This patch fixes intransitive comparison in reload_pseudo_compare_func.
Imagine the following
situation:
1) bitmap_bit_p is unset for A and B but set for C
2) A < B (due to early ira_reg_class_max_nregs comparison)
3) B < C (due to following regno_assign_info comparison)
It may then easily happen that A > C (due to regno_assign_info
comparison) which violates the transitiveness requirement of total ordering.
Unfortunately I'm not sure how to properly fix this so Cc-ing Vladimir
for help.
/Yury
From 83da5d11c4f013dd14c1ea0c1722c108d80f58ed Mon Sep 17 00:00:00 2001
From: Yury Gribov <tetra2...@gmail.com>
Date: Sat, 12 Dec 2015 10:08:45 +0300
Subject: [PATCH 3/5] "Fix" intransitive comparison in
reload_pseudo_compare_func.
2015-12-17 Yury Gribov <tetra2...@gmail.com>
* lra-assigns.c (reload_pseudo_compare_func):
Make transitive.
Error message:
Dec 10 00:33:18 yugr-ubuntu1404 : cc1plus[612]: qsort: comparison function is not transitive (comparison function 0x87bc50 (/home/yugr/build/gcc-4.9.3-patched-bootstrap/gcc/cc1plus+47bc50), called from 0x87d25c (/home/yugr/build/gcc-4.9.3-patched-bootstrap/gcc/cc1plus+47d25c), cmdline is "/home/yugr/build/gcc-4.9.3-patched-bootstrap/./gcc/cc1plus -quiet -nostdinc++ -I . -I /home/yugr/src/gcc-4.9.3-patched/libsanitizer/tsan -I .. -I /home/yugr/src/gcc-4.9.3-patched/libsanitizer -I /home/yugr/src/gcc-4.9.3-patched/libsanitizer/include -I ../../libstdc++-v3/include -I ../../libstdc++-v3/include/x86_64-unknown-linux-gnu -I /home/yugr/src/gcc-4.9.3-patched/libsanitizer/../libstdc++-v3/libsupc++ -imultiarch x86_64-linux-gnu -iprefix /home/yugr/build/gcc-4.9.3-patched-bootstrap/gcc/../lib/gcc/x86_64-unknown-linux-gnu/4.9.3/ -isystem /home/yugr/build/gcc-4.9.3-patched-bootstrap/./gcc/include -isystem /home/yugr/build/gcc-4.9.3-patched-bootstrap/./gcc/include-fixed -MD .libs/tsan_interface_atomic.d -MF .deps/tsan_interface_atomic.Tpo -MP -MT tsan_interface_atomic.lo -D_GNU_SOURCE -D _GNU_SOURCE -D _DEBUG -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D _GNU_SOURCE -D PIC -isystem /home/yugr/install/gcc-4.9.3/x86_64-unknown-linux-gnu/include -isystem /home/yugr/install/gcc-4.9.3/x86_64-unknown-linux-gnu/sys-include /home/yugr/src/gcc-4.9.3-patched/libsanitizer/tsan/tsan_interface_atomic.cc -quiet -dumpbase tsan_interface_atomic.cc -mtune=generic -march=x86-64 -auxbase-strip .libs/tsan_interface_atomic.o -g -O2 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wpedantic -Wno-long-long -Wno-variadic-macros -fno-builtin -fno-exceptions -fno-rtti -fomit-frame-pointer -funwind-tables -fvisibility=hidden -fPIC -o /tmp/cc3IPd7A.s")
---
gcc/lra-assigns.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/gcc/lra-assigns.c b/gcc/lra-assigns.c
index 2a9ff21..94f3e66 100644
--- a/gcc/lra-assigns.c
+++ b/gcc/lra-assigns.c
@@ -208,12 +208,7 @@ reload_pseudo_compare_func (const void *v1p, const void *v2p)
return diff;
if ((diff
= (ira_reg_class_max_nregs[cl2][lra_reg_info[r2].biggest_mode]
- - ira_reg_class_max_nregs[cl1][lra_reg_info[r1].biggest_mode])) != 0
- /* The code below executes rarely as nregs == 1 in most cases.
- So we should not worry about using faster data structures to
- check reload pseudos. */
- && ! bitmap_bit_p (&non_reload_pseudos, r1)
- && ! bitmap_bit_p (&non_reload_pseudos, r2))
+ - ira_reg_class_max_nregs[cl1][lra_reg_info[r1].biggest_mode])) != 0)
return diff;
if ((diff = (regno_assign_info[regno_assign_info[r2].first].freq
- regno_assign_info[regno_assign_info[r1].first].freq)) != 0)
--
1.9.1
