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re PR middle-end/34548 (GCC generates too many alignment adds for alloca)

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PR 34548

	* function.h (struct rtl_data): Add max_dynamic_stack_alignment.
	* cfgexpand.c (gimple_expand_cfg): Initialise it.
	* explow.c (allocate_dynamic_stack_space): Set it.  Simplify
	alignment requirements given the known alignment of dynamic_offset.
	* function.c (instantiate_virtual_regs): Align dtnamic_offset.

From-SVN: r190051
This commit is contained in:
Richard Henderson 2012-08-01 13:41:16 -07:00 committed by Richard Henderson
parent 91f8035e9b
commit 70ce4a25c4
5 changed files with 40 additions and 38 deletions
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9
gcc/ChangeLog
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@ -1,3 +1,12 @@
2012-08-01 Richard Henderson <rth@redhat.com>
PR middle-end/34548
* function.h (struct rtl_data): Add max_dynamic_stack_alignment.
* cfgexpand.c (gimple_expand_cfg): Initialise it.
* explow.c (allocate_dynamic_stack_space): Set it. Simplify
alignment requirements given the known alignment of dynamic_offset.
* function.c (instantiate_virtual_regs): Align dtnamic_offset.
2012-08-01 Richard Henderson <rth@redhat.com>
* expmed.h (NUM_MODE_PARTIAL_INT): New.

1
gcc/cfgexpand.c
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@ -4363,6 +4363,7 @@ gimple_expand_cfg (void)
crtl->max_used_stack_slot_alignment = STACK_BOUNDARY;
crtl->stack_alignment_estimated = 0;
crtl->preferred_stack_boundary = STACK_BOUNDARY;
crtl->max_dynamic_stack_alignment = 0;
cfun->cfg->max_jumptable_ents = 0;
/* Resovle the function section. Some targets, like ARM EABI rely on knowledge

57
gcc/explow.c
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@ -1173,7 +1173,6 @@ allocate_dynamic_stack_space (rtx size, unsigned size_align,
{
HOST_WIDE_INT stack_usage_size = -1;
rtx final_label, final_target, target;
unsigned extra_align = 0;
bool must_align;
/* If we're asking for zero bytes, it doesn't matter what we point
@ -1237,58 +1236,40 @@ allocate_dynamic_stack_space (rtx size, unsigned size_align,
else if (size_align < BITS_PER_UNIT)
size_align = BITS_PER_UNIT;
/* We can't attempt to minimize alignment necessary, because we don't
know the final value of preferred_stack_boundary yet while executing
this code. */
if (crtl->preferred_stack_boundary < PREFERRED_STACK_BOUNDARY)
crtl->preferred_stack_boundary = PREFERRED_STACK_BOUNDARY;
/* We will need to ensure that the address we return is aligned to
REQUIRED_ALIGN. If STACK_DYNAMIC_OFFSET is defined, we don't
always know its final value at this point in the compilation (it
might depend on the size of the outgoing parameter lists, for
example), so we must align the value to be returned in that case.
(Note that STACK_DYNAMIC_OFFSET will have a default nonzero value if
STACK_POINTER_OFFSET or ACCUMULATE_OUTGOING_ARGS are defined).
We must also do an alignment operation on the returned value if
the stack pointer alignment is less strict than REQUIRED_ALIGN.
If we have to align, we must leave space in SIZE for the hole
that might result from the alignment operation. */
must_align = (crtl->preferred_stack_boundary < required_align);
if (must_align)
REQUIRED_ALIGN. If that alignment is no larger than
PREFERRED_STACK_BOUNDARY, we can handle everything without an
explicit alignment. */
if (required_align <= PREFERRED_STACK_BOUNDARY)
{
if (required_align > PREFERRED_STACK_BOUNDARY)
extra_align = PREFERRED_STACK_BOUNDARY;
else if (required_align > STACK_BOUNDARY)
extra_align = STACK_BOUNDARY;
else
extra_align = BITS_PER_UNIT;
if (crtl->preferred_stack_boundary < required_align)
crtl->preferred_stack_boundary = required_align;
if (crtl->max_dynamic_stack_alignment < required_align)
crtl->max_dynamic_stack_alignment = required_align;
must_align = false;
}
/* ??? STACK_POINTER_OFFSET is always defined now. */
#if defined (STACK_DYNAMIC_OFFSET) || defined (STACK_POINTER_OFFSET)
must_align = true;
extra_align = BITS_PER_UNIT;
#endif
if (must_align)
else
{
unsigned extra = (required_align - extra_align) / BITS_PER_UNIT;
unsigned extra, extra_align;
crtl->preferred_stack_boundary = PREFERRED_STACK_BOUNDARY;
crtl->max_dynamic_stack_alignment = PREFERRED_STACK_BOUNDARY;
extra_align = PREFERRED_STACK_BOUNDARY;
extra = (required_align - extra_align) / BITS_PER_UNIT;
size = plus_constant (Pmode, size, extra);
size = force_operand (size, NULL_RTX);
if (flag_stack_usage_info)
stack_usage_size += extra;
if (extra && size_align > extra_align)
size_align = extra_align;
must_align = true;
}
/* Round the size to a multiple of the required stack alignment.
Since the stack if presumed to be rounded before this allocation,
Since the stack is presumed to be rounded before this allocation,
this will maintain the required alignment.
If the stack grows downward, we could save an insn by subtracting

7
gcc/function.c
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@ -1892,7 +1892,14 @@ instantiate_virtual_regs (void)
/* Compute the offsets to use for this function. */
in_arg_offset = FIRST_PARM_OFFSET (current_function_decl);
var_offset = STARTING_FRAME_OFFSET;
dynamic_offset = STACK_DYNAMIC_OFFSET (current_function_decl);
if (crtl->max_dynamic_stack_alignment)
{
int align = crtl->max_dynamic_stack_alignment / BITS_PER_UNIT;
dynamic_offset = (dynamic_offset + align - 1) & -align;
}
out_arg_offset = STACK_POINTER_OFFSET;
#ifdef FRAME_POINTER_CFA_OFFSET
cfa_offset = FRAME_POINTER_CFA_OFFSET (current_function_decl);

4
gcc/function.h
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@ -347,6 +347,10 @@ struct GTY(()) rtl_data {
local stack. */
unsigned int stack_alignment_estimated;
/* The (capped) maximum alignment of dynamic stack space, and thus the
required alignment of STACK_DYNAMIC_OFFSET. */
unsigned int max_dynamic_stack_alignment;
/* For reorg. */
/* If some insns can be deferred to the delay slots of the epilogue, the