On 4/19/2021 1:40 AM, Jakub Jelinek via Gcc-patches wrote:
On Sun, Apr 18, 2021 at 08:11:21PM -0400, Andrew MacLeod via Gcc-patches wrote:
--- a/gcc/gimple-range-gori.cc
+++ b/gcc/gimple-range-gori.cc
@@ -29,6 +29,36 @@ along with GCC; see the file COPYING3. If not see
#include "gimple-pretty-print.h"
#include "gimple-range.h"
+// Limit the nested depth thru logical expressions which GORI will build
+// def chains.
+#define LOGICAL_LIMIT 6
Such limits should be in params.def so that users can override them.
+// Return TRUE if GS is a logical && or || expression.
+
+static inline bool
+is_gimple_logical_p (const gimple *gs)
+{
+ // Look for boolean and/or condition.
+ if (gimple_code (gs) == GIMPLE_ASSIGN)
if (is_gimple_assign (gs))
is the normal spelling of this check.
But more importantly, isn't 6 too low for logicals, and wouldn't it be
better to put a cap not on the number of seen logicals, but on how many
SSA_NAMEs are handled in a query? Because it is easy to construct
testcases where the logical limit would not trigger but the operands
of comparisons used in logicals would be thousands of arithmetic/bitwise
statements etc. And it isn't just artificial, we have various examples
of generated tests in bugzilla that typically can't be compiled in
reasonable time at -O2 and need to use -O1 and have huge basic blocks with
very deep chains.
FWIW, the DOM code which tries to do similar things has a 4 level
recursion limit which seemed to catch the vast majority of cases. That
translates into ~8 operands most of the time. So Andrew's check seems
to be in the right ballpark (it's doing something slightly different,
but I think it's close enough to be comparable).
jeff
