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xtensa: Optimize stack frame adjustment more

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This patch introduces a convenient helper function for integer immediate
addition with scratch register as needed, that splits and emits either
up to two ADDI/ADDMI machine instructions or an addition by register
following an integer immediate load (which may later be transformed by
constantsynth).

By using the helper function, it makes stack frame adjustment logic
simplified and instruction count less in some cases.

gcc/ChangeLog:

	* config/xtensa/xtensa.cc
	(xtensa_split_imm_two_addends, xtensa_emit_add_imm):
	New helper functions.
	(xtensa_set_return_address, xtensa_output_mi_thunk):
	Change to use the helper function.
	(xtensa_emit_adjust_stack_ptr): Ditto.
	And also change to try reusing the content of scratch register
	A9 if the register is not modified in the function body.
This commit is contained in:
Takayuki 'January June' Suwa 2023-01-07 11:55:11 +09:00 committed by Max Filippov
parent 2d2edf1080
commit b095a1db48
1 changed files with 106 additions and 45 deletions
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151
gcc/config/xtensa/xtensa.cc
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@ -104,6 +104,7 @@ struct GTY(()) machine_function
bool frame_laid_out;
bool epilogue_done;
bool inhibit_logues_a1_adjusts;
rtx last_logues_a9_content;
};
/* Vector, indexed by hard register number, which contains 1 for a
@ -2518,6 +2519,86 @@ xtensa_split_DI_reg_imm (rtx *operands)
}
/* Try to split an integer value into what are suitable for two consecutive
immediate addition instructions, ADDI or ADDMI. */
static bool
xtensa_split_imm_two_addends (HOST_WIDE_INT imm, HOST_WIDE_INT v[2])
{
HOST_WIDE_INT v0, v1;
if (imm < -32768)
v0 = -32768, v1 = imm + 32768;
else if (imm > 32512)
v0 = 32512, v1 = imm - 32512;
else if (TARGET_DENSITY && xtensa_simm12b (imm))
/* A pair of MOVI(.N) and ADD.N is one or two bytes less than two
immediate additions if TARGET_DENSITY. */
return false;
else
v0 = (imm + 128) & ~255L, v1 = imm - v0;
if (xtensa_simm8 (v1) || xtensa_simm8x256 (v1))
{
v[0] = v0, v[1] = v1;
return true;
}
return false;
}
/* Helper function for integer immediate addition with scratch register
as needed, that splits and emits either up to two ADDI/ADDMI machine
instructions or an addition by register following an integer immediate
load (which may later be transformed by constantsynth).
If 'scratch' is NULL_RTX but still needed, a new pseudo-register will
be allocated. Thus, after the reload/LRA pass, the specified scratch
register must be a hard one. */
static bool
xtensa_emit_add_imm (rtx dst, rtx src, HOST_WIDE_INT imm, rtx scratch,
bool need_note)
{
bool retval = false;
HOST_WIDE_INT v[2];
rtx_insn *insn;
if (imm == 0)
return false;
if (xtensa_simm8 (imm) || xtensa_simm8x256 (imm))
insn = emit_insn (gen_addsi3 (dst, src, GEN_INT (imm)));
else if (xtensa_split_imm_two_addends (imm, v))
{
if (!scratch)
scratch = gen_reg_rtx (SImode);
emit_insn (gen_addsi3 (scratch, src, GEN_INT (v[0])));
insn = emit_insn (gen_addsi3 (dst, scratch, GEN_INT (v[1])));
}
else
{
if (scratch)
emit_move_insn (scratch, GEN_INT (imm));
else
scratch = force_reg (SImode, GEN_INT (imm));
retval = true;
insn = emit_insn (gen_addsi3 (dst, src, scratch));
}
if (need_note)
{
rtx note_rtx = gen_rtx_SET (dst, plus_constant (Pmode, src, imm));
RTX_FRAME_RELATED_P (insn) = 1;
add_reg_note (insn, REG_FRAME_RELATED_EXPR, note_rtx);
}
return retval;
}
/* Implement TARGET_CANNOT_FORCE_CONST_MEM. */
static bool
@ -3245,41 +3326,33 @@ xtensa_initial_elimination_offset (int from, int to ATTRIBUTE_UNUSED)
static void
xtensa_emit_adjust_stack_ptr (HOST_WIDE_INT offset, int flags)
{
rtx src, scratch;
rtx_insn *insn;
rtx ptr = (flags & ADJUST_SP_FRAME_PTR) ? hard_frame_pointer_rtx
: stack_pointer_rtx;
if (cfun->machine->inhibit_logues_a1_adjusts)
return;
if (xtensa_simm8 (offset)
|| xtensa_simm8x256 (offset))
insn = emit_insn (gen_addsi3 (stack_pointer_rtx, ptr, GEN_INT (offset)));
else
{
rtx tmp_reg = gen_rtx_REG (Pmode, A9_REG);
src = (flags & ADJUST_SP_FRAME_PTR)
? hard_frame_pointer_rtx : stack_pointer_rtx;
scratch = gen_rtx_REG (Pmode, A9_REG);
if (offset < 0)
if (df && DF_REG_DEF_COUNT (A9_REG) == 0
&& cfun->machine->last_logues_a9_content
&& -INTVAL (cfun->machine->last_logues_a9_content) == offset)
{
insn = emit_insn (gen_subsi3 (stack_pointer_rtx, src, scratch));
if (flags & ADJUST_SP_NEED_NOTE)
{
emit_move_insn (tmp_reg, GEN_INT (-offset));
insn = emit_insn (gen_subsi3 (stack_pointer_rtx, ptr, tmp_reg));
}
else
{
emit_move_insn (tmp_reg, GEN_INT (offset));
insn = emit_insn (gen_addsi3 (stack_pointer_rtx, ptr, tmp_reg));
rtx note_rtx = gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, src, offset));
RTX_FRAME_RELATED_P (insn) = 1;
add_reg_note (insn, REG_FRAME_RELATED_EXPR, note_rtx);
}
}
if (flags & ADJUST_SP_NEED_NOTE)
{
rtx note_rtx = gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
offset));
RTX_FRAME_RELATED_P (insn) = 1;
add_reg_note (insn, REG_FRAME_RELATED_EXPR, note_rtx);
}
else if (xtensa_emit_add_imm (stack_pointer_rtx, src, offset, scratch,
(flags & ADJUST_SP_NEED_NOTE)))
cfun->machine->last_logues_a9_content = GEN_INT (offset);
}
/* minimum frame = reg save area (4 words) plus static chain (1 word)
@ -3307,8 +3380,9 @@ xtensa_expand_prologue (void)
/* Use a8 as a temporary since a0-a7 may be live. */
rtx tmp_reg = gen_rtx_REG (Pmode, A8_REG);
emit_insn (gen_entry (GEN_INT (MIN_FRAME_SIZE)));
emit_move_insn (tmp_reg, GEN_INT (total_size - MIN_FRAME_SIZE));
emit_insn (gen_subsi3 (tmp_reg, stack_pointer_rtx, tmp_reg));
xtensa_emit_add_imm (tmp_reg, stack_pointer_rtx,
MIN_FRAME_SIZE - total_size,
tmp_reg, false);
insn = emit_insn (gen_movsi (stack_pointer_rtx, tmp_reg));
}
}
@ -3540,8 +3614,8 @@ xtensa_set_return_address (rtx address, rtx scratch)
if (total_size > 1024)
{
emit_move_insn (scratch, GEN_INT (total_size - UNITS_PER_WORD));
emit_insn (gen_addsi3 (scratch, frame, scratch));
xtensa_emit_add_imm (scratch, frame, total_size - UNITS_PER_WORD,
scratch, false);
a0_addr = scratch;
}
@ -5101,15 +5175,7 @@ xtensa_output_mi_thunk (FILE *file, tree thunk ATTRIBUTE_UNUSED,
this_rtx = gen_rtx_REG (Pmode, A0_REG + this_reg_no);
if (delta)
{
if (xtensa_simm8 (delta))
emit_insn (gen_addsi3 (this_rtx, this_rtx, GEN_INT (delta)));
else
{
emit_move_insn (temp0, GEN_INT (delta));
emit_insn (gen_addsi3 (this_rtx, this_rtx, temp0));
}
}
xtensa_emit_add_imm (this_rtx, this_rtx, delta, temp0, false);
if (vcall_offset)
{
@ -5119,13 +5185,8 @@ xtensa_output_mi_thunk (FILE *file, tree thunk ATTRIBUTE_UNUSED,
emit_move_insn (temp0, gen_rtx_MEM (Pmode, this_rtx));
if (xtensa_uimm8x4 (vcall_offset))
addr = plus_constant (Pmode, temp0, vcall_offset);
else if (xtensa_simm8 (vcall_offset))
emit_insn (gen_addsi3 (temp1, temp0, GEN_INT (vcall_offset)));
else
{
emit_move_insn (temp1, GEN_INT (vcall_offset));
emit_insn (gen_addsi3 (temp1, temp0, temp1));
}
xtensa_emit_add_imm (temp1, temp0, vcall_offset, temp1, false);
emit_move_insn (temp1, gen_rtx_MEM (Pmode, addr));
emit_insn (gen_add2_insn (this_rtx, temp1));
}