On Thu, Dec 07, 2023 at 09:36:22AM +0100, Jakub Jelinek wrote:
> So, one way to fix the LRA issue would be just to use
> lra_insn_recog_data_len = index * 3U / 2;
> if (lra_insn_recog_data_len <= index)
> lra_insn_recog_data_len = index + 1;
> basically do what vec.cc does. I thought we can do better for
> both vec.cc and LRA on 64-bit hosts even without growing the allocated
> counters, but now that I look at it again, perhaps we can't.
> The above overflows already with original alloc or lra_insn_recog_data_len
> 0x55555556, where 0x5555555 * 3U / 2 is still 0x7fffffff
> and so representable in the 32-bit, but 0x55555556 * 3U / 2 is
> 1. I thought (and the patch implements it) that we could use
> alloc * (size_t) 3 / 2 so that on 64-bit hosts it wouldn't overflow
> that quickly, but 0x55555556 * (size_t) 3 / 2 there is 0x80000001
> which is still ok in unsigned, but given that vec.h then stores the
> counter into unsigned m_alloc:31; bit-field, it is too much.
>
> The patch below is what I've actually bootstrapped/regtested on
> x86_64-linux and i686-linux, but given the above I think I should drop
> the vec.cc hunk and change (size_t) 3 in the LRA hunk to 3U.
Here is so far untested adjusted patch, which does the computation
just in unsigned int rather than size_t, because doing it in size_t
wouldn't improve things.
2023-12-07 Jakub Jelinek <ja...@redhat.com>
PR middle-end/112411
* params.opt (-param=min-nondebug-insn-uid=): Add
IntegerRange(0, 1073741824).
* lra.cc (check_and_expand_insn_recog_data): Use 3U rather than 3
in * 3 / 2 computation and if the result is smaller or equal to
index, use index + 1.
* gcc.dg/params/blocksort-part.c: Add dg-skip-if for
--param min-nondebug-insn-uid=1073741824.
--- gcc/params.opt.jj 2023-11-02 07:49:18.010852541 +0100
+++ gcc/params.opt 2023-12-06 18:55:57.045420935 +0100
@@ -779,7 +779,7 @@ Common Joined UInteger Var(param_min_loo
The minimum threshold for probability of semi-invariant condition statement to
trigger loop split.
-param=min-nondebug-insn-uid=
-Common Joined UInteger Var(param_min_nondebug_insn_uid) Param
+Common Joined UInteger Var(param_min_nondebug_insn_uid) Param IntegerRange(0,
1073741824)
The minimum UID to be used for a nondebug insn.
-param=min-size-for-stack-sharing=
--- gcc/lra.cc.jj 2023-12-05 13:17:29.642260866 +0100
+++ gcc/lra.cc 2023-12-06 19:52:01.759241999 +0100
@@ -768,7 +768,9 @@ check_and_expand_insn_recog_data (int in
if (lra_insn_recog_data_len > index)
return;
old = lra_insn_recog_data_len;
- lra_insn_recog_data_len = index * 3 / 2 + 1;
+ lra_insn_recog_data_len = index * 3U / 2;
+ if (lra_insn_recog_data_len <= index)
+ lra_insn_recog_data_len = index + 1;
lra_insn_recog_data = XRESIZEVEC (lra_insn_recog_data_t,
lra_insn_recog_data,
lra_insn_recog_data_len);
--- gcc/testsuite/gcc.dg/params/blocksort-part.c.jj 2020-01-12
11:54:37.463397567 +0100
+++ gcc/testsuite/gcc.dg/params/blocksort-part.c 2023-12-07
08:46:11.656974144 +0100
@@ -1,4 +1,5 @@
/* { dg-skip-if "AArch64 does not support these bounds." { aarch64*-*-* } {
"--param stack-clash-protection-*" } } */
+/* { dg-skip-if "For 32-bit hosts such param is too much and even for 64-bit
might require hundreds of GB of RAM" { *-*-* } { "--param
min-nondebug-insn-uid=1073741824" } } */
/*-------------------------------------------------------------*/
/*--- Block sorting machinery ---*/
Jakub
