xtensa: libgcc: fix PR target/95571

Rewrite uw_install_context without function calls to avoid register
spilling in _Unwind_RaiseException during return context installation.

2020-06-08  Max Filippov  <jcmvbkbc@gmail.com>
gcc/testsuite/
	* g++.target/xtensa/pr95571.C: New test.
	* g++.target/xtensa/xtensa.exp: New testsuite.

libgcc/
	* config/xtensa/unwind-dw2-xtensa.c (uw_install_context): Merge
	with uw_install_context_1.

diff --git a/gcc/testsuite/g++.target/xtensa/pr95571.C b/gcc/testsuite/g++.target/xtensa/pr95571.C
new file mode 100644 (file)
index 0000000..59fe285
--- /dev/null
+++ b/gcc/testsuite/g++.target/xtensa/pr95571.C
@@ -0,0 +1,43 @@
+/* { dg-do run } */
+
+extern "C" void abort(void);
+extern "C" void __xtensa_libgcc_window_spill(void);
+
+static int call;
+static int cnt;
+
+extern "C" void *memcpy(void *dst, const void *src, unsigned int sz)
+{
+  char *a = (char *)dst;
+  const char *b = (const char *)src;
+
+  if (call++ == cnt)
+    __xtensa_libgcc_window_spill();
+
+  while (sz--)
+    *a++ = *b++;
+
+  return dst;
+}
+
+int main()
+{
+  int i;
+
+  for (i = 0; i < 100; ++i)
+    {
+      call = 0;
+      cnt = i;
+
+      try
+       {
+         throw 1;
+       }
+      catch (int v)
+       {
+         if (v != 1)
+           abort ();
+       }
+    }
+  return 0;
+}

diff --git a/gcc/testsuite/g++.target/xtensa/xtensa.exp b/gcc/testsuite/g++.target/xtensa/xtensa.exp
new file mode 100644 (file)
index 0000000..f419120
--- /dev/null
+++ b/gcc/testsuite/g++.target/xtensa/xtensa.exp
@@ -0,0 +1,43 @@
+#  Specific regression driver for Xtensa.
+#  Copyright (C) 2020 Free Software Foundation, Inc.
+#
+#  This file is part of GCC.
+#
+#  GCC is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 3, or (at your option)
+#  any later version.
+#
+#  GCC is distributed in the hope that it will be useful, but
+#  WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+#  General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with GCC; see the file COPYING3.  If not see
+#  <http://www.gnu.org/licenses/>.  */
+
+# GCC testsuite that uses the `dg.exp' driver.
+
+# Exit immediately if this isn't an Xtensa target.
+if {![istarget xtensa*-*-*] } then {
+  return
+}
+
+# Load support procs.
+load_lib g++-dg.exp
+
+global DEFAULT_CXXFLAGS
+if ![info exists DEFAULT_CXXFLAGS] then {
+    set DEFAULT_CXXFLAGS " -pedantic-errors"
+}
+
+# Initialize `dg'.
+dg-init
+
+# Main loop.
+dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.C]] \
+        "" $DEFAULT_CXXFLAGS
+
+# All done.
+dg-finish

diff --git a/libgcc/config/xtensa/unwind-dw2-xtensa.c b/libgcc/config/xtensa/unwind-dw2-xtensa.c
index 056182a794aab63336653dce6f0d6fa3726f391e..8a6a44a8b685ae182227aa989bc9a4a6c0b7e9d5 100644 (file)
--- a/libgcc/config/xtensa/unwind-dw2-xtensa.c
+++ b/libgcc/config/xtensa/unwind-dw2-xtensa.c
@@ -481,37 +481,35 @@ uw_init_context_1 (struct _Unwind_Context *context, void *outer_cfa,
 
 /* Install TARGET into CURRENT so that we can return to it.  This is a
    macro because __builtin_eh_return must be invoked in the context of
-   our caller.  */
+   our caller, and also because spilling registers of the caller before
+   the context installation may result in reload of wrong register values
+   after the context installation due to the change of the stack pointer
+   in the base save area.  This spilling may be caused by an interrupt
+   handler on baremetal host.  */
 
-#define uw_install_context(CURRENT, TARGET, FRAMES)                             \
+#define uw_install_context(CURRENT, TARGET, FRAMES)                     \
   do                                                                    \
     {                                                                   \
-      long offset = uw_install_context_1 ((CURRENT), (TARGET));                 \
       void *handler = __builtin_frob_return_addr ((TARGET)->ra);        \
-      __builtin_eh_return (offset, handler);                            \
+      long i;                                                           \
+                                                                        \
+      /* The eh_return insn assumes a window size of 8, so don't bother         \
+        copying the save areas for registers a8-a15 since they won't be \
+        reloaded.  */                                                   \
+      for (i = 0; i < 2; ++i)                                           \
+       {                                                                \
+         _Unwind_Word *c = (CURRENT)->reg[i];                           \
+         _Unwind_Word *t = (TARGET)->reg[i];                            \
+         int j;                                                         \
+                                                                        \
+         if (t && c && t != c)                                          \
+           for (j = 0; j < 4; ++j)                                      \
+             *c++ = *t++;                                               \
+       }                                                                \
+      __builtin_eh_return (0, handler);                                         \
     }                                                                   \
   while (0)
 
-static long
-uw_install_context_1 (struct _Unwind_Context *current,
-                     struct _Unwind_Context *target)
-{
-  long i;
-
-  /* The eh_return insn assumes a window size of 8, so don't bother copying
-     the save areas for registers a8-a15 since they won't be reloaded.  */
-  for (i = 0; i < 2; ++i)
-    {
-      void *c = current->reg[i];
-      void *t = target->reg[i];
-
-      if (t && c && t != c)
-       memcpy (c, t, 4 * sizeof (_Unwind_Word));
-    }
-
-  return 0;
-}
-
 static inline _Unwind_Ptr
 uw_identify_context (struct _Unwind_Context *context)
 {