Support mergeable sections for fixed-size literals

On platforms that support them (ELF, macOS), use mergeable sections
(like `.rodata.cst8`) for 4-, 8- and 16-byte wide literals.

Works only if the LITERAL section is the default one.  If the user
provided their own LITERAL section, all literals are put in it
regardless of their sizes.

Support for mergeable string sections is introduced in this commit too
but needs further changes in C2C.ml .

1 files changed, 25 insertions, 32 deletions

diff --git a/aarch64/TargetPrinter.ml b/aarch64/TargetPrinter.ml
index a9d47bdd..ce6c51fc 100644
--- a/aarch64/TargetPrinter.ml
+++ b/aarch64/TargetPrinter.ml
@@ -165,8 +165,10 @@ module ELF_System : SYSTEM =
           variable_section ~sec:".data" ~bss:".bss" i
       | Section_const i | Section_small_const i ->
           variable_section ~sec:".section	.rodata" i
-      | Section_string       -> ".section	.rodata"
-      | Section_literal      -> ".section	.rodata"
+      | Section_string sz ->
+          elf_mergeable_string_section sz ".section	.rodata"
+      | Section_literal sz ->
+          elf_mergeable_literal_section sz ".section	.rodata"
       | Section_jumptable    -> ".section	.rodata"
       | Section_debug_info _ -> ".section	.debug_info,\"\",%progbits"
       | Section_debug_loc    -> ".section	.debug_loc,\"\",%progbits"
@@ -227,8 +229,10 @@ module MacOS_System : SYSTEM =
           variable_section ~sec:".data" i
       | Section_const i  | Section_small_const i ->
           variable_section ~sec:".const" ~reloc:".const_data" i
-      | Section_string -> ".const"
-      | Section_literal -> ".const"
+      | Section_string sz -> 
+          macos_mergeable_string_section sz
+      | Section_literal sz ->
+          macos_mergeable_literal_section sz
       | Section_jumptable -> ".text"
       | Section_user(s, wr, ex) ->
           sprintf ".section	\"%s\", %s, %s"
@@ -273,25 +277,21 @@ module Target(System: SYSTEM): TARGET =
 (* Associate labels to floating-point constants and to symbols. *)
 
     let emit_constants oc lit =
-      if exists_constants () then begin
-         section oc lit;
-         if Hashtbl.length literal64_labels > 0 then
-           begin
-             fprintf oc "	.balign 8\n";
-             Hashtbl.iter
-               (fun bf lbl -> fprintf oc "%a:	.quad	0x%Lx\n" label lbl bf)
-               literal64_labels
-           end;
-         if Hashtbl.length literal32_labels > 0 then
-           begin
-             fprintf oc "	.balign	4\n";
-             Hashtbl.iter
-               (fun bf lbl ->
-                  fprintf oc "%a:	.long	0x%lx\n" label lbl bf)
-               literal32_labels
-           end;
-         reset_literals ()
-      end
+      if Hashtbl.length literal64_labels > 0 then begin
+        section oc (Sections.with_size 8 lit);
+        fprintf oc "	.balign 8\n";
+        Hashtbl.iter
+          (fun bf lbl -> fprintf oc "%a:	.quad	0x%Lx\n" label lbl bf)
+          literal64_labels
+      end;
+      if Hashtbl.length literal32_labels > 0 then begin
+        section oc (Sections.with_size 4 lit);
+        fprintf oc "	.balign 4\n";
+        Hashtbl.iter
+          (fun bf lbl -> fprintf oc "%a:	.long	0x%lx\n" label lbl bf)
+          literal32_labels
+      end;
+      reset_literals ()
 
 (* Emit .file / .loc debugging directives *)
 
@@ -644,17 +644,10 @@ module Target(System: SYSTEM): TARGET =
              assert false
         end
 
-    let get_section_names name =
-      let (text, lit) =
-        match C2C.atom_sections name with
-        | t :: l :: _ -> (t, l)
-        | _    -> (Section_text, Section_literal) in
-      text,lit,Section_jumptable
-
     let print_align oc alignment =
       fprintf oc "	.balign %d\n" alignment
 
-    let print_jumptable oc jmptbl =
+    let print_jumptable oc _jmptbl =
       let print_tbl oc (lbl, tbl) =
         fprintf oc "%a:\n" label lbl;
         List.iter
@@ -663,7 +656,7 @@ module Target(System: SYSTEM): TARGET =
           tbl in
       if !jumptables <> [] then
         begin
-          section oc jmptbl;
+          section oc Section_jumptable;
           fprintf oc "	.balign 4\n";
           List.iter (print_tbl oc) !jumptables;
           jumptables := []