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[COMMITTED,GCC13] PR tree-optimization/111694 - Ensure float equivalences include + and - zero.

Message ID b5be9e4b-fb8b-f385-ec81-cc7bede3fb5d@redhat.com
State New
Headers show
Series [COMMITTED,GCC13] PR tree-optimization/111694 - Ensure float equivalences include + and - zero. | expand

Commit Message

Andrew MacLeod Oct. 11, 2023, 8:48 p.m. UTC 
Similar patch which was checked into trunk last week.   slight tweak 
needed as dconstm0 was not exported in gcc 13, otherwise functionally 
the same

Bootstrapped on x86_64-pc-linux-gnu.  pushed.

Andrew
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Patch

commit f0efc4b25cba1bd35b08b7dfbab0f8fc81b55c66
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Mon Oct 9 13:40:15 2023 -0400

    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 2314478d558..e4e75943632 100644
--- a/gcc/gimple-range-cache.cc
+++ b/gcc/gimple-range-cache.cc
@@ -1258,6 +1258,9 @@  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 00000000000..a70b03069dc
--- /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 30a02d3c9d3..fc792a4d5bc 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);
+  REAL_VALUE_TYPE dconstm0 = dconst0;
+  dconstm0.sign = 1;
+  frange zeros (range.type (), dconstm0, dconst0);
+  // If range includes a 0 make sure both signs of zero are included.
+  if (fr.intersect (zeros) && !fr.undefined_p ())
+    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 3177ecb1ad0..6412cbbe98b 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: