From: Alexandre Oliva <aoliva@redhat.com>
Date: Thu, 21 Dec 2017 18:14:06 +0000 (+0000)
Subject: [SFN] propagate single-nondebug-stmt's side effects to enclosing list
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=cb6332333854a698cbfc2ea4b1e52ce9bd59f664;p=gcc.git

[SFN] propagate single-nondebug-stmt's side effects to enclosing list

Statements without side effects, preceded by debug begin stmt markers,
would become a statement list with side effects, although the stmt on
its own would be extracted from the list and remain not having side
effects.  This causes debug info and possibly codegen differences.
This patch fixes it, identifying the situation in which the stmt would
have been extracted from the stmt list, and propagating the side
effects flag from the stmt to the list.

for  gcc/ChangeLog

	PR debug/83419
	* c-family/c-semantics.c (pop_stmt_list): Propagate side
	effects from single nondebug stmt to container list.

for  gcc/testsuite/ChangeLog

	PR debug/83419
	* gcc.dg/pr83419.c: New.

From-SVN: r255947
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d3c4063a5ce..2851eb67cc4 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2017-12-21  Alexandre Oliva <aoliva@redhat.com>
+
+	PR debug/83419
+	* c-family/c-semantics.c (pop_stmt_list): Propagate side
+	effects from single nondebug stmt to container list.
+
 2017-12-21  James Greenhalgh  <james.greenhalgh@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_expand_vector_init): Modify code
diff --git a/gcc/c-family/c-semantics.c b/gcc/c-family/c-semantics.c
index cd872d8ac74..3a972c32c8e 100644
--- a/gcc/c-family/c-semantics.c
+++ b/gcc/c-family/c-semantics.c
@@ -96,6 +96,15 @@ pop_stmt_list (tree t)
 	      t = l;
 	      tsi_link_before (&i, u, TSI_SAME_STMT);
 	    }
+	  while (!tsi_end_p (i)
+		 && TREE_CODE (tsi_stmt (i)) == DEBUG_BEGIN_STMT)
+	    tsi_next (&i);
+	  /* If there's only one nondebug stmt in the list, we'd have
+	     extracted the stmt and dropped the list, and we'd take
+	     TREE_SIDE_EFFECTS from that statement, so keep the list's
+	     TREE_SIDE_EFFECTS in sync.  */
+	  if (tsi_one_before_end_p (i))
+	    TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (tsi_stmt (i));
 	}
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7171973d969..8cc163adac0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-12-21  Alexandre Oliva <aoliva@redhat.com>
+
+	PR debug/83419
+	* gcc.dg/pr83419.c: New.
+
 2017-12-21  James Greenhalgh  <james.greenhalgh@arm.com>
 
 	* gcc.target/aarch64/vect-slp-dup.c: New.
diff --git a/gcc/testsuite/gcc.dg/pr83419.c b/gcc/testsuite/gcc.dg/pr83419.c
new file mode 100644
index 00000000000..3d4f1d27701
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr83419.c
@@ -0,0 +1,16 @@
+/* PR debug/83419 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fcompare-debug" } */
+
+int a, b;
+void foo (int, ...);
+
+void
+bar (void)
+{
+  if (a || 1 == b)
+    foo (1);
+  else
+    0;
+  foo (1, 0);
+}