[PATCH 9/9] Force the use of stack_pointer_offset in computing the frame size.
Richard Henderson
rth@twiddle.net
Tue Aug 3 23:53:00 GMT 2010
By exporting padding[012] and to_allocate from ix86_compute_frame_layout,
we encouraged re-computation of the size of the local frame. All of the
truly relevant offsets are now exported directly, and should be compared
against directly.
---
gcc/config/i386/i386.c | 61 ++++++++++++++++-------------------------------
1 files changed, 21 insertions(+), 40 deletions(-)
* config/i386/i386.c (struct ix86_frame): Remove padding and
to_allocate members.
(ix86_compute_frame_layout): Don't store them.
(ix86_can_use_return_insn_p): Use a more direct and more obviously
correct condition for the position of the stack pointer.
(ix86_expand_prologue): Compute remaining stack allocation based
on the ultimate stack pointer offset.
(ix86_expand_epilogue): Use more obvious expressions testing for
the stack pointer already pointing to the saved registers.
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 47ab5e0..c6aef9b 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -1846,17 +1846,13 @@ struct GTY(()) stack_local_entry {
*/
struct ix86_frame
{
- int padding0;
int nsseregs;
int nregs;
- int padding1;
int va_arg_size;
int red_zone_size;
- HOST_WIDE_INT frame;
- int padding2;
int outgoing_arguments_size;
+ HOST_WIDE_INT frame;
- HOST_WIDE_INT to_allocate;
/* The offsets relative to ARG_POINTER. */
HOST_WIDE_INT frame_pointer_offset;
HOST_WIDE_INT hard_frame_pointer_offset;
@@ -7873,15 +7869,14 @@ ix86_can_use_return_insn_p (void)
if (! reload_completed || frame_pointer_needed)
return 0;
- /* Don't allow more than 32 pop, since that's all we can do
+ /* Don't allow more than 32k pop, since that's all we can do
with one instruction. */
- if (crtl->args.pops_args
- && crtl->args.size >= 32768)
+ if (crtl->args.pops_args && crtl->args.size >= 32768)
return 0;
ix86_compute_frame_layout (&frame);
- return frame.to_allocate == 0 && frame.padding0 == 0
- && (frame.nregs + frame.nsseregs) == 0;
+ return (frame.stack_pointer_offset == UNITS_PER_WORD
+ && (frame.nregs + frame.nsseregs) == 0);
}
/* Value should be nonzero if functions must have frame pointers.
@@ -8330,6 +8325,7 @@ ix86_compute_frame_layout (struct ix86_frame *frame)
HOST_WIDE_INT offset;
unsigned int preferred_alignment;
HOST_WIDE_INT size = get_frame_size ();
+ HOST_WIDE_INT to_allocate;
frame->nregs = ix86_nsaved_regs ();
frame->nsseregs = ix86_nsaved_sseregs ();
@@ -8416,14 +8412,12 @@ ix86_compute_frame_layout (struct ix86_frame *frame)
offset += frame->nregs * UNITS_PER_WORD;
frame->reg_save_offset = offset;
- /* Align SSE reg save area. */
+ /* Align and set SSE register save area. */
if (frame->nsseregs)
- frame->padding0 = ((offset + 16 - 1) & -16) - offset;
- else
- frame->padding0 = 0;
-
- /* SSE register save area. */
- offset += frame->padding0 + frame->nsseregs * 16;
+ {
+ offset = (offset + 16 - 1) & -16;
+ offset += frame->nsseregs * 16;
+ }
frame->sse_reg_save_offset = offset;
/* Va-arg area */
@@ -8431,10 +8425,7 @@ ix86_compute_frame_layout (struct ix86_frame *frame)
offset += frame->va_arg_size;
/* Align start of frame for local function. */
- frame->padding1 = ((offset + stack_alignment_needed - 1)
- & -stack_alignment_needed) - offset;
-
- offset += frame->padding1;
+ offset = (offset + stack_alignment_needed - 1) & -stack_alignment_needed;
/* Frame pointer points here. */
frame->frame_pointer_offset = offset;
@@ -8460,23 +8451,16 @@ ix86_compute_frame_layout (struct ix86_frame *frame)
or using alloca. */
if (!current_function_is_leaf || cfun->calls_alloca
|| ix86_current_function_calls_tls_descriptor)
- frame->padding2 = ((offset + preferred_alignment - 1)
- & -preferred_alignment) - offset;
- else
- frame->padding2 = 0;
-
- offset += frame->padding2;
+ offset = (offset + preferred_alignment - 1) & -preferred_alignment;
/* We've reached end of stack frame. */
frame->stack_pointer_offset = offset;
/* Size prologue needs to allocate. */
- frame->to_allocate =
- (size + frame->padding1 + frame->padding2
- + frame->outgoing_arguments_size + frame->va_arg_size);
+ to_allocate = offset - frame->sse_reg_save_offset;
- if ((!frame->to_allocate && frame->nregs <= 1)
- || (TARGET_64BIT && frame->to_allocate >= (HOST_WIDE_INT) 0x80000000))
+ if ((!to_allocate && frame->nregs <= 1)
+ || (TARGET_64BIT && to_allocate >= (HOST_WIDE_INT) 0x80000000))
frame->save_regs_using_mov = false;
if (ix86_using_red_zone ()
@@ -8484,7 +8468,7 @@ ix86_compute_frame_layout (struct ix86_frame *frame)
&& current_function_is_leaf
&& !ix86_current_function_calls_tls_descriptor)
{
- frame->red_zone_size = frame->to_allocate;
+ frame->red_zone_size = to_allocate;
if (frame->save_regs_using_mov)
frame->red_zone_size += frame->nregs * UNITS_PER_WORD;
if (frame->red_zone_size > RED_ZONE_SIZE - RED_ZONE_RESERVE)
@@ -8492,7 +8476,6 @@ ix86_compute_frame_layout (struct ix86_frame *frame)
}
else
frame->red_zone_size = 0;
- frame->to_allocate -= frame->red_zone_size;
frame->stack_pointer_offset -= frame->red_zone_size;
}
@@ -9597,16 +9580,13 @@ ix86_expand_prologue (void)
m->fs.realigned = true;
}
- allocate = frame.to_allocate + frame.nsseregs * 16 + frame.padding0;
-
if (!frame.save_regs_using_mov)
{
ix86_emit_save_regs ();
int_registers_saved = true;
gcc_assert (m->fs.sp_offset == frame.reg_save_offset);
}
- else
- allocate += frame.nregs * UNITS_PER_WORD;
+ allocate = frame.stack_pointer_offset - m->fs.sp_offset;
/* The stack has already been decremented by the instruction calling us
so we need to probe unconditionally to preserve the protection area. */
@@ -9992,11 +9972,12 @@ ix86_expand_epilogue (int style)
restore_regs_via_mov = true;
else if (TARGET_EPILOGUE_USING_MOVE
&& cfun->machine->use_fast_prologue_epilogue
- && (frame.nregs > 1 || (frame.to_allocate + frame.padding0) != 0))
+ && (frame.nregs > 1
+ || m->fs.sp_offset != frame.reg_save_offset))
restore_regs_via_mov = true;
else if (frame_pointer_needed
&& !frame.nregs
- && (frame.to_allocate + frame.padding0) != 0)
+ && m->fs.sp_offset != frame.reg_save_offset)
restore_regs_via_mov = true;
else if (frame_pointer_needed
&& TARGET_USE_LEAVE
--
1.7.2
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