[OCaml] Fix incorrect use of CAMLlocal in nested blocks

[jberdine]

Summary

The OCaml manual states:

Local variables of type value must be declared with one of the
CAMLlocal macros. [...] These macros must be used at the beginning
of the function, not in a nested block.

This patch moves several instances of CAMLlocal macros from nested
blocks to the function beginning.

[jberdine]

@whitequark, could I bother you to commit this for me?

[CodaFi]

Apologies for not bringing this up in the earlier patch, but is there a reason this isn't using/building on the existing DI C bindings we have?

[whitequark]

@CodaFi Did you mean to commentn on D52210? I'm confused here...

bindings/ocaml/llvm/llvm_ocaml.c

LLVMStructSetBody(Ty, (LLVMTypeRef *) ElementTypes,
                     Wosize_val(ElementTypes), Bool_val(Packed));
   return Val_unit;
 }
 
 /* lltype -> string option */
 CAMLprim value llvm_struct_name(LLVMTypeRef Ty)
 {
   CAMLparam0();
+  CAMLlocal1(result);
   const char *C = LLVMGetStructName(Ty);
   if (C) {
-    CAMLlocal1(result);
     result = caml_alloc_small(1, 0);
     Store_field(result, 0, caml_copy_string(C));
     CAMLreturn(result);
   }
   CAMLreturn(Val_int(0));
 }
 
 /* lltype -> lltype array */

 };
 
 /* llvalue -> ValueKind.t */
 #define DEFINE_CASE(Val, Kind) \
     do {if (LLVMIsA##Kind(Val)) CAMLreturn(Val_int(Kind));} while(0)
 
 CAMLprim value llvm_classify_value(LLVMValueRef Val) {
   CAMLparam0();
+  CAMLlocal1(result);
   if (!Val)
     CAMLreturn(Val_int(NullValue));
   if (LLVMIsAConstant(Val)) {
     DEFINE_CASE(Val, BlockAddress);
     DEFINE_CASE(Val, ConstantAggregateZero);
     DEFINE_CASE(Val, ConstantArray);
     DEFINE_CASE(Val, ConstantDataArray);
     DEFINE_CASE(Val, ConstantDataVector);
     DEFINE_CASE(Val, ConstantExpr);
     DEFINE_CASE(Val, ConstantFP);
     DEFINE_CASE(Val, ConstantInt);
     DEFINE_CASE(Val, ConstantPointerNull);
     DEFINE_CASE(Val, ConstantStruct);
     DEFINE_CASE(Val, ConstantVector);
   }
   if (LLVMIsAInstruction(Val)) {
-    CAMLlocal1(result);
     result = caml_alloc_small(1, 0);
     Store_field(result, 0, Val_int(LLVMGetInstructionOpcode(Val)));
     CAMLreturn(result);
   }
   if (LLVMIsAGlobalValue(Val)) {
     DEFINE_CASE(Val, Function);
     DEFINE_CASE(Val, GlobalAlias);
     DEFINE_CASE(Val, GlobalIFunc);

 /* llcontext -> llvalue */
 CAMLprim LLVMValueRef llvm_mdnull(LLVMContextRef C) {
   return NULL;
 }
 
 /* llvalue -> string option */
 CAMLprim value llvm_get_mdstring(LLVMValueRef V) {
   CAMLparam0();
+  CAMLlocal2(Option, Str);
   const char *S;
   unsigned Len;
 
   if ((S = LLVMGetMDString(V, &Len))) {
-    CAMLlocal2(Option, Str);
-
     Str = caml_alloc_string(Len);
     memcpy(String_val(Str), S, Len);
     Option = alloc(1,0);
     Store_field(Option, 0, Str);
     CAMLreturn(Option);
   }
   CAMLreturn(Val_int(0));
 }