Struct declaration and initialization in TREES

[Erick Ochoa <erick dot ochoa at theobroma-systems dot com>]

Hi,

I'm interested in printing VAR_DECL trees that are of type
RECORD_TYPE. I am using the function print_generic_decl
for debugging and found this interesting behaviour.

When I do initialization of structs using the following
syntax:

```
struct aStruct { _Bool e; int a; char b; float c; double d; _Bool f; long h;};
struct aStruct astruct = { .e = 0, .a = 1, .b = 2, .c = 3.0, .d = 4.0, .f = 5, .h = 6 };
```

print_generic_decl will print the following output:

```
INTERESTED IN:   static struct aStruct astruct = <<< error >>>;
```

Am I using the correct API? Is this a limitation of the API?
Would people be interested in me extending this API to print
out something more useful? I already have some code that
iterates over fields and prints out names and types. It
can still use some work though.

However, I understand if this is the intended behaviour.
Another question (related to the possibility of intended behaviour)
is: how is struct initialization represented in trees?
(I.e. will each field be initialized separately or something else
happens?)

Thanks! I also include the patch in case people want a simple
working example on how to print declarations.

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 6b857bd..f4f1376 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1368,6 +1368,7 @@ OBJS = \
 	incpath.o \
 	init-regs.o \
 	internal-fn.o \
+	ipa-hello-world.o \
 	ipa-cp.o \
 	ipa-sra.o \
 	ipa-devirt.o \
diff --git a/gcc/common.opt b/gcc/common.opt
index b4dc31c..304ec9f 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -3348,4 +3348,7 @@ fipa-ra
 Common Report Var(flag_ipa_ra) Optimization
 Use caller save register across calls if possible.
 
+fipa-typelist
+Common Report Var(flag_ipa_typelist) TBD
+
 ; This comment is to ensure we retain the blank line above.
diff --git a/gcc/ipa-hello-world.c b/gcc/ipa-hello-world.c
new file mode 100644
index 0000000..ed4ae11
--- /dev/null
+++ b/gcc/ipa-hello-world.c
@@ -0,0 +1,78 @@
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "backend.h"
+#include "tree.h"
+#include "gimple-expr.h"
+#include "predict.h"
+#include "alloc-pool.h"
+#include "tree-pass.h"
+#include "cgraph.h"
+#include "diagnostic.h"
+#include "fold-const.h"
+#include "gimple-fold.h"
+#include "symbol-summary.h"
+#include "tree-vrp.h"
+#include "ipa-prop.h"
+#include "tree-pretty-print.h"
+#include "tree-inline.h"
+#include "ipa-fnsummary.h"
+#include "ipa-utils.h"
+#include "tree-ssa-ccp.h"
+#include "stringpool.h"
+#include "attribs.h"
+
+
+static unsigned int
+iphw_execute()
+{
+  if (!dump_file) return 0;
+  varpool_node *node;
+  FOR_EACH_VARIABLE(node)
+  {
+    gcc_assert(node->decl);
+    tree decl = node->decl;
+    gcc_assert(TREE_CODE(decl) == VAR_DECL);
+
+    tree curr_type = TREE_TYPE(decl);
+    gcc_assert(curr_type);
+
+    const bool is_struct = TREE_CODE(curr_type) == RECORD_TYPE;
+    if (is_struct) fprintf(dump_file, "INTERESTED IN: ");
+    print_generic_decl(dump_file, decl, TDF_DETAILS);
+    fprintf(dump_file, "\n");
+  }
+  return 0;
+}
+
+namespace {
+const pass_data pass_data_ipa_hello_world =
+{
+  SIMPLE_IPA_PASS,
+  "hello_world",
+  OPTGROUP_NONE,
+  TV_NONE,
+  (PROP_cfg | PROP_ssa),
+  0,
+  0,
+  0,
+  0,
+};
+
+class pass_ipa_hello_world : public simple_ipa_opt_pass
+{
+public:
+  pass_ipa_hello_world (gcc::context *ctx)
+    : simple_ipa_opt_pass(pass_data_ipa_hello_world, ctx)
+  {}
+
+  virtual bool gate(function*) { return flag_ipa_typelist; }
+  virtual unsigned execute (function*) { return iphw_execute(); }
+};
+} // anon namespace
+
+simple_ipa_opt_pass*
+make_pass_ipa_hello_world (gcc::context *ctx)
+{
+  return new pass_ipa_hello_world (ctx);
+}
diff --git a/gcc/passes.def b/gcc/passes.def
index 798a391..52cd14b 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -146,6 +146,7 @@ along with GCC; see the file COPYING3.  If not see
   NEXT_PASS (pass_ipa_profile);
   NEXT_PASS (pass_ipa_icf);
   NEXT_PASS (pass_ipa_devirt);
+  NEXT_PASS (pass_ipa_hello_world);
   NEXT_PASS (pass_ipa_cp);
   NEXT_PASS (pass_ipa_sra);
   NEXT_PASS (pass_ipa_cdtor_merge);
diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
index a987661..915fc69 100644
--- a/gcc/tree-pass.h
+++ b/gcc/tree-pass.h
@@ -498,6 +498,7 @@ extern ipa_opt_pass_d *make_pass_ipa_fn_summary (gcc::context *ctxt);
 extern ipa_opt_pass_d *make_pass_ipa_inline (gcc::context *ctxt);
 extern simple_ipa_opt_pass *make_pass_ipa_free_lang_data (gcc::context *ctxt);
 extern simple_ipa_opt_pass *make_pass_ipa_free_fn_summary (gcc::context *ctxt);
+extern simple_ipa_opt_pass *make_pass_ipa_hello_world (gcc::context *ctxt);
 extern ipa_opt_pass_d *make_pass_ipa_cp (gcc::context *ctxt);
 extern ipa_opt_pass_d *make_pass_ipa_sra (gcc::context *ctxt);
 extern ipa_opt_pass_d *make_pass_ipa_icf (gcc::context *ctxt);