File 2003-beam_emu-Slightly-optimize-the-bxor-2-oper... of Package erlang

Overview Repositories Revisions Requests Users Attributes Meta

File 2003-beam_emu-Slightly-optimize-the-bxor-2-operator.patch of Package erlang (Revision aa120d3233f613ad478314c3181372c5)

Currently displaying revision aa120d3233f613ad478314c3181372c5 , Show latest

From bb89d065dbe47554c0cb929d244e0d38cad52e65 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 7 Apr 2017 12:04:11 +0200
Subject: [PATCH] beam_emu: Slightly optimize the bxor/2 operator

bxor is used in the rand module, so even small optimizations
could be worthwile.

Suggested by Raimo Niskanen.
---
 erts/emulator/beam/beam_emu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 9a91fdce0..6010c17c1 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -3044,10 +3044,12 @@ do {						\
      GetArg2(2, Op1, Op2);
      if (is_both_small(Op1, Op2)) {
 	 /*
-	  * We could extract the tag from one argument, but a tag extraction
-	  * could mean a shift.  Therefore, play it safe here.
+          * TAG ^ TAG == 0.
+          *
+          * Therefore, we perform the XOR operation on the tagged values,
+          * and OR in the tag bits.
 	  */
-	 Eterm result = make_small(signed_val(Op1) ^ signed_val(Op2));
+	 Eterm result = (Op1 ^ Op2) | make_small(0);
 	 StoreBifResult(4, result);
      }
      DO_OUTLINED_ARITH_2(bxor, Op1, Op2);
-- 
2.12.2

Places

File 2003-beam_emu-Slightly-optimize-the-bxor-2-operator.patch of Package erlang (Revision aa120d3233f613ad478314c3181372c5)

Places