Add note about the DUMP environemnt variable

README.md

@@ -83,3 +83,14 @@ Build and run time dependencies:
 Run time dependencies:
 
  - [`nasm`](https://www.nasm.us/), for assembling support (i.e. not `-S`)
+
+
+## Insight
+
+The compiler stays mostly silent. To get more insight into the passes that
+constitute it, set the `DUMP` environment variable, which will print functions
+after each pass. For example:
+
+```
+DUMP=1 build/tcg tests/in/critical_edge.tc
+```

src/backend/inst.c

@@ -70,7 +70,6 @@ print_mfunction(FILE *f, MFunction *mfunction)
 	}
 }
 
-
 void
 dump_mfunction_after_pass(MFunction *mfunction, const char *pass_name)
 {

src/main.c

@@ -96,6 +96,13 @@ parse_source(ErrorContext *ec, Arena *arena, Str source)
 		arena_restore(arena, arena_start);
 		longjmp(ec->loc, 1);
 	}
+
+	if (DUMP) {
+		fprintf(stderr, "After parsing:\n");
+		print_module(stderr, module);
+		fprintf(stderr, "\n\n");
+	}
+
 	return module;
 }
 

src/middleend/ir.c

@@ -430,7 +430,6 @@ print_function(FILE *f, Function *function)
 		}
 	}
 	validate_function(function);
-	fprintf(f, "\n\n");
 }
 
 bool