On 6/16/21 5:41 AM, Maxim Kuvyrkov wrote:
On 15 Jun 2021, at 00:07, Andrew MacLeod via Gcc-patches
wrote:
As mentioned in the Text from the PR:
"When a range is being calculated for an ssa-name, the propagation process often goes
along back edges. These back edges sometime require other ssa-names which have not be
processed yet. These are flagged as "poor values" and when propagation is done, we
visit the list of poor values, calculate them, and see if that may result if a better range
for the original ssa-name.
The problem is that calculating these poor values may also spawn another set of
requests since the block at the far end of the back edge has not been processed
yet... its highly likely that some additional unprocessed ssa-names are used in
the calculation of that name, but typically they do not affect the current
range in a significant way.
Thus we mostly we care about the first order effect only. It turns out to be
very rare that a 2nd order effect on a back edge affects anything that we don't
catch later.
This patch turns off poor-value tagging when looking up the first order values,
thus avoiding the 2nd order and beyond cascading effects.
I haven't found a test case we miss yet because of this change, yet it probably
resolves a number of the outstanding compilation problems in a significant way.
I think this will probably apply to gcc 11 in some form as well, so I'll look at an
equivalent patch for there."
This patch simplifies the enable_new_value routines.. replacing the
enable/disable with an enable with flag routine, which returns the previous
value.This lets us change the mode and then set it back to what it was before.
Seems better in general.
Then disables new values for 2nd+ order effects. GCC11 patch forthcoming.
Bootstraps on x86_64-pc-linux-gnu, no regressions. pushed.
Andrew
Hi Andrew,
This causes bootstrap-with-ubsan failure on at least aarch64-linux-gnu, likely,
others:
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 48, which is not a valid value for type 'bool'
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 48, which is not a valid value for type 'bool'
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 32, which is not a valid value for type 'bool'
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 48, which is not a valid value for type 'bool'
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 32, which is not a valid value for type 'bool'
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 48, which is not a valid value for type 'bool'
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 32, which is not a valid value for type 'bool'
# 00:42:32
/home/tcwg-buildslave/workspace/tcwg_gnu_0/abe/snapshots/gcc.git~master/gcc/gimple-range-cache.cc:757:8:
runtime error: load of value 32, which is not a valid value for type 'bool'
@@ -748,21 +748,15 @@ ranger_cache::dump (FILE *f)
fprintf (f, "\n");
}
-// Allow the cache to flag and query new values when propagation is forced
-// to use an unknown value.
+// Allow or disallow the cache to flag and query new values when propagation
+// is forced to use an unknown value. The previous state is returned.
-void
-ranger_cache::enable_new_values ()
-{
- m_new_value_p = true;
-}
-
-// Disable new value querying.
-
-void
-ranger_cache::disable_new_values ()
+bool
+ranger_cache::enable_new_values (bool state)
{
- m_new_value_p = false;
+ bool ret = m_new_value_p;
I think changing this to
bool ret = (bool) m_new_value_p;
might be enough, but you know this code better.
Would you please take a look at this?
+ m_new_value_p = state;
+ return ret;
}
// Dump the caches for basic block BB to file F.
Thanks,
Huh, not sure why that would matter since m_new_value_p is a bool.
My guess is (and this bugged me after I checked it in, just haven't
gotten to it yet), is that this is initialized in the constructor with a
call, and the return value ignored. Which means there is techincally a
load of an uninitialized value, which is then ignored. but the load may
happen. Im going to guess thats the issue. It needs fixing anyway
Im testing this fix, which i will check in. See if that solves the
ubsan issue.
@@ -727,7 +727,7 @@ ranger_cache::ranger_cache (gimple_ranger &q) :
query (q)
if (bb)
