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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 | |
| 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
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/rtl.h | 7 | ||||
| -rw-r--r-- | gcc/rtlanal.c | 15 |
3 files changed, 24 insertions, 3 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 3420fb0..9227427 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,10 @@ 2014-09-22 Richard Sandiford <richard.sandiford@arm.com> + * rtl.h (subreg_info): Expand commentary + * rtlanal.c (subreg_get_info): Likewise. + +2014-09-22 Richard Sandiford <richard.sandiford@arm.com> + * hard-reg-set.h (COPY_HARD_REG_SET, COMPL_HARD_REG_SET) (AND_HARD_REG_SET, AND_COMPL_HARD_REG_SET, IOR_HARD_REG_SET) (IOR_COMPL_HARD_REG_SET): Allow the "from" set to be constant. @@ -2875,10 +2875,13 @@ struct subreg_info { /* Offset of first hard register involved in the subreg. */ int offset; - /* Number of hard registers involved in the subreg. */ + /* Number of hard registers involved in the subreg. In the case of + a paradoxical subreg, this is the number of registers that would + be modified by writing to the subreg; some of them may be don't-care + when reading from the subreg. */ int nregs; /* Whether this subreg can be represented as a hard reg with the new - mode. */ + mode (by adding OFFSET to the original hard register). */ bool representable_p; }; 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, |