mirror/binutils-gdb
2
0
Fork 0
mirror of https://sourceware.org/git/binutils-gdb.git synced 2025-02-17 13:10:12 +08:00
Code Issues Packages Projects Releases Wiki Activity

Handle optimizer code motions into the prologue.

Browse Source
This commit is contained in:
Kevin Buettner 2000-11-18 05:50:11 +00:00
parent ba5f58cb2e
commit 55d05f3b1d
2 changed files with 113 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
gdb/ChangeLog
View File

@ -1,3 +1,15 @@
2000-11-17 Kevin Buettner <kevinb@redhat.com>
* rs6000-tdep.c (refine_prologue_limit): New function.
(skip_prologue): When zero, attempt to obtain value for
lim_pc by calling refine_prologue_limit(). Also, fix
fencepost error regarding the limit in the loop.
From Peter Schauer:
* rs6000-tdep.c (skip_prologue): Handle optimizer code motions into
the prologue by continuing the prologue search, if we have no valid
frame yet or if the return address is not yet saved in the frame.
2000-11-17 Kevin Buettner <kevinb@redhat.com>
* wrapper.c (gdb_value_assign, wrap_value_assign): Protoize.

107
gdb/rs6000-tdep.c
View File

@ -380,11 +380,63 @@ rs6000_software_single_step (unsigned int signal, int insert_breakpoints_p)
#define GET_SRC_REG(x) (((x) >> 21) & 0x1f)
/* Limit the number of skipped non-prologue instructions, as the examining
of the prologue is expensive. */
static int max_skip_non_prologue_insns = 10;
/* Given PC representing the starting address of a function, and
LIM_PC which is the (sloppy) limit to which to scan when looking
for a prologue, attempt to further refine this limit by using
the line data in the symbol table. If successful, a better guess
on where the prologue ends is returned, otherwise the previous
value of lim_pc is returned. */
static CORE_ADDR
refine_prologue_limit (CORE_ADDR pc, CORE_ADDR lim_pc)
{
struct symtab_and_line prologue_sal;
prologue_sal = find_pc_line (pc, 0);
if (prologue_sal.line != 0)
{
int i;
CORE_ADDR addr = prologue_sal.end;
/* Handle the case in which compiler's optimizer/scheduler
has moved instructions into the prologue. We scan ahead
in the function looking for address ranges whose corresponding
line number is less than or equal to the first one that we
found for the function. (It can be less than when the
scheduler puts a body instruction before the first prologue
instruction.) */
for (i = 2 * max_skip_non_prologue_insns;
i > 0 && (lim_pc == 0 || addr < lim_pc);
i--)
{
struct symtab_and_line sal;
sal = find_pc_line (addr, 0);
if (sal.line == 0)
break;
if (sal.line <= prologue_sal.line
&& sal.symtab == prologue_sal.symtab)
{
prologue_sal = sal;
}
addr = sal.end;
}
if (lim_pc == 0 || prologue_sal.end < lim_pc)
lim_pc = prologue_sal.end;
}
return lim_pc;
}
static CORE_ADDR
skip_prologue (CORE_ADDR pc, CORE_ADDR lim_pc, struct rs6000_framedata *fdata)
{
CORE_ADDR orig_pc = pc;
CORE_ADDR last_prologue_pc;
CORE_ADDR last_prologue_pc = pc;
char buf[4];
unsigned long op;
long offset = 0;
@ -394,6 +446,22 @@ skip_prologue (CORE_ADDR pc, CORE_ADDR lim_pc, struct rs6000_framedata *fdata)
int framep = 0;
int minimal_toc_loaded = 0;
int prev_insn_was_prologue_insn = 1;
int num_skip_non_prologue_insns = 0;
/* Attempt to find the end of the prologue when no limit is specified.
Note that refine_prologue_limit() has been written so that it may
be used to "refine" the limits of non-zero PC values too, but this
is only safe if we 1) trust the line information provided by the
compiler and 2) iterate enough to actually find the end of the
prologue.
It may become a good idea at some point (for both performance and
accuracy) to unconditionally call refine_prologue_limit(). But,
until we can make a clear determination that this is beneficial,
we'll play it safe and only use it to obtain a limit when none
has been specified. */
if (lim_pc == 0)
lim_pc = refine_prologue_limit (pc, lim_pc);
memset (fdata, 0, sizeof (struct rs6000_framedata));
fdata->saved_gpr = -1;
@ -402,19 +470,22 @@ skip_prologue (CORE_ADDR pc, CORE_ADDR lim_pc, struct rs6000_framedata *fdata)
fdata->frameless = 1;
fdata->nosavedpc = 1;
pc -= 4;
while (lim_pc == 0 || pc < lim_pc - 4)
for (;; pc += 4)
{
pc += 4;
/* Sometimes it isn't clear if an instruction is a prologue
instruction or not. When we encounter one of these ambiguous
cases, we'll set prev_insn_was_prologue_insn to 0 (false).
Otherwise, we'll assume that it really is a prologue instruction. */
if (prev_insn_was_prologue_insn)
last_prologue_pc = pc;
/* Stop scanning if we've hit the limit. */
if (lim_pc != 0 && pc >= lim_pc)
break;
prev_insn_was_prologue_insn = 1;
/* Fetch the instruction and convert it to an integer. */
if (target_read_memory (pc, buf, 4))
break;
op = extract_signed_integer (buf, 4);
@ -628,7 +699,31 @@ skip_prologue (CORE_ADDR pc, CORE_ADDR lim_pc, struct rs6000_framedata *fdata)
}
else
{
break;
/* Not a recognized prologue instruction.
Handle optimizer code motions into the prologue by continuing
the search if we have no valid frame yet or if the return
address is not yet saved in the frame. */
if (fdata->frameless == 0
&& (lr_reg == -1 || fdata->nosavedpc == 0))
break;
if (op == 0x4e800020 /* blr */
|| op == 0x4e800420) /* bctr */
/* Do not scan past epilogue in frameless functions or
trampolines. */
break;
if ((op & 0xf4000000) == 0x40000000) /* bxx */
/* Never skip branches. */
break;
if (num_skip_non_prologue_insns++ > max_skip_non_prologue_insns)
/* Do not scan too many insns, scanning insns is expensive with
remote targets. */
break;
/* Continue scanning. */
prev_insn_was_prologue_insn = 0;
continue;
}
}