diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 27a236b9243..59636dbc6c4 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,8 @@
+2007-02-08  Roger Sayle  <roger@eyesopen.com>
+
+	* trans-stmt.c (gfc_trans_forall_1): Optimize the cases where the
+	mask expression is a compile-time constant (".true." or ".false.").
+
 2007-02-04  Francois-Xavier Coudert  <coudert@clipper.ens.fr>
 
 	PR fortran/30611
diff --git a/gcc/fortran/trans-stmt.c b/gcc/fortran/trans-stmt.c
index daf68db4246..db92c02d3d4 100644
--- a/gcc/fortran/trans-stmt.c
+++ b/gcc/fortran/trans-stmt.c
@@ -2458,6 +2458,13 @@ gfc_trans_forall_1 (gfc_code * code, forall_info * nested_forall_info)
   gfc_saved_var *saved_vars;
   iter_info *this_forall;
   forall_info *info;
+  bool need_mask;
+
+  /* Do nothing if the mask is false.  */
+  if (code->expr
+      && code->expr->expr_type == EXPR_CONSTANT
+      && !code->expr->value.logical)
+    return build_empty_stmt ();
 
   n = 0;
   /* Count the FORALL index number.  */
@@ -2557,8 +2564,20 @@ gfc_trans_forall_1 (gfc_code * code, forall_info * nested_forall_info)
   info->nvar = nvar;
   info->size = size;
 
-  /* First we need to allocate the mask.  */
   if (code->expr)
+    {
+      /* If the mask is .true., consider the FORALL unconditional.  */
+      if (code->expr->expr_type == EXPR_CONSTANT
+	  && code->expr->value.logical)
+	need_mask = false;
+      else
+	need_mask = true;
+    }
+  else
+    need_mask = false;
+
+  /* First we need to allocate the mask.  */
+  if (need_mask)
     {
       /* As the mask array can be very big, prefer compact boolean types.  */
       tree mask_type = gfc_get_logical_type (gfc_logical_kinds[0].kind);
@@ -2583,7 +2602,7 @@ gfc_trans_forall_1 (gfc_code * code, forall_info * nested_forall_info)
 
   /* Copy the mask into a temporary variable if required.
      For now we assume a mask temporary is needed.  */
-  if (code->expr)
+  if (need_mask)
     {
       /* As the mask array can be very big, prefer compact boolean types.  */
       tree mask_type = gfc_get_logical_type (gfc_logical_kinds[0].kind);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ce9a32015a1..8454452f303 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2007-02-08  Roger Sayle  <roger@eyesopen.com>
+
+	* gfortran.dg/forall_8.f90: New test case.
+	* gfortran.dg/forall_9.f90: Likewise.
+
 2007-02-07  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* gcc.dg/builtins-20.c: Add some -~ complex cases.
diff --git a/gcc/testsuite/gfortran.dg/forall_8.f90 b/gcc/testsuite/gfortran.dg/forall_8.f90
new file mode 100644
index 00000000000..b06f3028a0f
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/forall_8.f90
@@ -0,0 +1,9 @@
+! { dg-do compile }
+! { dg-options "-O2 -fdump-tree-original" }
+  integer a(100)
+  forall (i=1:100,.true.)
+      a(i) = 0
+  end forall
+  end
+! { dg-final { scan-tree-dump-times "temp" 0 "original" } }
+! { dg-final { cleanup-tree-dump "original" } }
diff --git a/gcc/testsuite/gfortran.dg/forall_9.f90 b/gcc/testsuite/gfortran.dg/forall_9.f90
new file mode 100644
index 00000000000..12084b16744
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/forall_9.f90
@@ -0,0 +1,9 @@
+! { dg-do compile }
+! { dg-options "-O2 -fdump-tree-original" }
+  integer a(100)
+  forall (i=1:100,.false.)
+      a(i) = 0
+  end forall
+  end
+! { dg-final { scan-tree-dump-times "temp" 0 "original" } }
+! { dg-final { cleanup-tree-dump "original" } }