Add simpler alternative to generate gimple

Author: GuillaumeGomez

doc/gimple.md

@@ -36,7 +36,7 @@ int main() {
     // To set `-O3`, update it depending on your needs.
     gcc_jit_context_set_int_option(ctxt, GCC_JIT_INT_OPTION_OPTIMIZATION_LEVEL, 3);
     // Very important option to generate the gimple format.
-    gcc_jit_context_add_command_line_option(ctxt, "-fdump-tree-gimple");
+    gcc_jit_context_set_bool_option(ctxt, GCC_JIT_BOOL_OPTION_DUMP_INITIAL_GIMPLE, 1);
     create_code(ctxt, NULL);
 
     gcc_jit_context_compile(ctxt);
@@ -54,21 +54,13 @@ Then we can compile it by using:
 gcc local.c -I `pwd`/gcc/gcc/jit/ -L `pwd`/gcc-build/gcc -lgccjit -o out
 ```
 
-Before running it, I recommend running:
-
-```console
-rm -rf /tmp/libgccjit-*
-```
-
-to make it easier for you to know which folder to look into.
-
 And finally when you run it:
 
 ```console
 LD_LIBRARY_PATH=`pwd`/gcc-build/gcc LIBRARY_PATH=`pwd`/gcc-build/gcc ./out
 ```
 
-You should now have a file named with path looking like `/tmp/libgccjit-9OFqkD/fake.c.006t.gimple` which contains:
+It should display:
 
 ```c
 __attribute__((const))
@@ -95,3 +87,25 @@ int xxx ()
   return D.3394;
 }
 ```
+
+An alternative way to generate the GIMPLE is to replace:
+
+```c
+    gcc_jit_context_set_bool_option(ctxt, GCC_JIT_BOOL_OPTION_DUMP_INITIAL_GIMPLE, 1);
+```
+
+with:
+
+```c
+    gcc_jit_context_add_command_line_option(ctxt, "-fdump-tree-gimple");
+```
+
+(although you can have both at the same time too). Then you can compile it like previously. Only one difference: before executing it, I recommend to run:
+
+```console
+rm -rf /tmp/libgccjit-*
+```
+
+to make it easier for you to know which folder to look into.
+
+Once the execution is done, you should now have a file with path looking like `/tmp/libgccjit-9OFqkD/fake.c.006t.gimple` which contains the GIMPLE format.