[patch][middle-end/PR102359]Not add initialization for DECL_VALUE_EXPR variables with -ftrivial-auto-var-init

[Qing Zhao <qing.zhao@oracle.com>]

Hi, 

This is the patch to fix this issue based on our discussion.

I have tested it on aarch64 with bootstrap and regtests. X86 bootstrap was done, regtests is ongoing.

Okay for trunk?

Thanks.

Qing

======================
From d349ef0145512efe7f9af2c6bbd01f636475bce3 Mon Sep 17 00:00:00 2001
From: qing zhao <qing.zhao@oracle.com>
Date: Mon, 4 Oct 2021 15:26:03 -0700
Subject: [PATCH] middle-end/102359 Not add initialization for variables that
 have been  initialized by FEs.

C++ FE creates proxy variables, which have associated DECL_VALUE_EXPR
and have been initialized by FE. For such auto variable, we should not
add initialization when -ftrivial-auto-var-init presents.

gcc/ChangeLog:

2021-10-04  qing zhao  <qing.zhao@oracle.com>

	* gimplify.c (is_decl_init_by_fe): New function.
	(gimplify_decl_expr): Not add initialization for an auto variable
	when it has been initialized by frontend.

gcc/testsuite/ChangeLog:

2021-10-04  qing zhao  <qing.zhao@oracle.com>

	* g++.dg/pr102359_1.C: New test.
	* g++.dg/pr102359_2.C: New test.
---
 gcc/gimplify.c                    | 21 ++++++++++++++++++++-
 gcc/testsuite/g++.dg/pr102359_1.C | 13 +++++++++++++
 gcc/testsuite/g++.dg/pr102359_2.C | 13 +++++++++++++
 3 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/pr102359_1.C
 create mode 100644 gcc/testsuite/g++.dg/pr102359_2.C

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index b27776a..d6865ad 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -1819,6 +1819,19 @@ gimple_add_padding_init_for_auto_var (tree decl, bool is_vla,
   gimplify_seq_add_stmt (seq_p, call);
 }
 
+/* Return true if the DECL is initialized by FE.
+   If the VAR_DECL has DECL_VALUE_EXPR that was created by FE (usually C++FE),
+   it's a proxy varaible, and FE already initializd the DECL_VALUE_EXPR of it.
+*/
+static bool
+is_decl_init_by_fe (tree decl, bool is_created_by_fe)
+{
+  if (DECL_HAS_VALUE_EXPR_P (decl)
+      && is_created_by_fe)
+    return true;
+  return false;
+}
+
 /* Return true if the DECL need to be automaticly initialized by the
    compiler.  */
 static bool
@@ -1871,8 +1884,13 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
   if (VAR_P (decl) && !DECL_EXTERNAL (decl))
     {
       tree init = DECL_INITIAL (decl);
+      bool is_value_expr_created_by_fe = false;
       bool is_vla = false;
 
+      /* Check whether a decl has FE created VALUE_EXPR here BEFORE 
+	 gimplify_vla_decl creates VALUE_EXPR for vla decl.  */
+      is_value_expr_created_by_fe = DECL_HAS_VALUE_EXPR_P (decl);
+
       poly_uint64 size;
       if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
 	  || (!TREE_STATIC (decl)
@@ -1934,7 +1952,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
       /* When there is no explicit initializer, if the user requested,
 	 We should insert an artifical initializer for this automatic
 	 variable.  */
-      else if (is_var_need_auto_init (decl))
+      else if (is_var_need_auto_init (decl)
+	       && !is_decl_init_by_fe (decl, is_value_expr_created_by_fe))
 	{
 	  gimple_add_init_for_auto_var (decl,
 					flag_auto_var_init,
diff --git a/gcc/testsuite/g++.dg/pr102359_1.C b/gcc/testsuite/g++.dg/pr102359_1.C
new file mode 100644
index 0000000..da643cd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr102359_1.C
@@ -0,0 +1,13 @@
+/* PR middle-end/102359 ICE gimplification failed since
+   r12-3433-ga25e0b5e6ac8a77a.  */
+/* { dg-do compile } */
+/* { dg-options "-ftrivial-auto-var-init=zero" } */
+/* { dg-require-effective-target c++17 } */
+
+struct A {
+  double a = 111;
+  auto foo() {
+    return [*this] { return a; };
+  }
+};
+int X = A{}.foo()();
diff --git a/gcc/testsuite/g++.dg/pr102359_2.C b/gcc/testsuite/g++.dg/pr102359_2.C
new file mode 100644
index 0000000..d026d72
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr102359_2.C
@@ -0,0 +1,13 @@
+/* PR middle-end/102359 ICE gimplification failed since
+   r12-3433-ga25e0b5e6ac8a77a.  */
+/* { dg-do run} */
+/* { dg-options "-ftrivial-auto-var-init=zero" } */
+/* { dg-require-effective-target c++17 } */
+
+int main()
+{
+ int i = 42;
+ auto l = [=]() mutable { return i; };
+ if (l() != i)
+   __builtin_abort ();
+}
-- 
1.9.1