File 2153-Simplify-the-raise-instruction-to-reduce-code-size.patch of Package erlang
From 3c0f98c1b0e74eb58a4e4e82a3ec89dc7ecdb579 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Thu, 7 Apr 2016 10:06:44 +0200
Subject: [PATCH 1/2] Simplify the raise instruction to reduce code size
The raise/2 instruction is almost always used like this:
raise x(2) x(1)
Therefore, we can translate it to an internal i_raise/0
instruction that uses x(2) x(1) as its implicit operands.
We will also remove the backward compatibility with R10-0. It is
unlikely that anyone still is using BEAM files compiled with the R10-0
compiler, especially since most of those modules cannot be loaded. The
loader will refuse to load any module that uses the old non-GCIng
arithmetic instructions or the non-GCing versions of length/1 or
size/1.
Doing these changes will reduce both the size of the loaded BEAM
code and size of the code in process_main().
---
erts/emulator/beam/beam_emu.c | 54 ++++++++++---------------------------------
erts/emulator/beam/ops.tab | 9 +++++++-
2 files changed, 20 insertions(+), 43 deletions(-)
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 09a41f2..d648a2f 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -3360,48 +3360,18 @@ do { \
goto do_schedule;
}
- OpCase(raise_ss): {
- /* This was not done very well in R10-0; then, we passed the tag in
- the first argument and hoped that the existing c_p->ftrace was
- still correct. But the ftrace-object already includes the tag
- (or rather, the freason). Now, we pass the original ftrace in
- the first argument. We also handle atom tags in the first
- argument for backwards compatibility.
- */
- Eterm raise_val1;
- Eterm raise_val2;
- GetArg2(0, raise_val1, raise_val2);
- c_p->fvalue = raise_val2;
- if (c_p->freason == EXC_NULL) {
- /* a safety check for the R10-0 case; should not happen */
- c_p->ftrace = NIL;
- c_p->freason = EXC_ERROR;
- }
- /* for R10-0 code, keep existing c_p->ftrace and hope it's correct */
- switch (raise_val1) {
- case am_throw:
- c_p->freason = EXC_THROWN & ~EXF_SAVETRACE;
- break;
- case am_error:
- c_p->freason = EXC_ERROR & ~EXF_SAVETRACE;
- break;
- case am_exit:
- c_p->freason = EXC_EXIT & ~EXF_SAVETRACE;
- break;
- default:
- {/* R10-1 and later
- XXX note: should do sanity check on given trace if it can be
- passed from a user! Currently only expecting generated calls.
- */
- struct StackTrace *s;
- c_p->ftrace = raise_val1;
- s = get_trace_from_exc(raise_val1);
- if (s == NULL) {
- c_p->freason = EXC_ERROR;
- } else {
- c_p->freason = PRIMARY_EXCEPTION(s->freason);
- }
- }
+ OpCase(i_raise): {
+ Eterm raise_trace = x(2);
+ Eterm raise_value = x(1);
+ struct StackTrace *s;
+
+ c_p->fvalue = raise_value;
+ c_p->ftrace = raise_trace;
+ s = get_trace_from_exc(raise_trace);
+ if (s == NULL) {
+ c_p->freason = EXC_ERROR;
+ } else {
+ c_p->freason = PRIMARY_EXCEPTION(s->freason);
}
goto find_func_info;
}
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 15f2783..96a3a72 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -251,7 +251,14 @@ case_end x
badmatch x
if_end
-raise s s
+
+# Operands for raise/2 are almost always in x(2) and x(1).
+# Optimize for that case.
+raise x==2 x==1 => i_raise
+raise Trace=y Value=y => move Trace x=2 | move Value x=1 | i_raise
+raise Trace Value => move Trace x=3 | move Value x=1 | move x=3 x=2 | i_raise
+
+i_raise
# Internal now, but could be useful to make known to the compiler.
badarg j
--
2.1.4
