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| author | J"orn Rennecke <amylaar@cygnus.co.uk> | 1999-02-02 11:52:00 +0000 |
|---|---|---|
| committer | Joern Rennecke <amylaar@gcc.gnu.org> | 1999-02-02 11:52:00 +0000 |
| commit | 7221f080227636b16826313a5148999c777d8b67 (patch) | |
| tree | 9289d57fce739fc33850e22a887d052e865e60fb /gcc | |
| parent | e77dbc56f903af3ca76d16c29d8061385cf80e52 (diff) | |
| download | gcc-7221f080227636b16826313a5148999c777d8b67.zip gcc-7221f080227636b16826313a5148999c777d8b67.tar.gz gcc-7221f080227636b16826313a5148999c777d8b67.tar.bz2 | |
(recombine_givs): Don't use a giv that's likely to be dead to derive others.
* (recombine_givs): Don't use a giv that's likely to be dead to
derive others.
* loop.c (recombine_givs): Fix test for lifetime overlaps / loop
wrap around when deriving givs.
From-SVN: r24967
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 8 | ||||
| -rw-r--r-- | gcc/loop.c | 26 |
2 files changed, 29 insertions, 5 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 89fd8ab..cf302bc 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +Tue Feb 2 19:48:29 1999 J"orn Rennecke <amylaar@cygnus.co.uk> + + * (recombine_givs): Don't use a giv that's likely to be dead to + derive others. + + * loop.c (recombine_givs): Fix test for lifetime overlaps / loop + wrap around when deriving givs. + Mon Feb 1 20:00:40 1999 Richard Henderson <rth@cygnus.com> * recog.c (check_asm_operands): Treat indeterminate operand ok @@ -7293,16 +7293,28 @@ recombine_givs (bl, loop_start, loop_end, unroll_p) continue; if (! last_giv) { - last_giv = v; - life_start = stats[i].start_luid; - life_end = stats[i].end_luid; + /* Don't use a giv that's likely to be dead to derive + others - that would be likely to keep that giv alive. */ + if (! v->maybe_dead || v->combined_with) + { + last_giv = v; + life_start = stats[i].start_luid; + life_end = stats[i].end_luid; + } continue; } /* Use unsigned arithmetic to model loop wrap around. */ if (((unsigned) stats[i].start_luid - life_start >= (unsigned) life_end - life_start) && ((unsigned) stats[i].end_luid - life_start - >= (unsigned) life_end - life_start) + > (unsigned) life_end - life_start) + /* Check that the giv insn we're about to use for deriving + precedes all uses of that giv. Note that initializing the + derived giv would defeat the purpose of reducing register + pressure. + ??? We could arrange to move the insn. */ + && ((unsigned) stats[i].end_luid - INSN_LUID (loop_start) + > (unsigned) stats[i].start_luid - INSN_LUID (loop_start)) && rtx_equal_p (last_giv->mult_val, v->mult_val) /* ??? Could handle libcalls, but would need more logic. */ && ! find_reg_note (v->insn, REG_RETVAL, NULL_RTX) @@ -7312,7 +7324,11 @@ recombine_givs (bl, loop_start, loop_end, unroll_p) don't have this detailed control flow information. N.B. since last_giv will be reduced, it is valid anywhere in the loop, so we don't need to check the - validity of last_giv. */ + validity of last_giv. + We rely here on the fact that v->always_executed implies that + there is no jump to someplace else in the loop before the + giv insn, and hence any insn that is executed before the + giv insn in the loop will have a lower luid. */ && (v->always_executed || ! v->combined_with) && (sum = express_from (last_giv, v)) /* Make sure we don't make the add more expensive. ADD_COST |