[m-rev.] diff: improve PIC option handling

[Simon Taylor]

Estimated hours taken: 0.25
Branches: main

compiler/handle_options.m:
	Make `--mercury-linkage shared' imply `--pic-reg'.
	I don't think this actually fixes any bugs, because
	compile_target_code.m worked out whether `--pic-reg'
	was needed.

Index: handle_options.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/handle_options.m,v
retrieving revision 1.170
diff -u -u -r1.170 handle_options.m
--- handle_options.m	11 Feb 2003 04:32:46 -0000	1.170
+++ handle_options.m	12 Feb 2003 23:21:45 -0000
@@ -460,11 +460,28 @@
 		[]
 	),
 
+	%
+	% Set up options for position independent code.
+	%
+
+	% Shared libraries always use `--linkage shared'.
 	option_implies(compile_to_shared_lib, pic, bool(yes)),
-	option_implies(pic, pic_reg, bool(yes)),
 	option_implies(compile_to_shared_lib, linkage, string("shared")),
 	option_implies(compile_to_shared_lib, mercury_linkage,
 		string("shared")),
+
+	% On x86, using PIC takes a register away from us.
+	option_implies(pic, pic_reg, bool(yes)),
+
+	% If we're linking with shared Mercury libraries, we need
+	% to use the same calling convention as those libraries.
+	globals__io_lookup_string_option(mercury_linkage, MercuryLinkage),
+	( { MercuryLinkage = "shared" } ->
+		globals__io_set_option(pic_reg, bool(yes))
+	;
+		[]
+	),
+
 
 	% --high-level-code disables the use of low-level gcc extensions
 	option_implies(highlevel_code, gcc_non_local_gotos, bool(no)),
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