From: Jakub Jelinek <jakub@redhat.com>
Date: Mon, 25 Jun 2018 17:32:55 +0000 (+0200)
Subject: backport: re PR c++/79085 (ICE with placement new to unaligned location)
X-Git-Tag: releases/gcc-6.5.0~208
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a4b178f3d6569620cb1c0422d4a867de455e9474;p=thirdparty%2Fgcc.git

backport: re PR c++/79085 (ICE with placement new to unaligned location)

	Backported from mainline
	2018-03-15  Jakub Jelinek  <jakub@redhat.com>

	PR c++/79085
	* calls.c (expand_call): For TREE_ADDRESSABLE rettype ignore alignment
	check and use address of target always.

	* g++.dg/opt/pr79085.C: New test.

From-SVN: r262076
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6923e64fbde2..070fee57a60b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,12 @@
 2018-06-25  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	2018-03-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/79085
+	* calls.c (expand_call): For TREE_ADDRESSABLE rettype ignore alignment
+	check and use address of target always.
+
 	2018-03-09  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/84772
diff --git a/gcc/calls.c b/gcc/calls.c
index c78059fb5199..30c74ec961f8 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -2557,9 +2557,14 @@ expand_call (tree exp, rtx target, int ignore)
 	if (CALL_EXPR_RETURN_SLOT_OPT (exp)
 	    && target
 	    && MEM_P (target)
-	    && !(MEM_ALIGN (target) < TYPE_ALIGN (rettype)
-		 && SLOW_UNALIGNED_ACCESS (TYPE_MODE (rettype),
-					   MEM_ALIGN (target))))
+	    /* If rettype is addressable, we may not create a temporary.
+	       If target is properly aligned at runtime and the compiler
+	       just doesn't know about it, it will work fine, otherwise it
+	       will be UB.  */
+	    && (TREE_ADDRESSABLE (rettype)
+		|| !(MEM_ALIGN (target) < TYPE_ALIGN (rettype)
+		     && SLOW_UNALIGNED_ACCESS (TYPE_MODE (rettype),
+					       MEM_ALIGN (target)))))
 	  structure_value_addr = XEXP (target, 0);
 	else
 	  {
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8f9eb960f9d2..818d6b60c4c2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -3,6 +3,9 @@
 	Backported from mainline
 	2018-03-15  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/79085
+	* g++.dg/opt/pr79085.C: New test.
+
 	PR c++/84222
 	* g++.dg/warn/deprecated.C (T::member3): Change dg-warning to dg-bogus.
 	* g++.dg/warn/deprecated-6.C (T::member3): Likewise.
diff --git a/gcc/testsuite/g++.dg/opt/pr79085.C b/gcc/testsuite/g++.dg/opt/pr79085.C
new file mode 100644
index 000000000000..1d75d6a73009
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr79085.C
@@ -0,0 +1,24 @@
+// PR c++/79085
+// { dg-do compile }
+// { dg-options "-Os" }
+// { dg-additional-options "-mstrict-align" { target { aarch64*-*-* powerpc*-*-linux* powerpc*-*-elf* } } }
+
+void *operator new (__SIZE_TYPE__, void *p) { return p; }
+
+struct S
+{
+  S ();
+  S (const S &);
+  ~S (void);
+  int i;
+};
+
+S foo ();
+
+static char buf [sizeof (S) + 1];
+
+S *
+bar ()
+{
+  return new (buf + 1) S (foo ());
+}