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xtensa: constantsynth: Make try to find shorter instruction

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This patch allows the constant synthesis to choose shorter instruction
if possible.

    /* example */
    int test(void) {
      return 128 << 8;
    }

    ;; before
    test:
	movi	a2, 0x100
	addmi	a2, a2, 0x7f00
	ret.n

    ;; after
    test:
	movi.n	a2, 1
	slli	a2, a2, 15
	ret.n

When the Code Density Option is configured, the latter is one byte smaller
than the former.

gcc/ChangeLog:

	* config/xtensa/xtensa.cc (xtensa_emit_constantsynth): Remove.
	(xtensa_constantsynth_2insn): Change to try all three synthetic
	methods and to use the one that fits the immediate value of
	the seed into a Narrow Move Immediate instruction "MOVI.N"
	when the Code Density Option is configured.
This commit is contained in:
Takayuki 'January June' Suwa
2022-07-15 19:50:52 +09:00
committed by Max Filippov
parent bdc7b765f8
commit 1884f89782
1 changed files with 29 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files
gcc/config/xtensa/xtensa.cc
+29 -29
View File
@@ -1035,35 +1035,35 @@ xtensa_split_operand_pair (rtx operands[4], machine_mode mode)
load-immediate / arithmetic ones, instead of a L32R instruction
(plus a constant in litpool). */
static void
xtensa_emit_constantsynth (rtx dst, enum rtx_code code,
HOST_WIDE_INT imm0, HOST_WIDE_INT imm1,
rtx (*gen_op)(rtx, HOST_WIDE_INT),
HOST_WIDE_INT imm2)
{
gcc_assert (REG_P (dst));
emit_move_insn (dst, GEN_INT (imm0));
emit_move_insn (dst, gen_rtx_fmt_ee (code, SImode,
dst, GEN_INT (imm1)));
if (gen_op)
emit_move_insn (dst, gen_op (dst, imm2));
}
static int
xtensa_constantsynth_2insn (rtx dst, HOST_WIDE_INT srcval,
rtx (*gen_op)(rtx, HOST_WIDE_INT),
HOST_WIDE_INT op_imm)
{
int shift = exact_log2 (srcval + 1);
HOST_WIDE_INT imm = INT_MAX;
rtx x = NULL_RTX;
int shift;
gcc_assert (REG_P (dst));
shift = exact_log2 (srcval + 1);
if (IN_RANGE (shift, 1, 31))
{
xtensa_emit_constantsynth (dst, LSHIFTRT, -1, 32 - shift,
gen_op, op_imm);
return 1;
imm = -1;
x = gen_lshrsi3 (dst, dst, GEN_INT (32 - shift));
}
if (IN_RANGE (srcval, (-2048 - 32768), (2047 + 32512)))
shift = ctz_hwi (srcval);
if ((!x || (TARGET_DENSITY && ! IN_RANGE (imm, -32, 95)))
&& xtensa_simm12b (srcval >> shift))
{
imm = srcval >> shift;
x = gen_ashlsi3 (dst, dst, GEN_INT (shift));
}
if ((!x || (TARGET_DENSITY && ! IN_RANGE (imm, -32, 95)))
&& IN_RANGE (srcval, (-2048 - 32768), (2047 + 32512)))
{
HOST_WIDE_INT imm0, imm1;
@@ -1076,19 +1076,19 @@ xtensa_constantsynth_2insn (rtx dst, HOST_WIDE_INT srcval,
imm0 = srcval - imm1;
if (TARGET_DENSITY && imm1 < 32512 && IN_RANGE (imm0, 224, 255))
imm0 -= 256, imm1 += 256;
xtensa_emit_constantsynth (dst, PLUS, imm0, imm1, gen_op, op_imm);
return 1;
imm = imm0;
x = gen_addsi3 (dst, dst, GEN_INT (imm1));
}
shift = ctz_hwi (srcval);
if (xtensa_simm12b (srcval >> shift))
{
xtensa_emit_constantsynth (dst, ASHIFT, srcval >> shift, shift,
gen_op, op_imm);
return 1;
}
if (!x)
return 0;
return 0;
emit_move_insn (dst, GEN_INT (imm));
emit_insn (x);
if (gen_op)
emit_move_insn (dst, gen_op (dst, op_imm));
return 1;
}
static rtx