From 0772d1063c3e03cfb575fb5e948c120cfee14605 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Mon, 3 Sep 2012 12:08:40 +0200
Subject: Rewrite binary creation instructions to bs_init instructions

Rewrite the five binary creation instructions to a bs_init
instruction, in order to somewhat reduce code bloat.
---
 lib/compiler/src/beam_flatten.erl | 47 +++++++++++++--------------------------
 1 file changed, 16 insertions(+), 31 deletions(-)

(limited to 'lib/compiler/src/beam_flatten.erl')

diff --git a/lib/compiler/src/beam_flatten.erl b/lib/compiler/src/beam_flatten.erl
index 4cca406f45..04232d8fd2 100644
--- a/lib/compiler/src/beam_flatten.erl
+++ b/lib/compiler/src/beam_flatten.erl
@@ -79,43 +79,28 @@ norm_allocate({nozero,Ns,Nh,Inits}, Regs) ->
 
 %% insert_alloc_in_bs_init(ReverseInstructionStream, AllocationInfo) ->
 %%                                  impossible | ReverseInstructionStream'
-%%   A bs_init2/6 instruction should not be followed by a test heap instruction.
+%%   A bs_init/6 instruction should not be followed by a test heap instruction.
 %%   Given the AllocationInfo from a test heap instruction, merge the
-%%   allocation amounts into the previous bs_init2/6 instruction (if any).
+%%   allocation amounts into the previous bs_init/6 instruction (if any).
 %%
-insert_alloc_in_bs_init([I|_]=Is, Alloc) ->
-    case is_bs_constructor(I) of
-	false -> impossible;
-	true -> insert_alloc_1(Is, Alloc, [])
-    end.
-
-insert_alloc_1([{bs_init2=Op,Fail,Bs,Ws1,Regs,F,Dst}|Is], {_,nostack,Ws2,[]}, Acc) ->
-    Al = beam_utils:combine_heap_needs(Ws1, Ws2),
-    I = {Op,Fail,Bs,Al,Regs,F,Dst},
-    reverse(Acc, [I|Is]);
-insert_alloc_1([{bs_init_bits=Op,Fail,Bs,Ws1,Regs,F,Dst}|Is], {_,nostack,Ws2,[]}, Acc) ->
-    Al = beam_utils:combine_heap_needs(Ws1, Ws2),
-    I = {Op,Fail,Bs,Al,Regs,F,Dst},
-    reverse(Acc, [I|Is]);
-insert_alloc_1([{bs_append,Fail,Sz,Ws1,Regs,U,Bin,Fl,Dst}|Is],
-	       {_,nostack,Ws2,[]}, Acc) ->
+insert_alloc_in_bs_init([{bs_put,_,_,_}=I|Is], Alloc) ->
+    %% The instruction sequence ends with an bs_put/4 instruction.
+    %% We'll need to search backwards for the bs_init/6 instruction.
+    insert_alloc_1(Is, Alloc, [I]);
+insert_alloc_in_bs_init(_, _) -> impossible.
+
+insert_alloc_1([{bs_init=Op,Fail,Info0,Live,Ss,Dst}|Is],
+	       {_,nostack,Ws2,[]}, Acc) when is_integer(Live) ->
+    %% The number of extra heap words is always in the second position
+    %% in the Info tuple.
+    Ws1 = element(2, Info0),
     Al = beam_utils:combine_heap_needs(Ws1, Ws2),
-    I = {bs_append,Fail,Sz,Al,Regs,U,Bin,Fl,Dst},
+    Info = setelement(2, Info0, Al),
+    I = {Op,Fail,Info,Live,Ss,Dst},
     reverse(Acc, [I|Is]);
-insert_alloc_1([I|Is], Alloc, Acc) ->
+insert_alloc_1([{bs_put,_,_,_}=I|Is], Alloc, Acc) ->
     insert_alloc_1(Is, Alloc, [I|Acc]).
 
-
-%% is_bs_constructor(Instruction) -> true|false.
-%%  Test whether the instruction is a bit syntax construction
-%%  instruction that can occur at the end of a bit syntax
-%%  construction. (Since an empty binary would be expressed
-%%  as a literal, the bs_init2/6 instruction will not occur
-%%  at the end and therefore it is no need to test for it here.)
-%%
-is_bs_constructor({bs_put,_,_,_}) -> true;
-is_bs_constructor(_) -> false.
-
 %% opt(Is0) -> Is
 %%  Simple peep-hole optimization to move a {move,Any,{x,0}} past
 %%  any kill up to the next call instruction. (To give the loader
-- 
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