On Sat, Sep 01, 2018 at 06:38:35AM -0500, Segher Boessenkool wrote:
> >
> > With -fno-omit-frame-pointer, arg pointer is eliminated with hard frame
> > pointer. But
> >
> > 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.
> >
> > changed it in the last minute. It is too late to go back. When it is done,
> > hard frame pointer must be replaced by stack pointer - UNITS_PER_WORD
> > if it is ever used.
>
> So after that patch something uses the hard frame pointer, while it also
> claims nothing uses the hard frame pointer? Sounds to me you should fix
> the uses, and all will be fine.
>
>
Here is the patch to replace hard frame pointer with stack pointer
- UNITS_PER_WORD in x86 backend.
OK for trunk?
H.J.
---
With
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 in debug info may be eliminated
by hard frame pointer. In this case, hard frame pointer should be
replaced by stack pointer - UNITS_PER_WORD.
This patch adds replace_fp_with_sp_in_debug_info to x86 machine_function,
replaces arg pointer in debug info with stack pointer - UNITS_PER_WORD
if it is eliminated by hard frame pointer and disallows hard frame pointer
in debug info when frame pointer isn't available.
gcc/
PR debug/86593
* dwarf2out.c (based_loc_descr): Disallow hard frame pointer when
frame pointer isn't available.
(compute_frame_pointer_to_fb_displacement): Likewise.
* config/i386/i386.c (ix86_finalize_stack_frame_flags): Set
replace_fp_with_sp_in_debug_info to true if frame pointer isn't
used.
(ix86_replace_fp_with_sp_1): New function.
(ix86_replace_fp_with_sp): Likewise.
(ix86_reorg): Call ix86_replace_fp_with_sp if needed.
* config/i386/i386.h (machine_function): Add
replace_fp_with_sp_in_debug_info.
gcc/testsuite/
PR debug/86593
* g++.dg/pr86593-1.C: New test.
* g++.dg/pr86593-2.C: Likewise.
---
gcc/config/i386/i386.c | 103 +++++++++++++++++++++++++++++++
gcc/config/i386/i386.h | 4 ++
gcc/dwarf2out.c | 6 +-
gcc/testsuite/g++.dg/pr86593-1.C | 11 ++++
gcc/testsuite/g++.dg/pr86593-2.C | 11 ++++
5 files changed, 131 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/pr86593-1.C
create mode 100644 gcc/testsuite/g++.dg/pr86593-2.C
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 8672a666024..8166ea06d42 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -13161,6 +13161,11 @@ ix86_finalize_stack_frame_flags (void)
df_compute_regs_ever_live (true);
df_analyze ();
+ /* Replace hard frame pointer with stack pointer in debug
+ info. */
+ cfun->machine->replace_fp_with_sp_in_debug_info
+ = debug_info_level > DINFO_LEVEL_NONE;
+
if (flag_var_tracking)
{
/* Since frame pointer is no longer available, replace it with
@@ -41944,6 +41949,99 @@ ix86_seh_fixup_eh_fallthru (void)
}
}
+/* Help function for ix86_replace_fp_with_sp. */
+
+static rtx
+ix86_replace_fp_with_sp_1 (rtx x)
+{
+ if (!x)
+ return x;
+
+ if (x == hard_frame_pointer_rtx)
+ return plus_constant (Pmode, stack_pointer_rtx, -UNITS_PER_WORD);
+
+ const char *fmt = GET_RTX_FORMAT (GET_CODE (x));
+ int i, j;
+ for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
+ {
+ if (fmt[i] == 'e')
+ XEXP (x, i) = ix86_replace_fp_with_sp_1 (XEXP (x, i));
+ else if (fmt[i] == 'E')
+ for (j = XVECLEN (x, i) - 1; j >= 0; j--)
+ XVECEXP (x, i, j) = ix86_replace_fp_with_sp_1 (XVECEXP (x, i, j));
+ }
+
+ return x;
+}
+
+/* Replace hard frame pointer in debug info with stack pointer
+ - UNITS_PER_WORD. */
+
+static void
+ix86_replace_fp_with_sp (void)
+{
+ if (flag_var_tracking)
+ {
+ rtx_insn *insn, *next;
+ rtx replace, note;
+ for (insn = get_insns (); insn; insn = next)
+ {
+ next = NEXT_INSN (insn);
+ if (NOTE_P (insn))
+ {
+ if (NOTE_KIND (insn) == NOTE_INSN_VAR_LOCATION)
+ {
+ replace = PATTERN (insn);
+ if (reg_mentioned_p (arg_pointer_rtx, replace))
+ {
+ replace = eliminate_regs (replace, VOIDmode,
+ NULL_RTX);
+ if (reg_mentioned_p (hard_frame_pointer_rtx,
+ replace))
+ {
+ ix86_replace_fp_with_sp_1 (replace);
+ PATTERN (insn) = replace;
+ }
+ }
+ }
+ }
+ else if (CALL_P (insn))
+ {
+ note = find_reg_note (insn, REG_CALL_ARG_LOCATION,
+ NULL_RTX);
+ if (note && reg_mentioned_p (arg_pointer_rtx, note))
+ {
+ replace = eliminate_regs (XEXP (note, 0), VOIDmode,
+ NULL_RTX);
+ if (reg_mentioned_p (hard_frame_pointer_rtx, replace))
+ {
+ ix86_replace_fp_with_sp_1 (replace);
+ remove_note (insn, note);
+ add_reg_note (insn, REG_CALL_ARG_LOCATION,
+ replace);
+ }
+ }
+ }
+ }
+ }
+
+ for (tree arg = DECL_ARGUMENTS (current_function_decl);
+ arg;
+ arg = TREE_CHAIN (arg))
+ {
+ rtx incoming = DECL_INCOMING_RTL (arg);
+ if (reg_mentioned_p (arg_pointer_rtx, incoming))
+ {
+ incoming = eliminate_regs (incoming, VOIDmode, NULL_RTX);
+ if (reg_mentioned_p (hard_frame_pointer_rtx, incoming))
+ {
+ ix86_replace_fp_with_sp_1 (incoming);
+ DECL_INCOMING_RTL (arg) = incoming;
+ }
+ }
+ }
+}
+
/* Implement machine specific optimizations. We implement padding of returns
for K8 CPUs and pass to avoid 4 jumps in the single 16 byte window. */
static void
@@ -41956,6 +42054,11 @@ ix86_reorg (void)
if (TARGET_SEH && current_function_has_exception_handlers ())
ix86_seh_fixup_eh_fallthru ();
+ /* Replace hard frame pointer in debug info with stack pointer
+ - UNITS_PER_WORD after the variable tracking pass. */
+ if (cfun->machine->replace_fp_with_sp_in_debug_info)
+ ix86_replace_fp_with_sp ();
+
if (optimize && optimize_function_for_speed_p (cfun))
{
if (TARGET_PAD_SHORT_FUNCTION)
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 2a46fccdec1..23cef7a9c61 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -2610,6 +2610,10 @@ struct GTY(()) machine_function {
/* Nonzero if the function places outgoing arguments on stack. */
BOOL_BITFIELD outgoing_args_on_stack : 1;
+ /* If true, replace hard frame pointer with stack pointer in debug
+ info. */
+ BOOL_BITFIELD replace_fp_with_sp_in_debug_info : 1;
+
/* The largest alignment, in bytes, of stack slot actually used. */
unsigned int max_used_stack_alignment;
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 77317ed2575..a879ac1f18c 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -14327,8 +14327,7 @@ based_loc_descr (rtx reg, poly_int64 offset,
{
elim = strip_offset_and_add (elim, &offset);
gcc_assert ((SUPPORTS_STACK_ALIGNMENT
- && (elim == hard_frame_pointer_rtx
- || elim == stack_pointer_rtx))
+ && elim == stack_pointer_rtx)
|| elim == (frame_pointer_needed
? hard_frame_pointer_rtx
: stack_pointer_rtx));
@@ -20515,8 +20514,7 @@ compute_frame_pointer_to_fb_displacement (poly_int64
offset)
frame_pointer_fb_offset, we won't need one either. */
frame_pointer_fb_offset_valid
= ((SUPPORTS_STACK_ALIGNMENT
- && (elim == hard_frame_pointer_rtx
- || elim == stack_pointer_rtx))
+ && elim == stack_pointer_rtx)
|| elim == (frame_pointer_needed
? hard_frame_pointer_rtx
: stack_pointer_rtx));
diff --git a/gcc/testsuite/g++.dg/pr86593-1.C b/gcc/testsuite/g++.dg/pr86593-1.C
new file mode 100644
index 00000000000..31dc4153cb9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr86593-1.C
@@ -0,0 +1,11 @@
+// { dg-options "-O -g -fno-omit-frame-pointer -fvar-tracking" }
+
+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;
+}
diff --git a/gcc/testsuite/g++.dg/pr86593-2.C b/gcc/testsuite/g++.dg/pr86593-2.C
new file mode 100644
index 00000000000..65aeac98099
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr86593-2.C
@@ -0,0 +1,11 @@
+// { dg-options "-O -g -fno-omit-frame-pointer -fno-var-tracking" }
+
+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;
+}
--
2.17.1
