tree-optimization/115599 - reassoc qsort comparator issue

The compare_repeat_factors comparator fails qsort checking eventually
because it uses rf2->rank - rf1->rank to compare unsigned numbers
which causes issues for ranks that interpret negative as signed.

Fixed by re-writing the obvious way.  I've also fixed the count
comparison which suffers from truncation as count is 64bit signed
while the comparator result is 32bit int (that's a lot less likely
to hit in practice though).

The testcase from the PR is too large to include.

	PR tree-optimization/115599
	* tree-ssa-reassoc.cc (compare_repeat_factors): Use explicit
	compares to avoid truncations.

diff --git a/gcc/tree-ssa-reassoc.cc b/gcc/tree-ssa-reassoc.cc
index 4d9f5216d4cbb43af9118156335425c826f4e290..d74352268b5d502562d153ceac1807524568a097 100644 (file)
--- a/gcc/tree-ssa-reassoc.cc
+++ b/gcc/tree-ssa-reassoc.cc
@@ -6414,10 +6414,17 @@ compare_repeat_factors (const void *x1, const void *x2)
   const repeat_factor *rf1 = (const repeat_factor *) x1;
   const repeat_factor *rf2 = (const repeat_factor *) x2;
 
-  if (rf1->count != rf2->count)
-    return rf1->count - rf2->count;
+  if (rf1->count < rf2->count)
+    return -1;
+  else if (rf1->count > rf2->count)
+    return 1;
+
+  if (rf1->rank < rf2->rank)
+    return 1;
+  else if (rf1->rank > rf2->rank)
+    return -1;
 
-  return rf2->rank - rf1->rank;
+  return 0;
 }
 
 /* Look for repeated operands in OPS in the multiply tree rooted at