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| author | Richard Sandiford <richard.sandiford@arm.com> | 2014-09-22 07:36:51 +0000 |
|---|---|---|
| committer | Richard Sandiford <rsandifo@gcc.gnu.org> | 2014-09-22 07:36:51 +0000 |
| commit | 0cb07998ae317e89dbf9695db731bfc8aa5f9d41 (patch) | |
| tree | e628812b6b8bd37be67d38a58cf45d98de1a1770 /gcc/rtlanal.c | |
| parent | 853d50d3c82212fee406279c386cef1673adfbc3 (diff) | |
| download | gcc-0cb07998ae317e89dbf9695db731bfc8aa5f9d41.zip gcc-0cb07998ae317e89dbf9695db731bfc8aa5f9d41.tar.gz gcc-0cb07998ae317e89dbf9695db731bfc8aa5f9d41.tar.bz2 | |
rtl.h (subreg_info): Expand commentary
gcc/
* rtl.h (subreg_info): Expand commentary
* rtlanal.c (subreg_get_info): Likewise.
From-SVN: r215447
Diffstat (limited to 'gcc/rtlanal.c')
| -rw-r--r-- | gcc/rtlanal.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c index e361f0f..3063458 100644 --- a/gcc/rtlanal.c +++ b/gcc/rtlanal.c @@ -3410,7 +3410,20 @@ subreg_lsb (const_rtx x) xmode - The mode of xregno. offset - The byte offset. ymode - The mode of a top level SUBREG (or what may become one). - info - Pointer to structure to fill in. */ + info - Pointer to structure to fill in. + + Rather than considering one particular inner register (and thus one + particular "outer" register) in isolation, this function really uses + XREGNO as a model for a sequence of isomorphic hard registers. Thus the + function does not check whether adding INFO->offset to XREGNO gives + a valid hard register; even if INFO->offset + XREGNO is out of range, + there might be another register of the same type that is in range. + Likewise it doesn't check whether HARD_REGNO_MODE_OK accepts the new + register, since that can depend on things like whether the final + register number is even or odd. Callers that want to check whether + this particular subreg can be replaced by a simple (reg ...) should + use simplify_subreg_regno. */ + void subreg_get_info (unsigned int xregno, enum machine_mode xmode, unsigned int offset, enum machine_mode ymode, |