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359f44910f
Under certain circumstances, the existing rules for bit operations can
produce code that writes beyond its intended bounds. For example,
consider the following code:
func repro(b []byte, addr, bit int32) {
_ = b[3]
v := uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24 | 1<<(bit&31)
b[0] = byte(v)
b[1] = byte(v >> 8)
b[2] = byte(v >> 16)
b[3] = byte(v >> 24)
}
Roughly speaking:
1. The expression `1 << (bit & 31)` is rewritten into `(SHLL 1 bit)`
2. The expression `uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 |
uint32(b[3])<<24` is rewritten into `(MOVLload &b[0])`
3. The statements `b[0] = byte(v) ... b[3] = byte(v >> 24)` are
rewritten into `(MOVLstore &b[0], v)`
4. `(ORL (SHLL 1, bit) (MOVLload &b[0]))` is rewritten into
`(BTSL (MOVLload &b[0]) bit)`. This is a valid transformation because
the destination is a register: in this case, the bit offset is masked
by the number of bits in the destination register. This is identical
to the masking performed by `SHL`.
5. `(MOVLstore &b[0] (BTSL (MOVLload &b[0]) bit))` is rewritten into
`(BTSLmodify &b[0] bit)`. This is an invalid transformation because
the destination is memory: in this case, the bit offset is not
masked, and the chosen instruction may write outside its intended
32-bit location.
These changes fix the invalid rewrite performed in step (5) by
explicitly maksing the bit offset operand to `BT(S|R|C)(L|Q)modify`. In
the example above, the adjusted rules produce
`(BTSLmodify &b[0] (ANDLconst [31] bit))` in step (5).
These changes also add several new rules to rewrite bit sets, toggles,
and clears that are rooted at `(OR|XOR|AND)(L|Q)modify` operators into
appropriate `BT(S|R|C)(L|Q)modify` operators. These rules catch cases
where `MOV(L|Q)store ((OR|XOR|AND)(L|Q) ...)` is rewritten to
`(OR|XOR|AND)(L|Q)modify` before the `(OR|XOR|AND)(L|Q) ...` can be
rewritten to `BT(S|R|C)(L|Q) ...`.
Overall, compilecmp reports small improvements in code size on
darwin/amd64 when the changes to the compiler itself are exlcuded:
file before after Δ %
runtime.s 536464 536412 -52 -0.010%
bytes.s 32629 32593 -36 -0.110%
strings.s 44565 44529 -36 -0.081%
os/signal.s 7967 7959 -8 -0.100%
cmd/vendor/golang.org/x/sys/unix.s 81686 81678 -8 -0.010%
math/big.s 188235 188253 +18 +0.010%
cmd/link/internal/loader.s 89295 89056 -239 -0.268%
cmd/link/internal/ld.s 633551 633232 -319 -0.050%
cmd/link/internal/arm.s 18934 18928 -6 -0.032%
cmd/link/internal/arm64.s 31814 31801 -13 -0.041%
cmd/link/internal/riscv64.s 7347 7345 -2 -0.027%
cmd/compile/internal/ssa.s 4029173 4033066 +3893 +0.097%
total 21298280 21301472 +3192 +0.015%
Change-Id: I2e560548b515865129e1724e150e30540e9d29ce
GitHub-Last-Rev: 9a42bd29a55b3917651aecab6932074df96535ae
GitHub-Pull-Request: golang/go#45242
Reviewed-on: https://go-review.googlesource.com/c/go/+/304869
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Josh Bleecher Snyder <josharian@gmail.com>
370 lines
6.2 KiB
Go
370 lines
6.2 KiB
Go
// asmcheck
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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package codegen
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/************************************
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* 64-bit instructions
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************************************/
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func bitcheck64_constleft(a uint64) (n int) {
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// amd64:"BTQ\t[$]63"
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if a&(1<<63) != 0 {
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return 1
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}
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// amd64:"BTQ\t[$]60"
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if a&(1<<60) != 0 {
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return 1
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}
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// amd64:"BTL\t[$]0"
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if a&(1<<0) != 0 {
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return 1
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}
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return 0
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}
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func bitcheck64_constright(a [8]uint64) (n int) {
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// amd64:"BTQ\t[$]63"
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if (a[0]>>63)&1 != 0 {
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return 1
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}
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// amd64:"BTQ\t[$]63"
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if a[1]>>63 != 0 {
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return 1
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}
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// amd64:"BTQ\t[$]63"
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if a[2]>>63 == 0 {
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return 1
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}
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// amd64:"BTQ\t[$]60"
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if (a[3]>>60)&1 == 0 {
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return 1
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}
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// amd64:"BTL\t[$]1"
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if (a[4]>>1)&1 == 0 {
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return 1
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}
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// amd64:"BTL\t[$]0"
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if (a[5]>>0)&1 == 0 {
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return 1
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}
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// amd64:"BTL\t[$]7"
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if (a[6]>>5)&4 == 0 {
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return 1
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}
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return 0
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}
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func bitcheck64_var(a, b uint64) (n int) {
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// amd64:"BTQ"
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if a&(1<<(b&63)) != 0 {
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return 1
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}
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// amd64:"BTQ",-"BT.\t[$]0"
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if (b>>(a&63))&1 != 0 {
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return 1
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}
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return 0
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}
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func bitcheck64_mask(a uint64) (n int) {
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// amd64:"BTQ\t[$]63"
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if a&0x8000000000000000 != 0 {
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return 1
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}
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// amd64:"BTQ\t[$]59"
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if a&0x800000000000000 != 0 {
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return 1
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}
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// amd64:"BTL\t[$]0"
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if a&0x1 != 0 {
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return 1
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}
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return 0
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}
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func biton64(a, b uint64) (n uint64) {
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// amd64:"BTSQ"
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n += b | (1 << (a & 63))
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// amd64:"BTSQ\t[$]63"
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n += a | (1 << 63)
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// amd64:"BTSQ\t[$]60"
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n += a | (1 << 60)
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// amd64:"ORQ\t[$]1"
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n += a | (1 << 0)
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return n
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}
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func bitoff64(a, b uint64) (n uint64) {
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// amd64:"BTRQ"
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n += b &^ (1 << (a & 63))
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// amd64:"BTRQ\t[$]63"
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n += a &^ (1 << 63)
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// amd64:"BTRQ\t[$]60"
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n += a &^ (1 << 60)
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// amd64:"ANDQ\t[$]-2"
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n += a &^ (1 << 0)
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return n
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}
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func bitcompl64(a, b uint64) (n uint64) {
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// amd64:"BTCQ"
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n += b ^ (1 << (a & 63))
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// amd64:"BTCQ\t[$]63"
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n += a ^ (1 << 63)
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// amd64:"BTCQ\t[$]60"
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n += a ^ (1 << 60)
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// amd64:"XORQ\t[$]1"
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n += a ^ (1 << 0)
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return n
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}
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/************************************
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* 32-bit instructions
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************************************/
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func bitcheck32_constleft(a uint32) (n int) {
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// amd64:"BTL\t[$]31"
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if a&(1<<31) != 0 {
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return 1
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}
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// amd64:"BTL\t[$]28"
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if a&(1<<28) != 0 {
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return 1
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}
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// amd64:"BTL\t[$]0"
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if a&(1<<0) != 0 {
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return 1
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}
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return 0
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}
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func bitcheck32_constright(a [8]uint32) (n int) {
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// amd64:"BTL\t[$]31"
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if (a[0]>>31)&1 != 0 {
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return 1
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}
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// amd64:"BTL\t[$]31"
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if a[1]>>31 != 0 {
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return 1
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}
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// amd64:"BTL\t[$]31"
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if a[2]>>31 == 0 {
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return 1
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}
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// amd64:"BTL\t[$]28"
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if (a[3]>>28)&1 == 0 {
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return 1
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}
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// amd64:"BTL\t[$]1"
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if (a[4]>>1)&1 == 0 {
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return 1
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}
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// amd64:"BTL\t[$]0"
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if (a[5]>>0)&1 == 0 {
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return 1
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}
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// amd64:"BTL\t[$]7"
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if (a[6]>>5)&4 == 0 {
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return 1
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}
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return 0
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}
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func bitcheck32_var(a, b uint32) (n int) {
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// amd64:"BTL"
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if a&(1<<(b&31)) != 0 {
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return 1
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}
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// amd64:"BTL",-"BT.\t[$]0"
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if (b>>(a&31))&1 != 0 {
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return 1
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}
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return 0
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}
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func bitcheck32_mask(a uint32) (n int) {
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// amd64:"BTL\t[$]31"
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if a&0x80000000 != 0 {
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return 1
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}
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// amd64:"BTL\t[$]27"
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if a&0x8000000 != 0 {
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return 1
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}
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// amd64:"BTL\t[$]0"
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if a&0x1 != 0 {
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return 1
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}
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return 0
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}
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func biton32(a, b uint32) (n uint32) {
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// amd64:"BTSL"
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n += b | (1 << (a & 31))
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// amd64:"BTSL\t[$]31"
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n += a | (1 << 31)
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// amd64:"BTSL\t[$]28"
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n += a | (1 << 28)
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// amd64:"ORL\t[$]1"
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n += a | (1 << 0)
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return n
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}
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func bitoff32(a, b uint32) (n uint32) {
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// amd64:"BTRL"
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n += b &^ (1 << (a & 31))
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// amd64:"BTRL\t[$]31"
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n += a &^ (1 << 31)
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// amd64:"BTRL\t[$]28"
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n += a &^ (1 << 28)
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// amd64:"ANDL\t[$]-2"
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n += a &^ (1 << 0)
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return n
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}
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func bitcompl32(a, b uint32) (n uint32) {
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// amd64:"BTCL"
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n += b ^ (1 << (a & 31))
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// amd64:"BTCL\t[$]31"
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n += a ^ (1 << 31)
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// amd64:"BTCL\t[$]28"
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n += a ^ (1 << 28)
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// amd64:"XORL\t[$]1"
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n += a ^ (1 << 0)
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return n
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}
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// check direct operation on memory with constant and shifted constant sources
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func bitOpOnMem(a []uint32, b, c, d uint32) {
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// amd64:`ANDL\s[$]200,\s\([A-Z]+\)`
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a[0] &= 200
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// amd64:`ORL\s[$]220,\s4\([A-Z]+\)`
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a[1] |= 220
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// amd64:`XORL\s[$]240,\s8\([A-Z]+\)`
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a[2] ^= 240
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// amd64:`BTRL\s[$]15,\s12\([A-Z]+\)`,-`ANDL`
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a[3] &= 0xffff7fff
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// amd64:`BTSL\s[$]14,\s16\([A-Z]+\)`,-`ORL`
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a[4] |= 0x4000
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// amd64:`BTCL\s[$]13,\s20\([A-Z]+\)`,-`XORL`
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a[5] ^= 0x2000
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// amd64:`BTRL\s[A-Z]+,\s24\([A-Z]+\)`
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a[6] &^= 1 << (b & 31)
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// amd64:`BTSL\s[A-Z]+,\s28\([A-Z]+\)`
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a[7] |= 1 << (c & 31)
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// amd64:`BTCL\s[A-Z]+,\s32\([A-Z]+\)`
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a[8] ^= 1 << (d & 31)
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}
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func bitcheckMostNegative(b uint8) bool {
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// amd64:"TESTB"
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return b&0x80 == 0x80
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}
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// Check AND masking on arm64 (Issue #19857)
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func and_mask_1(a uint64) uint64 {
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// arm64:`AND\t`
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return a & ((1 << 63) - 1)
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}
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func and_mask_2(a uint64) uint64 {
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// arm64:`AND\t`
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return a & (1 << 63)
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}
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func and_mask_3(a, b uint32) (uint32, uint32) {
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// arm/7:`BIC`,-`AND`
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a &= 0xffffaaaa
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// arm/7:`BFC`,-`AND`,-`BIC`
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b &= 0xffc003ff
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return a, b
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}
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// Check generation of arm64 BIC/EON/ORN instructions
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func op_bic(x, y uint32) uint32 {
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// arm64:`BIC\t`,-`AND`
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return x &^ y
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}
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func op_eon(x, y, z uint32, a []uint32, n, m uint64) uint64 {
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// arm64:`EON\t`,-`EOR`,-`MVN`
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a[0] = x ^ (y ^ 0xffffffff)
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// arm64:`EON\t`,-`EOR`,-`MVN`
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a[1] = ^(y ^ z)
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// arm64:`EON\t`,-`XOR`
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a[2] = x ^ ^z
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// arm64:`EON\t`,-`EOR`,-`MVN`
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return n ^ (m ^ 0xffffffffffffffff)
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}
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func op_orn(x, y uint32) uint32 {
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// arm64:`ORN\t`,-`ORR`
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return x | ^y
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}
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// check bitsets
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func bitSetPowerOf2Test(x int) bool {
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// amd64:"BTL\t[$]3"
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return x&8 == 8
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}
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func bitSetTest(x int) bool {
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// amd64:"ANDQ\t[$]9, AX"
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// amd64:"CMPQ\tAX, [$]9"
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return x&9 == 9
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}
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// mask contiguous one bits
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func cont1Mask64U(x uint64) uint64 {
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// s390x:"RISBGZ\t[$]16, [$]47, [$]0,"
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return x & 0x0000ffffffff0000
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}
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// mask contiguous zero bits
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func cont0Mask64U(x uint64) uint64 {
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// s390x:"RISBGZ\t[$]48, [$]15, [$]0,"
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return x & 0xffff00000000ffff
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}
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func issue44228a(a []int64, i int) bool {
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// amd64: "BTQ", -"SHL"
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return a[i>>6]&(1<<(i&63)) != 0
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}
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func issue44228b(a []int32, i int) bool {
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// amd64: "BTL", -"SHL"
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return a[i>>5]&(1<<(i&31)) != 0
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}
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