bugfix: De-duplicate consecutive ARM32 label

Fixes #6

Author: jonahbeckford

CHANGES.md

@@ -7,6 +7,7 @@
   `flexdll/flexdll.c`, etc. to make robust to the lack of `flexdll/.git`.
    Vendor supplied patches are used by DkSDK CMake's `110-ocaml-lang`.
 * Supply `DKML_HOST_ABI` to post-transform configure scripts.
+* bugfix: De-duplicate consecutive ARM32 label. <https://github.com/diskuv/dkml-compiler/issues/6>
 
 ## 2.1.3
 

src/p/ocaml-common-4_14-a07-arm32dedup.md

@@ -0,0 +1,70 @@
+# arm32 deduplicate labels
+
+Problem that only appears on clang (not former GNU AS used before Android NDK 24):
+
+```text
+make: Entering directory '/workspaces/dkml-compiler/dist-android_arm32v7a-on-linux_x86/opt/mlcross/android_arm32v7a/src/ocaml/stdlib'
+/usr/bin/env /workspaces/dkml-compiler/dist-android_arm32v7a-on-linux_x86/opt/mlcross/android_arm32v7a/src/ocaml/support/ocamloptTarget.wrapper -strict-sequence -absname -w +a-4-9-41-42-44-45-48-70 -g -warn-error +A -bin-annot -nostdlib -principal -safe-string -strict-formats -dstartup -S  -nopervasives -c camlinternalAtomic.ml
+camlinternalAtomic.s:94:1: error: symbol '.L100' is already defined
+.L100:
+^
+camlinternalAtomic.s:146:1: error: symbol '.L105' is already defined
+.L105:
+^
+camlinternalAtomic.s:173:1: error: symbol '.L106' is already defined
+.L106:
+^
+camlinternalAtomic.s:202:1: error: symbol '.L108' is already defined
+.L108:
+^
+camlinternalAtomic.s:262:1: error: symbol '.L110' is already defined
+.L110:
+^
+camlinternalAtomic.s:289:1: error: symbol '.L112' is already defined
+.L112:
+^
+File "/workspaces/dkml-compiler/dist-android_arm32v7a-on-linux_x86/opt/mlcross/android_arm32v7a/src/ocaml/stdlib/camlinternalAtomic.ml", line 1:
+Error: Assembler error, input left in file /workspaces/dkml-compiler/dist-android_arm32v7a-on-linux_x86/opt/mlcross/android_arm32v7a/src/ocaml/stdlib/camlinternalAtomic.s
+make: *** [Makefile:231: camlinternalAtomic.cmx] Error 2
+make: Leaving directory '/workspaces/dkml-compiler/dist-android_arm32v7a-on-linux_x86/opt/mlcross/android_arm32v7a/src/ocaml/stdlib'
+```
+
+Here is the definition of a function:
+
+```armasm
+# lines 1 - 82
+camlCamlinternalAtomic__make_9: # line 83
+	.file	2	"camlinternalAtomic.ml"
+	.loc	2	27
+	.cfi_startproc
+	.loc	2	27
+	sub	sp, sp, #0x8 #  Beginning of [Lprologue]
+	.cfi_adjust_cfa_offset	8
+	.cfi_offset 14, -4
+	str	lr, [sp, #4]
+.L100: # line 92        
+	.loc	2	27   #  End of [Lprologue]
+.L100: # line 94.       Beginning and end of [Llabel]
+	.loc	2	27
+   sub     alloc_ptr, alloc_ptr, #0x8
+	ldr	r1, [domain_state_ptr, 0]
+     cmp     alloc_ptr, r1
+     bcc     .L102
+.L103:     add     r1, alloc_ptr, #4
+	ldr	lr, [sp, #4]
+	movs	r2, #0x400
+	str	r2, [r1, #-4]
+	str	r0, [r1, #0]
+	mov	r0, r1
+	add	sp, sp, #0x8
+	.cfi_adjust_cfa_offset	-8
+	bx	lr
+	.cfi_adjust_cfa_offset	8
+.L102:	bl	caml_call_gc(PLT)
+.L101:	b	.L103
+	.cfi_endproc
+	.type	camlCamlinternalAtomic__make_9, %function
+	.size	camlCamlinternalAtomic__make_9, .-camlCamlinternalAtomic__make_9
+```
+
+This patch gets rid of any duplicate, consecutive labels.

src/p/ocaml-common-4_14-a07-arm32dedup.patch

@@ -0,0 +1,41 @@
+diff --git a/asmcomp/arm/emit.mlp b/asmcomp/arm/emit.mlp
+index a8285d7363..16645da96e 100644
+--- a/asmcomp/arm/emit.mlp
++++ b/asmcomp/arm/emit.mlp
+@@ -884,10 +884,17 @@ let max_instruction_size i =
+ 
+ (* Emission of an instruction sequence *)
+ 
+-let rec emit_all env ninstr fallthrough i =
++let rec emit_all env ninstr fallthrough prev_desc i =
+   (* ninstr = number of 32-bit code words emitted since last constant island *)
+   (* fallthrough is true if previous instruction can fall through *)
+   if i.desc = Lend then () else begin
++  match prev_desc, i.desc with
++  | Some Lprologue, Llabel lbl when env.f.fun_tailrec_entry_point_label=lbl ->
++    (* Skip duplicate, consecutive labels which cause
++       > error: symbol '.L100' is already defined
++       with clang (ex. Android NDK 24+) but not with GNU AS. *)
++    emit_all env ninstr (has_fallthrough i.desc) (Some i.desc) i.next
++  | _ ->
+     (* Make sure literals not yet emitted remain addressable,
+        or emit them in a new constant island. *)
+     (* fldd can address up to +/-1KB, ldr can address up to +/-4KB *)
+@@ -908,7 +915,7 @@ let rec emit_all env ninstr fallthrough i =
+       end else
+         ninstr in
+     let n = emit_instr env i in
+-    emit_all env (ninstr' + n) (has_fallthrough i.desc) i.next
++    emit_all env (ninstr' + n) (has_fallthrough i.desc) (Some i.desc) i.next
+   end
+ 
+ (* Emission of a function declaration *)
+@@ -926,7 +933,7 @@ let fundecl fundecl =
+   `{emit_symbol fundecl.fun_name}:\n`;
+   emit_debug_info fundecl.fun_dbg;
+   cfi_startproc();
+-  emit_all env 0 true fundecl.fun_body;
++  emit_all env 0 true None fundecl.fun_body;
+   emit_literals env;
+   List.iter emit_call_gc env.call_gc_sites;
+   List.iter emit_call_bound_error env.bound_error_sites;