From: Thomas Koenig <tkoenig@gcc.gnu.org>
Date: Thu, 7 Jun 2012 14:33:51 +0000 (+0000)
Subject: re PR fortran/52861 ((missed optimisation) missed transformation to memset with -O3)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=1acbf7a1bfb1bddb24ea3fc3710f0ddbb097aa72;p=gcc.git

re PR fortran/52861 ((missed optimisation) missed transformation to memset with -O3)

2012-06-07  Thomas König  <tkoenig@gcc.gnu.org>

	PR fortran/52861
	* frontend-passes.c (optimize_assignment):  Don't set the
	length of an empty string for deferred-length character
	variables.

2012-06-07  Thomas König  <tkoenig@gcc.gnu.org>

	PR fortran/52861
	* gfortran.dg/string_assign_2.f90:  New test case.

From-SVN: r188305
---

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index c882a416a9f..e51d5071d83 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,7 +1,14 @@
 2012-06-07  Thomas König  <tkoenig@gcc.gnu.org>
 
 	PR fortran/52861
-	* frontend-passes (empty_string):  Add prototype.
+	* frontend-passes.c (optimize_assignment):  Don't set the
+	length of an empty string for deferred-length character
+	variables.
+
+2012-06-07  Thomas König  <tkoenig@gcc.gnu.org>
+
+	PR fortran/52861
+	* frontend-passes.c (empty_string):  Add prototype.
 	(optimize_assignment):  Set the length of an empty string
 	constant to zero.
 
diff --git a/gcc/fortran/frontend-passes.c b/gcc/fortran/frontend-passes.c
index 4fd24c2947e..bcc1bdc323b 100644
--- a/gcc/fortran/frontend-passes.c
+++ b/gcc/fortran/frontend-passes.c
@@ -740,8 +740,10 @@ optimize_assignment (gfc_code * c)
       /* Optimize away a = trim(b), where a is a character variable.  */
       remove_trim (rhs);
 
-      /* Replace a = '   ' by a = '' to optimize away a memcpy.  */
-      if (empty_string(rhs))
+      /* Replace a = '   ' by a = '' to optimize away a memcpy, but only
+	 for strings with non-deferred length (otherwise we would
+	 reallocate the length.  */
+      if (empty_string(rhs) && ! lhs->ts.deferred)
 	rhs->value.character.length = 0;
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5819c0067c4..776012c569b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2012-06-07  Thomas König  <tkoenig@gcc.gnu.org>
+
+	PR fortran/52861
+	* gfortran.dg/string_assign_2.f90:  New test case.
+
 2012-06-07  Thomas König  <tkoenig@gcc.gnu.org>
 
 	PR fortran/52861
diff --git a/gcc/testsuite/gfortran.dg/string_assign_2.f90 b/gcc/testsuite/gfortran.dg/string_assign_2.f90
new file mode 100644
index 00000000000..f3cfa45e0de
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/string_assign_2.f90
@@ -0,0 +1,9 @@
+! { dg-do run }
+! { dg-options "-ffrontend-optimize" }
+program main
+  character (len=:), allocatable :: a
+  a = 'a'
+  if (len(a) /= 1) call abort
+  a = '  '
+  if (len(a) /= 2) call abort
+end program main