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.

1 files changed, 3 insertions, 0 deletions

diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
index 9175651..9d3fe89 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