoids extending the lifetime of these registers. +compiler will try to minimize the lifetime of hard registers. It is always safe to define this macro with a non-zero value, but if you unnecessarily define it, you will reduce the amount of optimizations |