Ian Lance Taylor schrieb:
Georg-Johann Lay <avr@xxxxxxxx> writes:
Working out recommendations for a new instruction set architecture (no
silicon yet), I run into the following problem with a port based on
gcc_4_3_3_release: postreload complains
From your description, I would have expected reload to handle this
correctly. I don't know why it didn't. The first place to look would
be to verify that the REG_CLASS_CONTENTS bitmasks are correct. Next,
look at the .greg dump to see if the insn in question required any
reloads. If not, the next step may be to debug find_reloads to find out
why no reloads were required. This can somewhat tedious; you can set a
breakpoint to match the insn UID so that you are looking at the right
insn in find_reloads, but following the loops can still take a while.
Good luck. I've spent many days on this sort of problem.
Ian
Hi Ian,
greg does not generate reloads for the insn in question (the {lshrsi3}),
and find_reloads is never called for it.
I guess the caller should be reload1.c::calculate_needs_all_insns?
When calculate_needs_all_insns runs on the insn the insn looks like this
(other insn numbers than above as I proceed my very work regardless of
the possible bug)
calculate_needs_all_insns[__kernel_rem_pio2:greg(180)]: (insn:HI 409 438
400 17 k_rem_pio2.c:816 (set (reg:SI 566)
(lshiftrt:SI (reg:SI 0 d0 [565])
(const_int 8 [0x8]))) 22 {lshrsi3} (expr_list:REG_EQUIV
(const_int 16777215 [0xffffff])
(expr_list:REG_DEAD (reg:SI 0 d0 [565])
Someone already replaced #1 with d0, a reg of the right class "d". Maybe
a function parameter or return value is propagated.
However, calculate_needs_all_insns decides that there are no reloads
needed. reload1.c:1554 reads:
/* Skip insns that only set an equivalence. */
if (set && REG_P (SET_DEST (set))
&& reg_renumber[REGNO (SET_DEST (set))] < 0
&& (reg_equiv_constant[REGNO (SET_DEST (set))]
|| (reg_equiv_invariant[REGNO (SET_DEST (set))]))
&& reg_equiv_init[REGNO (SET_DEST (set))])
continue;
Before lreg, the insn is tagged REG_EQUAL but lreg then retags it as
REG_EQUIV.
So is the problem in lreg because it says REG_EQUIV?
Or is it wrong to omit REG_EQUIV insns from reload?
Georg-Johann
