The first part of this is a simple type mismatch -- get_max_loop_iterations
returns a widest_int aka max_wide_int -- and I'd have installed it as
obvious. The second part isn't as obvious though. The old code stored
the maximum iterations as:
if (!get_max_loop_iterations (loop, &iter)
|| !iter.fits_shwi ())
iterations_max = const0_rtx;
else
iterations_max = GEN_INT (iter.to_shwi ());
and the new code uses:
if (!get_max_loop_iterations (loop, &iter)
|| !wi::fits_shwi_p (iter))
iterations_max = const0_rtx;
else
iterations_max = immed_wide_int_const (iter, mode);
which includes an extra canonicalisation. I agree it would be good to do
that in principle, but I'm not sure it copes correctly with the case where
the loop iterates 1 << GET_MODE_PRECISION (mode) times. Plus I think the
real fix would be to avoid the host dependence altogether, i.e. get rid
of the fits_shwi_p too.
As it stands, this breaks bfin-elf's pattern, which has:
/* Due to limitations in the hardware (an initial loop count of 0
does not loop 2^32 times) we must avoid to generate a hardware
loops when we cannot rule out this case. */
if (!flag_unsafe_loop_optimizations
&& (unsigned HOST_WIDE_INT) INTVAL (operands[2]) >= 0xFFFFFFFF)
FAIL;
With the sign-extending conversion, this now triggers more often than
it was supposed to.
Since the old "GEN_INT (iter.to_shwi ());" works verbatim in wide-int too,
and since we still use that form in the doloop_begin code, I think we should
just back the immed_wide_int_const out.
Tested on powerpc64-linux-gnu and x86_64-linux-gnu. It fixes some
unwanted testsuite changes in bfin-elf. OK to install?
Thanks,
Richard
Index: gcc/loop-doloop.c
===================================================================
--- gcc/loop-doloop.c 2013-11-02 10:49:37.463178153 +0000
+++ gcc/loop-doloop.c 2013-11-02 10:49:55.927314661 +0000
@@ -549,7 +549,7 @@ doloop_modify (struct loop *loop, struct
{
rtx init;
unsigned level = get_loop_level (loop) + 1;
- wide_int iter;
+ widest_int iter;
rtx iter_rtx;
if (!get_max_loop_iterations (loop, &iter)
@@ -673,7 +673,7 @@ doloop_optimize (struct loop *loop)
|| !wi::fits_shwi_p (iter))
iterations_max = const0_rtx;
else
- iterations_max = immed_wide_int_const (iter, mode);
+ iterations_max = GEN_INT (iter.to_shwi ());
level = get_loop_level (loop) + 1;
/* Generate looping insn. If the pattern FAILs then give up trying
