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* [gcc r12-5000] path solver: Avoid recalculating ranges already in the cache.
@ 2021-11-08 15:08 Aldy Hernandez
0 siblings, 0 replies; only message in thread
From: Aldy Hernandez @ 2021-11-08 15:08 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:18546941ae4c56cd9240d2dc2ca2806e01eb6fb7
commit r12-5000-g18546941ae4c56cd9240d2dc2ca2806e01eb6fb7
Author: Aldy Hernandez <aldyh@redhat.com>
Date: Mon Nov 8 12:13:33 2021 +0100
path solver: Avoid recalculating ranges already in the cache.
The problem here is an ordering issue with a path that starts
with 19->3:
<bb 3> [local count: 916928331]:
# value_20 = PHI <value_17(19), value_7(D)(17)>
# n_27 = PHI <n_16(19), 1(17)>
n_16 = n_27 + 4;
value_17 = value_20 / 10000;
if (value_20 > 42949672959999)
goto <bb 19>; [89.00%]
else
goto <bb 4>; [11.00%]
The problem here is that both value_17 and value_20 are in the set of
imports we must pre-calculate. The value_17 name occurs first in the
bitmap, so we try to resolve it first, which causes us to recursively
solve the value_20 range. We do so correctly and put them both in the
cache. However, when we try to solve value_20 from the bitmap, we
ignore that it already has a cached entry and try to resolve the PHI
with the wrong value of value_17:
# value_20 = PHI <value_17(19), value_7(D)(17)>
The right thing to do is to avoid recalculating definitions already
solved.
Regstrapped and checked for # threads before and after on x86-64 Linux.
gcc/ChangeLog:
PR tree-optimization/103120
* gimple-range-path.cc (path_range_query::range_defined_in_block):
Bail if there's a cache entry.
gcc/testsuite/ChangeLog:
* gcc.dg/pr103120.c: New test.
Diff:
---
gcc/gimple-range-path.cc | 3 +++
gcc/testsuite/gcc.dg/pr103120.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)
diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
index 9175651e896..9d3fe89185e 100644
--- a/gcc/gimple-range-path.cc
+++ b/gcc/gimple-range-path.cc
@@ -300,6 +300,9 @@ path_range_query::range_defined_in_block (irange &r, tree name, basic_block bb)
if (def_bb != bb)
return false;
+ if (get_cache (r, name))
+ return true;
+
if (gimple_code (def_stmt) == GIMPLE_PHI)
ssa_range_in_phi (r, as_a<gphi *> (def_stmt));
else
diff --git a/gcc/testsuite/gcc.dg/pr103120.c b/gcc/testsuite/gcc.dg/pr103120.c
new file mode 100644
index 00000000000..b680a6c0fb0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr103120.c
@@ -0,0 +1,33 @@
+// { dg-do run }
+// { dg-options "-O2" }
+
+#define radix 10
+__INT32_TYPE__ numDigits(__UINT64_TYPE__ value)
+{
+ __INT32_TYPE__ n = 1;
+ while (value > __UINT32_MAX__)
+ {
+ n += 4;
+ value /= radix * radix * radix * radix;
+ }
+ __UINT32_TYPE__ v = (__UINT32_TYPE__)value;
+ while (1)
+ {
+ if (v < radix)
+ return n;
+ if (v < radix * radix)
+ return n + 1;
+ if (v < radix * radix * radix)
+ return n + 2;
+ if (v < radix * radix * radix * radix)
+ return n + 3;
+ n += 4;
+ v /= radix * radix * radix * radix;
+ }
+}
+
+int main()
+{
+ if (numDigits(__UINT64_MAX__) != 20)
+ __builtin_abort();
+}
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