Fix unwind information and implement _exception_code and _exception_info intrinsics. wasm3 now compiles.

Author: Pascal Beyer

examples/wasm3.bat

@@ -0,0 +1,12 @@
+
+git clone https://github.com/wasm3/wasm3.git --recursive --depth 1 --branch v0.5.0
+cd wasm3 || exit /b 1
+
+git clean -xdf
+
+cmake -B build -G Ninja -D CMAKE_C_COMPILER="%~dp0..\hlc.exe" || exit /b 1
+cd build || exit /b 1
+
+ninja || exit /b 1
+
+cd ..\..

src/emit_x64.c

@@ -2413,8 +2413,12 @@ func struct emit_location *emit_intrinsic(struct context *context, struct ast_fu
         emit(0xcc);
         return emit_location_invalid(context);
     }else if(string_match(identifier, string("_AddressOfReturnAddress"))){
-        struct emit_location *return_address = emit_location_stack_relative(context, -(8 + 8 * /*amount_of_saved_registers*/2), /*size*/8);
+        struct emit_location *return_address = emit_location_stack_relative(context, -(8 * (s32)__popcnt(context->current_function->pushed_register_mask)), /*size*/8);
         return emit_load_address(context, return_address, allocate_register(context, REGISTER_KIND_gpr));
+    }else if(string_match(identifier, string("_exception_info"))){
+        return emit_location_loaded(context, REGISTER_KIND_gpr, REGISTER_R13, 8);
+    }else if(string_match(identifier, string("_exception_code"))){
+        return emit_location_loaded(context, REGISTER_KIND_gpr, REGISTER_R12, 4);
     }else{
         invalid_code_path;
     }
@@ -4755,15 +4759,31 @@ func void emit_code_for_function(struct context *context, struct ast_function *f
     //           maybe the large struct code should live in the epilog?
     // @incomplete: we do not honor the calling convention here...
     // @WARNING: If you change this code you have to also change the implementation of `_AddressOfReturnAddress`.
-    s32 amount_of_saved_registers = 2;
+    
+    if(function->type->flags & FUNCTION_TYPE_FLAGS_is_seh_filter){
+        emit(0x41); emit(0x55); // push r13
+        emit(0x41); emit(0x54); // push r12
+        function->pushed_register_mask |= (1 << REGISTER_R12) | (1 << REGISTER_R13);
+    }
+    
     emit(PUSH_REGISTER_DI);
     emit(PUSH_REGISTER_SI);
+    emit(PUSH_REGISTER_BP);
 
-    function->pushed_register_mask = (1 << REGISTER_SI) | (1 << REGISTER_DI) | (1 << REGISTER_BP);
+    function->pushed_register_mask |= (1 << REGISTER_SI) | (1 << REGISTER_DI) | (1 << REGISTER_BP);
 
-    emit(PUSH_REGISTER_BP);
+    s32 amount_of_saved_registers = __popcnt(function->pushed_register_mask) - /*rbp*/1;
     emit_reg_reg__(context, REXW, MOVE_REG_REGM, REGISTER_BP, REGISTER_SP);
 
+    if(function->type->flags & FUNCTION_TYPE_FLAGS_is_seh_filter){
+        // mov r13, rdx
+        // mov r12, [rdx]
+        // mov r12d, [r12]
+        emit(0x49); emit(0x89); emit(0xcd);
+        emit(0x4c); emit(0x8b); emit(0x21);
+        emit(0x45); emit(0x8b); emit(0x24); emit(0x24);
+    }
+    
     {
         // at this point we have pushed rbp so the memory layout is as follows:
         //    | memory for the function | old rbp | saved non-volitiles | ret ptr | arg0 | arg1 | arg2 | ...
@@ -4921,6 +4941,11 @@ func void emit_code_for_function(struct context *context, struct ast_function *f
     emit(POP_REGISTER_SI);
     emit(POP_REGISTER_DI);
 
+    if(function->type->flags & FUNCTION_TYPE_FLAGS_is_seh_filter){
+        emit(0x41); emit(0x5c); // push r12
+        emit(0x41); emit(0x5d); // push r13
+    }
+    
     emit(NEAR_RET_INSTRUCTION);
 
     if(context->alloca_patch_nodes.first){

src/obj_writer.c

@@ -862,19 +862,25 @@ func void *push_unwind_information_for_function(struct memory_arena *arena, stru
         *push_struct(arena, u32) = (u32)stack_space_needed;
     }
 
-    u8 amount_of_pushed_registers = (u8)__popcnt(function->pushed_register_mask);
+    // @incomplete: Pushing r8-r15 needs 2 bytes each.
+    u8 big_pushes   = (u8)__popcnt((function->pushed_register_mask >> 8) & 0xff);
+    u8 small_pushes = (u8)__popcnt((function->pushed_register_mask >> 0) & 0xff);
+    
+    u8 push_offset_in_prolog = 2 * big_pushes + small_pushes;
 
     struct unwind_code *frame_pointer_code = push_struct(arena, struct unwind_code);
-    frame_pointer_code->offset_in_prolog = (u8)(amount_of_pushed_registers + /*mov rbp, rsp*/3);
+    frame_pointer_code->offset_in_prolog = (u8)(push_offset_in_prolog + /*mov rbp, rsp*/3);
     frame_pointer_code->operation_code   = /*UWOP_SET_FPREG*/3;
 
-    for(u8 register_index = 0, offset_in_prolog = amount_of_pushed_registers; register_index < 16; register_index++){
+    for(u8 register_index = 0, offset_in_prolog = push_offset_in_prolog; register_index < 16; register_index++){
         if(!(function->pushed_register_mask & (1u << register_index))) continue;
 
         struct unwind_code *pushed_register_code = push_struct(arena, struct unwind_code);
-        pushed_register_code->offset_in_prolog = offset_in_prolog--;
+        pushed_register_code->offset_in_prolog = offset_in_prolog;
         pushed_register_code->operation_code = /*UWOP_PUSH_NONVOL*/0;
         pushed_register_code->operation_info = register_index;
+        
+        offset_in_prolog -= 1 + (register_index >= 8);
     }
 
     unwind_info->count_of_codes = (u8)((struct unwind_code *)arena_current(arena) - unwind_info->codes);