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Hexagon (target/hexagon) Use QEMU decodetree (16-bit instructions)
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Section 10.3 of the Hexagon V73 Programmer's Reference Manual

A duplex is encoded as a 32-bit instruction with bits [15:14] set to 00.
The sub-instructions that comprise a duplex are encoded as 13-bit fields
in the duplex.

Create a decoder for each subinstruction class (a, l1, l2, s1, s2).

Extend gen_trans_funcs.py to handle all instructions rather than
filter by instruction class.

There is a g_assert_not_reached() in decode_insns() in decode.c to
verify we never try to use the old decoder on 16-bit instructions.

Signed-off-by: Taylor Simpson <ltaylorsimpson@gmail.com>
Reviewed-by: Brian Cain <bcain@quicinc.com>
Message-Id: <20240115221443.365287-3-ltaylorsimpson@gmail.com>
Signed-off-by: Brian Cain <bcain@quicinc.com>
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@taylorsimpson @androm3da
taylorsimpson authored and androm3da committed Jan 22, 2024
1 parent 1547a2d commit f6c0100
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Showing 5 changed files with 188 additions and 12 deletions.
1 change: 1 addition & 0 deletions target/hexagon/README
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Expand Up @@ -195,6 +195,7 @@ Step 1 is to run target/hexagon/gen_dectree_import.c to produce
Step 2 is to import iset.py into target/hexagon/gen_decodetree.py to produce
<BUILD_DIR>/target/hexagon/normal_decode_generated
<BUILD_DIR>/target/hexagon/hvx_decode_generated
<BUILD_DIR>/target/hexagon/subinsn_*_decode_generated
Step 3 is to process the above files with QEMU's decodetree.py to produce
<BUILD_DIR>/target/hexagon/decode_*_generated.c.inc
Step 4 is to import iset.py into target/hexagon/gen_trans_funcs.py to produce
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85 changes: 85 additions & 0 deletions target/hexagon/decode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,7 @@ static int decode_mapped_reg_##NAME(DisasContext *ctx, int x) \
}
DECODE_MAPPED(R_16)
DECODE_MAPPED(R_8)
DECODE_MAPPED(R__8)

/* Helper function for decodetree_trans_funcs_generated.c.inc */
static int shift_left(DisasContext *ctx, int x, int n, int immno)
Expand All @@ -77,6 +78,13 @@ static int shift_left(DisasContext *ctx, int x, int n, int immno)
#include "decode_normal_generated.c.inc"
#include "decode_hvx_generated.c.inc"

/* Include the generated decoder for 16 bit insn */
#include "decode_subinsn_a_generated.c.inc"
#include "decode_subinsn_l1_generated.c.inc"
#include "decode_subinsn_l2_generated.c.inc"
#include "decode_subinsn_s1_generated.c.inc"
#include "decode_subinsn_s2_generated.c.inc"

/* Include the generated helpers for the decoder */
#include "decodetree_trans_funcs_generated.c.inc"

Expand Down Expand Up @@ -790,6 +798,63 @@ decode_insns_tablewalk(Insn *insn, const DectreeTable *table,
}
}

/*
* Section 10.3 of the Hexagon V73 Programmer's Reference Manual
*
* A duplex is encoded as a 32-bit instruction with bits [15:14] set to 00.
* The sub-instructions that comprise a duplex are encoded as 13-bit fields
* in the duplex.
*
* Per table 10-4, the 4-bit duplex iclass is encoded in bits 31:29, 13
*/
static uint32_t get_duplex_iclass(uint32_t encoding)
{
uint32_t iclass = extract32(encoding, 13, 1);
iclass = deposit32(iclass, 1, 3, extract32(encoding, 29, 3));
return iclass;
}

/*
* Per table 10-5, the duplex ICLASS field values that specify the group of
* each sub-instruction in a duplex
*
* This table points to the decode instruction for each entry in the table
*/
typedef bool (*subinsn_decode_func)(DisasContext *ctx, uint16_t insn);
typedef struct {
subinsn_decode_func decode_slot0_subinsn;
subinsn_decode_func decode_slot1_subinsn;
} subinsn_decode_groups;

static const subinsn_decode_groups decode_groups[16] = {
[0x0] = { decode_subinsn_l1, decode_subinsn_l1 },
[0x1] = { decode_subinsn_l2, decode_subinsn_l1 },
[0x2] = { decode_subinsn_l2, decode_subinsn_l2 },
[0x3] = { decode_subinsn_a, decode_subinsn_a },
[0x4] = { decode_subinsn_l1, decode_subinsn_a },
[0x5] = { decode_subinsn_l2, decode_subinsn_a },
[0x6] = { decode_subinsn_s1, decode_subinsn_a },
[0x7] = { decode_subinsn_s2, decode_subinsn_a },
[0x8] = { decode_subinsn_s1, decode_subinsn_l1 },
[0x9] = { decode_subinsn_s1, decode_subinsn_l2 },
[0xa] = { decode_subinsn_s1, decode_subinsn_s1 },
[0xb] = { decode_subinsn_s2, decode_subinsn_s1 },
[0xc] = { decode_subinsn_s2, decode_subinsn_l1 },
[0xd] = { decode_subinsn_s2, decode_subinsn_l2 },
[0xe] = { decode_subinsn_s2, decode_subinsn_s2 },
[0xf] = { NULL, NULL }, /* Reserved */
};

static uint16_t get_slot0_subinsn(uint32_t encoding)
{
return extract32(encoding, 0, 13);
}

static uint16_t get_slot1_subinsn(uint32_t encoding)
{
return extract32(encoding, 16, 13);
}

static unsigned int
decode_insns(DisasContext *ctx, Insn *insn, uint32_t encoding)
{
Expand All @@ -805,8 +870,28 @@ decode_insns(DisasContext *ctx, Insn *insn, uint32_t encoding)
table = &dectree_table_DECODE_ROOT_32;
g_assert_not_reached();
} else {
uint32_t iclass = get_duplex_iclass(encoding);
unsigned int slot0_subinsn = get_slot0_subinsn(encoding);
unsigned int slot1_subinsn = get_slot1_subinsn(encoding);
subinsn_decode_func decode_slot0_subinsn =
decode_groups[iclass].decode_slot0_subinsn;
subinsn_decode_func decode_slot1_subinsn =
decode_groups[iclass].decode_slot1_subinsn;

/* The slot1 subinsn needs to be in the packet first */
if (decode_slot1_subinsn(ctx, slot1_subinsn)) {
insn->generate = opcode_genptr[insn->opcode];
insn->iclass = iclass_bits(encoding);
ctx->insn = ++insn;
if (decode_slot0_subinsn(ctx, slot0_subinsn)) {
insn->generate = opcode_genptr[insn->opcode];
insn->iclass = iclass_bits(encoding);
return 2;
}
}
/* start with EE table - duplex instructions */
table = &dectree_table_DECODE_ROOT_EE;
g_assert_not_reached();
}
return decode_insns_tablewalk(insn, table, encoding);
}
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12 changes: 10 additions & 2 deletions target/hexagon/gen_decodetree.py
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Original file line number Diff line number Diff line change
Expand Up @@ -96,8 +96,10 @@ def skip_tag(tag, class_to_decode):
## A2_add ..................-.....---..... @A2_add
##
def gen_decodetree_file(f, class_to_decode):
is_subinsn = class_to_decode.startswith("SUBINSN_")
f.write(f"## DO NOT MODIFY - This file is generated by {sys.argv[0]}\n\n")
f.write("%PP\t14:2\n\n")
if not is_subinsn:
f.write("%PP\t14:2\n\n")
for tag in sorted(encs.keys(), key=iset.tags.index):
if skip_tag(tag, class_to_decode):
continue
Expand All @@ -108,6 +110,10 @@ def gen_decodetree_file(f, class_to_decode):
f"## {tag}:\t{enc_str}\n"
"##\n")

# The subinstructions come with a 13-bit encoding, but
# decodetree.py needs 16 bits
if is_subinsn:
enc_str = "---" + enc_str

regs = ordered_unique(regre.findall(iset.iset[tag]["syntax"]))
imms = ordered_unique(immre.findall(iset.iset[tag]["syntax"]))
Expand Down Expand Up @@ -174,7 +180,9 @@ def gen_decodetree_file(f, class_to_decode):
imm_letter = "i" if imm_type.islower() else "I"
f.write(f" {imm_type}{imm_letter}=%{tag}_{imm_type}{imm_letter}")

f.write(" %PP\n")
if not is_subinsn:
f.write(" %PP")
f.write("\n")

# Replace the 0s and 1s with .
enc_str = enc_str.replace("0", ".").replace("1", ".")
Expand Down
12 changes: 2 additions & 10 deletions target/hexagon/gen_trans_funcs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,11 +40,6 @@ def ordered_unique(l):
return sorted(set(l), key=l.index)


def skip_tag(tag, classes):
enc_class = iset.iset[tag]["enc_class"]
return enc_class not in classes


def code_fmt(txt):
return textwrap.indent(textwrap.dedent(txt), " ")

Expand Down Expand Up @@ -76,12 +71,9 @@ def mark_which_imm_extended(f, tag):
## return true;
## }
##
def gen_trans_funcs(f, classes):
def gen_trans_funcs(f):
f.write(f"/* DO NOT MODIFY - This file is generated by {sys.argv[0]} */\n\n")
for tag in sorted(encs.keys(), key=iset.tags.index):
if skip_tag(tag, classes):
continue

regs = ordered_unique(regre.findall(iset.iset[tag]["syntax"]))
imms = ordered_unique(immre.findall(iset.iset[tag]["syntax"]))

Expand Down Expand Up @@ -129,4 +121,4 @@ def gen_trans_funcs(f, classes):
if __name__ == "__main__":
hex_common.read_semantics_file(sys.argv[1])
with open(sys.argv[2], "w") as f:
gen_trans_funcs(f, { "NORMAL", "EXT_mmvec" })
gen_trans_funcs(f)
90 changes: 90 additions & 0 deletions target/hexagon/meson.build
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Original file line number Diff line number Diff line change
Expand Up @@ -154,6 +154,51 @@ hvx_decode_generated = custom_target(
)
hexagon_ss.add(hvx_decode_generated)

subinsn_a_decode_generated = custom_target(
'subinsn_a_decode_generated',
output: 'subinsn_a_decode_generated',
depends: [iset_py, semantics_generated],
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files('gen_decodetree.py'), semantics_generated, 'SUBINSN_A', '@OUTPUT@'],
)
hexagon_ss.add(subinsn_a_decode_generated)

subinsn_l1_decode_generated = custom_target(
'subinsn_l1_decode_generated',
output: 'subinsn_l1_decode_generated',
depends: [iset_py, semantics_generated],
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files('gen_decodetree.py'), semantics_generated, 'SUBINSN_L1', '@OUTPUT@'],
)
hexagon_ss.add(subinsn_l1_decode_generated)

subinsn_l2_decode_generated = custom_target(
'subinsn_l2_decode_generated',
output: 'subinsn_l2_decode_generated',
depends: [iset_py, semantics_generated],
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files('gen_decodetree.py'), semantics_generated, 'SUBINSN_L2', '@OUTPUT@'],
)
hexagon_ss.add(subinsn_l2_decode_generated)

subinsn_s1_decode_generated = custom_target(
'subinsn_s1_decode_generated',
output: 'subinsn_s1_decode_generated',
depends: [iset_py, semantics_generated],
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files('gen_decodetree.py'), semantics_generated, 'SUBINSN_S1', '@OUTPUT@'],
)
hexagon_ss.add(subinsn_s1_decode_generated)

subinsn_s2_decode_generated = custom_target(
'subinsn_s2_decode_generated',
output: 'subinsn_s2_decode_generated',
depends: [iset_py, semantics_generated],
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files('gen_decodetree.py'), semantics_generated, 'SUBINSN_S2', '@OUTPUT@'],
)
hexagon_ss.add(subinsn_s2_decode_generated)

#
# Run the QEMU decodetree.py script to produce the instruction decoder
#
Expand All @@ -176,6 +221,51 @@ decode_hvx_generated = custom_target(
)
hexagon_ss.add(decode_hvx_generated)

decode_subinsn_a_generated = custom_target(
'decode_subinsn_a_generated.c.inc',
output: 'decode_subinsn_a_generated.c.inc',
input: subinsn_a_decode_generated,
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files(decodetree_py), subinsn_a_decode_generated, ['--static-decode=decode_subinsn_a', '--insnwidth=16'], '-o', '@OUTPUT@'],
)
hexagon_ss.add(decode_subinsn_a_generated)

decode_subinsn_l1_generated = custom_target(
'decode_subinsn_l1_generated.c.inc',
output: 'decode_subinsn_l1_generated.c.inc',
input: subinsn_l1_decode_generated,
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files(decodetree_py), subinsn_l1_decode_generated, ['--static-decode=decode_subinsn_l1', '--insnwidth=16'], '-o', '@OUTPUT@'],
)
hexagon_ss.add(decode_subinsn_l1_generated)

decode_subinsn_l2_generated = custom_target(
'decode_subinsn_l2_generated.c.inc',
output: 'decode_subinsn_l2_generated.c.inc',
input: subinsn_l2_decode_generated,
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files(decodetree_py), subinsn_l2_decode_generated, ['--static-decode=decode_subinsn_l2', '--insnwidth=16'], '-o', '@OUTPUT@'],
)
hexagon_ss.add(decode_subinsn_l2_generated)

decode_subinsn_s1_generated = custom_target(
'decode_subinsn_s1_generated.c.inc',
output: 'decode_subinsn_s1_generated.c.inc',
input: subinsn_s1_decode_generated,
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files(decodetree_py), subinsn_s1_decode_generated, ['--static-decode=decode_subinsn_s1', '--insnwidth=16'], '-o', '@OUTPUT@'],
)
hexagon_ss.add(decode_subinsn_s1_generated)

decode_subinsn_s2_generated = custom_target(
'decode_subinsn_s2_generated.c.inc',
output: 'decode_subinsn_s2_generated.c.inc',
input: subinsn_s2_decode_generated,
env: {'PYTHONPATH': meson.current_build_dir()},
command: [python, files(decodetree_py), subinsn_s2_decode_generated, ['--static-decode=decode_subinsn_s2', '--insnwidth=16'], '-o', '@OUTPUT@'],
)
hexagon_ss.add(decode_subinsn_s2_generated)

#
# Generate the trans_* functions that the decoder will use
#
Expand Down

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