DWARF: Allow hard frame pointer even if frame pointer isn't used

r251028

commit cd557ff63f388ad27c376d0a225e74d3594a6f9d
Author: hjl <hjl@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Thu Aug 10 15:29:05 2017 +0000

    i386: Don't use frame pointer without stack access

    When there is no stack access, there is no need to use frame pointer
    even if -fno-omit-frame-pointer is used and caller's frame pointer is
    unchanged.

frame pointer may not be available even if -fno-omit-frame-pointer is
used.  When this happened, arg pointer may be eliminated by hard frame
pointer.  Since hard frame pointer is encoded with DW_OP_fbreg which
uses the DW_AT_frame_base attribute, not hard frame pointer directly,
we should allow hard frame pointer when generating DWARF info even if
frame pointer isn't used.

gcc/

	PR debug/86593
	* dwarf2out.c (based_loc_descr): Allow hard frame pointer even
	if frame pointer isn't used.
	(compute_frame_pointer_to_fb_displacement): Likewise.

gcc/testsuite/

	PR debug/86593
	* g++.dg/pr86593.C: New test.

From-SVN: r264096

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b00a869..4b19487 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-04  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR debug/86593
+       * dwarf2out.c (based_loc_descr): Allow hard frame pointer even
+       if frame pointer isn't used.
+       (compute_frame_pointer_to_fb_displacement): Likewise.
+
 2018-09-04  Jakub Jelinek  <jakub@redhat.com>
 
        PR target/87198

diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 77317ed..40cfdf5 100644 (file)
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -14325,13 +14325,13 @@ based_loc_descr (rtx reg, poly_int64 offset,
 
       if (elim != reg)
        {
+         /* Allow hard frame pointer here even if frame pointer
+           isn't used since hard frame pointer is encoded with
+           DW_OP_fbreg which uses the DW_AT_frame_base attribute,
+           not hard frame pointer directly.  */
          elim = strip_offset_and_add (elim, &offset);
-         gcc_assert ((SUPPORTS_STACK_ALIGNMENT
-                      && (elim == hard_frame_pointer_rtx
-                          || elim == stack_pointer_rtx))
-                     || elim == (frame_pointer_needed
-                                 ? hard_frame_pointer_rtx
-                                 : stack_pointer_rtx));
+         gcc_assert (elim == hard_frame_pointer_rtx
+                     || elim == stack_pointer_rtx);
 
          /* If drap register is used to align stack, use frame
             pointer + offset to access stack variables.  If stack
@@ -20512,14 +20512,13 @@ compute_frame_pointer_to_fb_displacement (poly_int64 offset)
      in which to eliminate.  This is because it's stack pointer isn't 
      directly accessible as a register within the ISA.  To work around
      this, assume that while we cannot provide a proper value for
-     frame_pointer_fb_offset, we won't need one either.  */
+     frame_pointer_fb_offset, we won't need one either.  We can use
+     hard frame pointer in debug info even if frame pointer isn't used
+     since hard frame pointer in debug info is encoded with DW_OP_fbreg
+     which uses the DW_AT_frame_base attribute, not hard frame pointer
+     directly.  */
   frame_pointer_fb_offset_valid
-    = ((SUPPORTS_STACK_ALIGNMENT
-       && (elim == hard_frame_pointer_rtx
-           || elim == stack_pointer_rtx))
-       || elim == (frame_pointer_needed
-                  ? hard_frame_pointer_rtx
-                  : stack_pointer_rtx));
+    = (elim == hard_frame_pointer_rtx || elim == stack_pointer_rtx);
 }
 
 /* Generate a DW_AT_name attribute given some string value to be included as

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 919c0e0..8b3578f 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-04  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR debug/86593
+       * g++.dg/pr86593.C: New test.
+
 2018-09-04  Jakub Jelinek  <jakub@redhat.com>
 
        PR target/87198

diff --git a/gcc/testsuite/g++.dg/pr86593.C b/gcc/testsuite/g++.dg/pr86593.C
new file mode 100644 (file)
index 0000000..feed8c3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr86593.C
@@ -0,0 +1,11 @@
+// { dg-options "-O -g -fno-omit-frame-pointer" }
+
+struct Foo
+{
+  int bar(int a, int b, int c, int i1, int i2, int i3, int d);
+};
+
+int Foo::bar(int a, int b, int c, int i1, int i2, int i3, int d)
+{
+  return 0;
+}