2017-01-10 Nathan Sidwell <nathan@acm.org>
Nicolai Stange <nicstange@gmail.com>
* combine.c (try_combine): Don't ignore result of overlap checking
loop. Combine overlap & asm check into single loop.
===================================================================
@@ -2785,22 +2785,24 @@ try_combine (rtx_insn *i3, rtx_insn *i2,
(Besides, reload can't handle output reloads for this.)
The problem can also happen if the dest of I3 is a memory ref,
- if another dest in I2 is an indirect memory ref. */
- for (i = 0; i < XVECLEN (p2, 0); i++)
- if ((GET_CODE (XVECEXP (p2, 0, i)) == SET
- || GET_CODE (XVECEXP (p2, 0, i)) == CLOBBER)
- && reg_overlap_mentioned_p (SET_DEST (PATTERN (i3)),
- SET_DEST (XVECEXP (p2, 0, i))))
- break;
+ if another dest in I2 is an indirect memory ref.
- /* Make sure this PARALLEL is not an asm. We do not allow combining
+ Neither can this PARALLEL be not an asm. We do not allow combining
that usually (see can_combine_p), so do not here either. */
- for (i = 0; i < XVECLEN (p2, 0); i++)
- if (GET_CODE (XVECEXP (p2, 0, i)) == SET
- && GET_CODE (SET_SRC (XVECEXP (p2, 0, i))) == ASM_OPERANDS)
- break;
+ bool ok = true;
+ for (i = 0; ok && i < XVECLEN (p2, 0); i++)
+ {
+ if ((GET_CODE (XVECEXP (p2, 0, i)) == SET
+ || GET_CODE (XVECEXP (p2, 0, i)) == CLOBBER)
+ && reg_overlap_mentioned_p (SET_DEST (PATTERN (i3)),
+ SET_DEST (XVECEXP (p2, 0, i))))
+ ok = false;
+ else if (GET_CODE (XVECEXP (p2, 0, i)) == SET
+ && GET_CODE (SET_SRC (XVECEXP (p2, 0, i))) == ASM_OPERANDS)
+ ok = false;
+ }
- if (i == XVECLEN (p2, 0))
+ if (ok)
for (i = 0; i < XVECLEN (p2, 0); i++)
if (GET_CODE (XVECEXP (p2, 0, i)) == SET
&& SET_DEST (XVECEXP (p2, 0, i)) == SET_SRC (PATTERN (i3)))
This patch addresses an issue Nicolai found while browsing combine.c. He noticed some checking code that looked like: for (i = 0; i < NUM_ARGS; i++) if (!cond) break; for (i = 0; i < NUM_ARGS; i++) if (!other_cond) break; if (i == NUM_ARGS) do_the_thing; the intent is that both cond and other_cond are true for all args, but the first loop's negative result (i != NUM_ARGS) is being ignored. This patch fixes that problem, and I took the opportunity to merge both loops into a single loop: ok = true; for (i = 0; ok && i < NUM_ARGS; i++) if (!cond || !other_cond) ok = false; if (ok) do_the_thing; Segher commented on IRC that a single loop would be slower. I disagree. These days the optimizer is smart enough to turn that boolean logic into direct control flow, and a single loop is certainly smaller code (I checked). The only case that might be faster would be an early out if the first loop resulted in a negative. But I doubt that's significant, particularly as the first loop's check is the more expensive one and the second loops check is very cheap. booted & tested on x86_64-linux. Thanks to Nic for finding this problem and helping test it. nathan -- Nathan Sidwell