From: Richard Biener <rguenther@suse.de>
Date: Sun, 23 Jun 2024 12:37:53 +0000 (+0200)
Subject: tree-optimization/115599 - reassoc qsort comparator issue
X-Git-Tag: basepoints/gcc-16~7976
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ae13af26060eb686418ea9c9d455cd665049402d;p=thirdparty%2Fgcc.git

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 4d9f5216d4c..d74352268b5 100644
--- 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