From 889dbf81def0986e4569841d64a7f3882808ee07 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?= <egil@erlang.org>
Date: Wed, 6 May 2015 15:17:18 +0200
Subject: erts: Don't let the compiler optimize pos. zero fix

---
 erts/emulator/beam/erl_arith.c |  5 +++++
 erts/emulator/beam/global.h    |  3 +++
 erts/emulator/beam/utils.c     | 12 ++++++++----
 3 files changed, 16 insertions(+), 4 deletions(-)

(limited to 'erts')

diff --git a/erts/emulator/beam/erl_arith.c b/erts/emulator/beam/erl_arith.c
index 5150a8a507..47d516534f 100644
--- a/erts/emulator/beam/erl_arith.c
+++ b/erts/emulator/beam/erl_arith.c
@@ -2048,3 +2048,8 @@ Eterm erts_gc_bnot(Process* p, Eterm* reg, Uint live)
     }
     return result;
 } 
+
+/* Needed to remove compiler optimization */
+double erts_get_positive_zero_float() {
+    return 0.0f;
+}
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 40b043d1cc..54fba9274f 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -867,6 +867,9 @@ void print_process_info(int, void *, Process*);
 void info(int, void *);
 void loaded(int, void *);
 
+/* erl_arith.c */
+double erts_get_positive_zero_float(void);
+
 /* config.c */
 
 __decl_noreturn void __noreturn erl_exit(int n, char*, ...);
diff --git a/erts/emulator/beam/utils.c b/erts/emulator/beam/utils.c
index 8f6335d5dd..51de3528be 100644
--- a/erts/emulator/beam/utils.c
+++ b/erts/emulator/beam/utils.c
@@ -958,7 +958,8 @@ tail_recur:
             FloatDef ff;
             GET_DOUBLE(term, ff);
             if (ff.fd == 0.0f) {
-                ff.fd = 0.0f; /* ensure pos. 0.0 */
+                /* ensure positive 0.0 */
+                ff.fd = erts_get_positive_zero_float();
             }
             hash = hash*FUNNY_NUMBER6 + (ff.fw[0] ^ ff.fw[1]);
             break;
@@ -1477,7 +1478,8 @@ make_hash2(Eterm term)
 		FloatDef ff;
 		GET_DOUBLE(term, ff);
                 if (ff.fd == 0.0f) {
-                    ff.fd = 0.0f; /* ensure pos. 0.0 */
+                    /* ensure positive 0.0 */
+                    ff.fd = erts_get_positive_zero_float();
                 }
 #if defined(WORDS_BIGENDIAN) || defined(DOUBLE_MIDDLE_ENDIAN)
 		UINT32_HASH_2(ff.fw[0], ff.fw[1], HCONST_12);
@@ -1899,7 +1901,8 @@ make_internal_hash(Eterm term)
 		FloatDef ff;
 		GET_DOUBLE(term, ff);
                 if (ff.fd == 0.0f) {
-                    ff.fd = 0.0f; /* ensure pos. 0.0 */
+                    /* ensure positive 0.0 */
+                    ff.fd = erts_get_positive_zero_float();
                 }
 		UINT32_HASH_2(ff.fw[0], ff.fw[1], HCONST_12);
 		goto pop_next;
@@ -2087,7 +2090,8 @@ tail_recur:
             FloatDef ff;
             GET_DOUBLE(term, ff);
             if (ff.fd == 0.0f) {
-                ff.fd = 0.0f; /* ensure pos. 0.0 */
+                /* ensure positive 0.0 */
+                ff.fd = erts_get_positive_zero_float();
             }
             hash = hash*FUNNY_NUMBER6 + (ff.fw[0] ^ ff.fw[1]);
 	}
-- 
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