There is no CFA information generated for instructions which manipulate the
stack during function epilogues. This means a debugger cannot determine the
position of variables on the stack whilst the epilogue is in progress.
This can cause the debugger to give erroneous information when printing a
backtrace whilst stepping through the epilogue, or cause software watchpoints
set on stack variables to become invalidated after a function epilogue
is executed.
The patch fixes this by marking stack manipulation insns as
frame_related, and adding reg_note RTXs to stack pop instructions in the
epilogue.
Successfully regtested on trunk for msp430-elf in the default, -mlarge,
-mcpu=msp430 and -mlarge/-mcode-region=either/-mdata-region=either
configurations.
This fixes some tests from watchpoint.exp in the GDB testsuite.
Ok for trunk?
Thanks,
Jozef
>From 272b38a374eddf7327a61ff9b1730f0a2dd40233 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <joze...@mittosystems.com>
Date: Mon, 7 Sep 2020 20:34:40 +0100
Subject: [PATCH] MSP430: Fix CFA generation during function epilogues
There is no CFA information generated for instructions which manipulate the
stack during function epilogues. This means a debugger cannot determine the
position of variables on the stack whilst the epilogue is in progress.
This can cause the debugger to give erroneous information when printing a
backtrace whilst stepping through the epilogue, or cause software watchpoints
set on stack variables to become invalidated after a function epilogue
is executed.
The patch fixes this by marking stack manipulation insns as
frame_related, and adding reg_note RTXs to stack pop instructions in the
epilogue.
gcc/ChangeLog:
* config/msp430/msp430.c (increment_stack): Mark insns which increment
the stack as frame_related.
(msp430_expand_prologue): Add comments.
(msp430_expand_epilogue): Mark insns which decrement
the stack as frame_related.
Add reg_note to stack pop insns describing position of register
variables on the stack.
---
gcc/config/msp430/msp430.c | 72 +++++++++++++++++++++++++++++++-------
1 file changed, 59 insertions(+), 13 deletions(-)
diff --git a/gcc/config/msp430/msp430.c b/gcc/config/msp430/msp430.c
index 129b916715e..1cb1b8f8626 100644
--- a/gcc/config/msp430/msp430.c
+++ b/gcc/config/msp430/msp430.c
@@ -1700,9 +1700,9 @@ increment_stack (HOST_WIDE_INT amount)
{
inc = GEN_INT (amount);
if (TARGET_LARGE)
- emit_insn (gen_addpsi3 (sp, sp, inc));
+ F (emit_insn (gen_addpsi3 (sp, sp, inc)));
else
- emit_insn (gen_addhi3 (sp, sp, inc));
+ F (emit_insn (gen_addhi3 (sp, sp, inc)));
}
}
@@ -2413,6 +2413,8 @@ msp430_expand_prologue (void)
for (i = 15; i >= 4; i--)
if (cfun->machine->need_to_save[i])
{
+ /* We need to save COUNT sequential registers starting from regnum
+ I. */
int seq, count;
rtx note;
@@ -2427,6 +2429,7 @@ msp430_expand_prologue (void)
p = F (emit_insn (gen_pushm (gen_rtx_REG (Pmode, i),
GEN_INT (count))));
+ /* Document the stack decrement as a result of PUSHM. */
note = gen_rtx_SEQUENCE (VOIDmode, rtvec_alloc (count + 1));
XVECEXP (note, 0, 0)
@@ -2475,8 +2478,10 @@ msp430_expand_prologue (void)
void
msp430_expand_epilogue (int is_eh)
{
- int i;
+ int i, j;
int fs;
+ rtx sp = stack_pointer_rtx;
+ rtx p;
int helper_n = 0;
if (is_naked_func ())
@@ -2545,19 +2550,27 @@ msp430_expand_epilogue (int is_eh)
for (i = 4; i <= 15; i++)
if (cfun->machine->need_to_save[i])
{
- int seq, count;
+ /* We need to restore COUNT sequential registers starting from regnum
+ I. */
+ int seq;
+ int count = 1;
+ int helper_used = 0;
+ rtx note, addr;
- for (seq = i + 1; seq <= 15 && cfun->machine->need_to_save[seq]; seq ++)
- ;
- count = seq - i;
+ if (msp430x)
+ {
+ for (seq = i + 1; seq <= 15 && cfun->machine->need_to_save[seq];
+ seq++)
+ ;
+ count = seq - i;
+ }
if (msp430x)
{
/* Note: With TARGET_LARGE we still use
POPM as POPX.A is two bytes bigger. */
- emit_insn (gen_popm (stack_pointer_rtx, GEN_INT (seq - 1),
- GEN_INT (count)));
- i += count - 1;
+ p = F (emit_insn (gen_popm (stack_pointer_rtx, GEN_INT (seq - 1),
+ GEN_INT (count))));
}
else if (i == 11 - helper_n
&& ! msp430_is_interrupt_func ()
@@ -2569,11 +2582,44 @@ msp430_expand_epilogue (int is_eh)
&& helper_n > 1
&& !is_eh)
{
- emit_jump_insn (gen_epilogue_helper (GEN_INT (helper_n)));
- return;
+ p = F (emit_jump_insn (gen_epilogue_helper (GEN_INT (helper_n))));
+ count = helper_n;
+ helper_used = 1;
}
else
- emit_insn (gen_pop (gen_rtx_REG (Pmode, i)));
+ p = F (emit_insn (gen_pop (gen_rtx_REG (Pmode, i))));
+
+ /* Document the stack increment as a result of POPM. */
+ note = gen_rtx_SEQUENCE (VOIDmode, rtvec_alloc (count + 1));
+
+ addr = gen_rtx_PLUS (Pmode, stack_pointer_rtx,
+ GEN_INT (count * (TARGET_LARGE ? 4 : 2)));
+
+ XVECEXP (note, 0, 0) = F (gen_rtx_SET (stack_pointer_rtx, addr));
+
+
+ /* *sp++ = R[i+j] */
+ /* sp R4
+ ...
+ sp+N R10. */
+ for (j = 0; j < count; j++)
+ {
+ int ofs = j * (TARGET_LARGE ? 4 : 2);
+
+ if (ofs)
+ addr = gen_rtx_PLUS (Pmode, sp, GEN_INT (ofs));
+ else
+ addr = stack_pointer_rtx;
+
+ XVECEXP (note, 0, j + 1)
+ = F (gen_rtx_SET (gen_rtx_MEM (Pmode, addr),
+ gen_rtx_REG (Pmode, i + j)));
+ }
+ add_reg_note (p, REG_FRAME_RELATED_EXPR, note);
+ i += count - 1;
+
+ if (helper_used)
+ return;
}
if (is_eh)
--
2.28.0
