[m-rev.] diff: fix bug with MLDS `base' optimization

[Fergus Henderson]

Branches: main
Estimated hours taken: 0.5

Fix a bug that broke the MLDS back-end in the case when either heap profiling
or accurate GC was enabled.

compiler/mlds_to_c.m:
	Fix a bug in Zoltan's recent change to declare a local variable
	"base" for initializing terms allocated on the heap:
	change the order in which code is output so that the
	declaration of "base" comes immediately after the "{",
	without any intervening code.  Otherwise, it is not legal C89.

Workspace: /home/ceres/fjh/mercury
Index: compiler/mlds_to_c.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/mlds_to_c.m,v
retrieving revision 1.154
diff -u -d -r1.154 mlds_to_c.m
--- compiler/mlds_to_c.m	11 Nov 2003 03:19:46 -0000	1.154
+++ compiler/mlds_to_c.m	12 Nov 2003 06:52:17 -0000
@@ -2808,6 +2808,28 @@
 	mlds_indent(Indent),
 	io__write_string("{\n"),
 
+	% When filling in the fields of a newly allocated cell, use a fresh
+	% local variable as the base address for the field references in
+	% preference to an lval that is more expensive to access. This yields
+	% a speedup of about 0.3%.
+
+	( { Target = var(_, _) } ->
+		{ Base = lval(Target) }
+	;
+		% It doesn't matter what string we pick for BaseVarName,
+		% as long as its declaration doesn't hide any of the variables
+		% inside Args. This is not hard to ensure, since the printed
+		% forms of the variables inside Args all include "__".
+		{ BaseVarName = "base" },
+		{ Base = string(BaseVarName) },
+		mlds_indent(Context, Indent + 1),
+		mlds_output_type_prefix(Type),
+		io__write_string(" "),
+		io__write_string(BaseVarName),
+		mlds_output_type_suffix(Type),
+		io__write_string(";\n")
+	),
+
 	% for --gc accurate, we need to insert a call to GC_check()
 	% before every allocation
 	globals__io_get_gc_method(GC_Method),
@@ -2838,27 +2860,6 @@
 	mlds_maybe_output_heap_profile_instr(Context, Indent + 1, Args,
 		FuncName, MaybeCtorName),
 
-	% When filling in the fields of a newly allocated cell, use a fresh
-	% local variable as the base address for the field references in
-	% preference to an lval that is more expensive to access. This yields
-	% a speedup of about 0.3%.
-
-	( { Target = var(_, _) } ->
-		{ Base = lval(Target) }
-	;
-		% It doesn't matter what string we pick for BaseVarName,
-		% as long as its declaration doesn't hide any of the variables
-		% inside Args. This is not hard to ensure, since the printed
-		% forms of the variables inside Args all include "__".
-		{ BaseVarName = "base" },
-		{ Base = string(BaseVarName) },
-		mlds_indent(Context, Indent + 1),
-		mlds_output_type_prefix(Type),
-		io__write_string(" "),
-		io__write_string(BaseVarName),
-		mlds_output_type_suffix(Type),
-		io__write_string(";\n")
-	),
 	mlds_indent(Context, Indent + 1),
 	write_lval_or_string(Base),
 	io__write_string(" = "),

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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