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authorBjörn Gustavsson <[email protected]>2010-04-23 10:04:42 +0200
committerBjörn Gustavsson <[email protected]>2010-05-11 08:54:26 +0200
commit9c91901e8e57fd6366fd966e754a62a8a205c000 (patch)
tree9c8299fcb4752ec79e32d20d1bd4c56f47b32a94 /erts/emulator
parentf7829c91d742f1daea27b7ff5d8dcb5f262fd3a9 (diff)
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erts: Implement recv_mark/1 and recv_set/1 for real
The recv_mark/1 instruction will both save the current position in the message queue and a mark (the address of the loop_rec/2 instruction just following the recv_set/1 instruction). The recv_mark/1 instruction will only use the saved position if the mark is correct. The reason for saving and verifying the mark is that the compiler does not need to guarantee that no other receive instruction can be executed in between the recv_mark/1 and recv_set/1 instructions (the mark will be cleared by the remove_message/0 instruction when a message is removed from the message queue). That means that arbitrary function calls in between those instruction can be allowed.
Diffstat (limited to 'erts/emulator')
-rw-r--r--erts/emulator/beam/beam_emu.c32
-rw-r--r--erts/emulator/beam/erl_message.h8
-rw-r--r--erts/emulator/beam/ops.tab7
3 files changed, 45 insertions, 2 deletions
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 5b2f032afc..ee8ba54cb8 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -1539,6 +1539,10 @@ void process_main(void)
/*
* Skeleton for receive statement:
*
+ * recv_mark L1 Optional
+ * call make_ref/monitor Optional
+ * ...
+ * recv_set L1 Optional
* L1: <-------------------+
* <-----------+ |
* | |
@@ -1557,6 +1561,34 @@ void process_main(void)
*
*/
+ OpCase(recv_mark_f): {
+ /*
+ * Save the current position in message buffer and the
+ * the label for the loop_rec/2 instruction for the
+ * the receive statement.
+ */
+ c_p->msg.mark = (BeamInstr *) Arg(0);
+ c_p->msg.saved_last = c_p->msg.last;
+ Next(1);
+ }
+
+ OpCase(i_recv_set): {
+ /*
+ * If the mark is valid (points to the loop_rec/2
+ * instruction that follows), we know that the saved
+ * position points to the first message that could
+ * possibly be matched out.
+ *
+ * If the mark is invalid, we do nothing, meaning that
+ * we will look through all messages in the message queue.
+ */
+ if (c_p->msg.mark == (BeamInstr *) (I+1)) {
+ c_p->msg.save = c_p->msg.saved_last;
+ }
+ I++;
+ /* Fall through to the loop_rec/2 instruction */
+ }
+
/*
* Pick up the next message and place it in x(0).
* If no message, jump to a wait or wait_timeout instruction.
diff --git a/erts/emulator/beam/erl_message.h b/erts/emulator/beam/erl_message.h
index 459c6363aa..489dee7b37 100644
--- a/erts/emulator/beam/erl_message.h
+++ b/erts/emulator/beam/erl_message.h
@@ -75,6 +75,13 @@ typedef struct {
ErlMessage** last; /* point to the last next pointer */
ErlMessage** save;
int len; /* queue length */
+
+ /*
+ * The following two fields are used by the recv_mark/1 and
+ * recv_set/1 instructions.
+ */
+ BeamInstr* mark; /* address to rec_loop/2 instruction */
+ ErlMessage** saved_last; /* saved last pointer */
} ErlMessageQueue;
#ifdef ERTS_SMP
@@ -137,6 +144,7 @@ do { \
(p)->msg.len--; \
if (__mp == NULL) \
(p)->msg.last = (p)->msg.save; \
+ (p)->msg.mark = 0; \
} while(0)
/* Reset message save point (after receive match) */
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index ef6062203e..49280a60e0 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -1425,5 +1425,8 @@ on_load
#
# R14A.
#
-recv_mark Lbl =>
-recv_set Lbl =>
+recv_mark f
+
+recv_set Fail | label Lbl | loop_rec Lf Reg => \
+ i_recv_set | label Lbl | loop_rec Lf Reg
+i_recv_set