From: Andrew MacLeod <amacleod@redhat.com>
Date: Mon, 9 Oct 2023 14:15:07 +0000 (-0400)
Subject: Ensure float equivalences include + and - zero.
X-Git-Tag: basepoints/gcc-15~5619
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b0892b1fc637fadf14d7016858983bc5776a1e69;p=thirdparty%2Fgcc.git

Ensure float equivalences include + and - zero.

A floating point equivalence may not properly reflect both signs of
zero, so be pessimsitic and ensure both signs are included.

	PR tree-optimization/111694
	gcc/
	* gimple-range-cache.cc (ranger_cache::fill_block_cache): Adjust
	equivalence range.
	* value-relation.cc (adjust_equivalence_range): New.
	* value-relation.h (adjust_equivalence_range): New prototype.

	gcc/testsuite/
	* gcc.dg/pr111694.c: New.
---

diff --git a/gcc/gimple-range-cache.cc b/gcc/gimple-range-cache.cc
index 3c819933c4ed..89c0845457d0 100644
--- a/gcc/gimple-range-cache.cc
+++ b/gcc/gimple-range-cache.cc
@@ -1470,6 +1470,9 @@ ranger_cache::fill_block_cache (tree name, basic_block bb, basic_block def_bb)
 		{
 		  if (rel != VREL_EQ)
 		    range_cast (equiv_range, type);
+		  else
+		    adjust_equivalence_range (equiv_range);
+
 		  if (block_result.intersect (equiv_range))
 		    {
 		      if (DEBUG_RANGE_CACHE)
diff --git a/gcc/testsuite/gcc.dg/pr111694.c b/gcc/testsuite/gcc.dg/pr111694.c
new file mode 100644
index 000000000000..a70b03069dce
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr111694.c
@@ -0,0 +1,19 @@
+/* PR tree-optimization/111009 */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#define signbit(x) __builtin_signbit(x)
+
+static void test(double l, double r)
+{
+  if (l == r && (signbit(l) || signbit(r)))
+    ;
+  else
+    __builtin_abort();
+}
+
+int main()
+{
+  test(0.0, -0.0);
+}
+
diff --git a/gcc/value-relation.cc b/gcc/value-relation.cc
index a2ae39692a61..0326fe7cde62 100644
--- a/gcc/value-relation.cc
+++ b/gcc/value-relation.cc
@@ -183,6 +183,25 @@ relation_transitive (relation_kind r1, relation_kind r2)
   return relation_kind (rr_transitive_table[r1][r2]);
 }
 
+// When one name is an equivalence of another, ensure the equivalence
+// range is correct.  Specifically for floating point, a +0 is also
+// equivalent to a -0 which may not be reflected.  See PR 111694.
+
+void
+adjust_equivalence_range (vrange &range)
+{
+  if (range.undefined_p () || !is_a<frange> (range))
+    return;
+
+  frange fr = as_a<frange> (range);
+  // If range includes 0 make sure both signs of zero are included.
+  if (fr.contains_p (dconst0) || fr.contains_p (dconstm0))
+    {
+      frange zeros (range.type (), dconstm0, dconst0);
+      range.union_ (zeros);
+    }
+ }
+
 // This vector maps a relation to the equivalent tree code.
 
 static const tree_code relation_to_code [VREL_LAST] = {
diff --git a/gcc/value-relation.h b/gcc/value-relation.h
index be6e277421bf..31d489086789 100644
--- a/gcc/value-relation.h
+++ b/gcc/value-relation.h
@@ -91,6 +91,9 @@ inline bool relation_equiv_p (relation_kind r)
 
 void print_relation (FILE *f, relation_kind rel);
 
+// Adjust range as an equivalence.
+void adjust_equivalence_range (vrange &range);
+
 class relation_oracle
 {
 public: