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Fix GH-24063: SCCP merges 0.0 and -0.0 into a single constant (#24064)
SCCP joins phi values with zend_is_identical(), which compares doubles with ==, so 0.0 and -0.0 count as the same value. A ternary like $n < 0 ? -0.0 : 0.0 then gets folded to whichever constant the first branch held, and the condition disappears. The same thing happens for constant arrays and for elements of partial arrays. The join now compares doubles bitwise (like compact_literals.c already does), recursing into arrays, and falls back to zend_is_identical() for everything else. Fixes GH-24063
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Lines changed: 72 additions & 2 deletions

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‎NEWS‎

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@@ -108,6 +108,8 @@ PHP NEWS
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(David Carlier)
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. Fix multiple incorrect DCE due to unsound escape analysis. (ndossche,
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arnaud-lb)
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. Fixed bug GH-24063 (OPcache optimizer folds `$cond ? -0.0 : 0.0` into a
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single `-0.0` constant). (lazerg)
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- OpenSSL:
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. Fixed stream_socket_enable_crypto() leaving the socket non-blocking

‎Zend/Optimizer/sccp.c‎

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@@ -1946,6 +1946,28 @@ static void sccp_mark_feasible_successors(
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scdf_mark_edge_feasible(scdf, block_num, block->successors[s]);
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}
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/* Unlike zend_is_identical(), this does not treat 0.0 and -0.0 as the same value.
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* Returns int to be usable as compare_func_t. */
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static int sccp_values_differ(const void *p1, const void *p2)
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{
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const zval *a = p1;
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const zval *b = p2;
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if (Z_TYPE_P(a) != Z_TYPE_P(b)) {
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return 1;
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}
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if (Z_TYPE_P(a) == IS_DOUBLE) {
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return memcmp(&Z_DVAL_P(a), &Z_DVAL_P(b), sizeof(double)) != 0;
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}
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if (Z_TYPE_P(a) == IS_ARRAY) {
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return Z_ARRVAL_P(a) != Z_ARRVAL_P(b)
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&& zend_hash_compare(Z_ARRVAL_P(a), Z_ARRVAL_P(b), sccp_values_differ, 1) != 0;
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}
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ZEND_ASSERT(IS_PARTIAL_ARRAY(a) || IS_PARTIAL_OBJECT(a)
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|| ((1 << Z_TYPE_P(a)) & (MAY_BE_UNDEF|MAY_BE_NULL|MAY_BE_BOOL|MAY_BE_LONG|MAY_BE_STRING)));
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return !zend_is_identical(a, b);
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}
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static void join_hash_tables(HashTable *ret, HashTable *ht1, HashTable *ht2)
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{
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zend_ulong index;
@@ -1958,7 +1980,7 @@ static void join_hash_tables(HashTable *ret, HashTable *ht1, HashTable *ht2)
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} else {
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val2 = zend_hash_index_find(ht2, index);
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}
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if (val2 && zend_is_identical(val1, val2)) {
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if (val2 && !sccp_values_differ(val1, val2)) {
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if (key) {
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val1 = zend_hash_add_new(ret, key, val1);
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} else {
@@ -2026,7 +2048,7 @@ static void join_phi_values(zval *a, zval *b, bool escape) {
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zval_ptr_dtor_nogc(a);
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MAKE_BOT(a);
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}
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} else if (!zend_is_identical(a, b)) {
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} else if (sccp_values_differ(a, b)) {
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if (join_partial_arrays(a, b) == FAILURE) {
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zval_ptr_dtor_nogc(a);
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MAKE_BOT(a);

‎ext/opcache/tests/opt/gh24063.phpt‎

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@@ -0,0 +1,46 @@
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--TEST--
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GH-24063 (SCCP merges 0.0 and -0.0 into a single constant)
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--EXTENSIONS--
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opcache
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--INI--
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opcache.enable=1
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opcache.enable_cli=1
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opcache.optimization_level=-1
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--FILE--
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<?php
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function scalar(float $n): float
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{
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$r = $n < 0 ? -0.0 : 0.0;
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return $r;
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}
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function arr(float $n): array
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{
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$r = $n < 0 ? [-0.0] : [0.0];
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return $r;
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}
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function partial(float $n, $x): float
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{
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$a = ['x' => $x];
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if ($n < 0) {
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$a['k'] = -0.0;
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} else {
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$a['k'] = 0.0;
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}
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return $a['k'];
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}
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var_dump(scalar(1.0), scalar(-1.0));
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var_dump(arr(1.0)[0], arr(-1.0)[0]);
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var_dump(partial(1.0, 1), partial(-1.0, 1));
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?>
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--EXPECT--
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float(0)
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float(-0)
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float(0)
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float(-0)
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float(0)
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float(-0)

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