The SSA generic rewrite rules implement DeMorgan's laws but are
missing the closely related boolean absorption laws:
x & (x | y) == x
x | (x & y) == x
These are fundamental boolean algebra identities (see
https://en.wikipedia.org/wiki/Absorption_law) that hold for all
bit patterns, all widths, signed and unsigned. Both GCC and LLVM
recognize and optimize these patterns at -O2.
Add two generic rules covering all four widths (8, 16, 32, 64).
Commutativity of AND/OR is handled automatically by the rule
engine, so all argument orderings are matched.
The rules eliminate two redundant ALU instructions per occurrence
and fire on real code (defer bit-manipulation patterns in runtime,
testing, go/parser, and third-party packages).
Fixes#78632
Change-Id: Ib59e839081302ad1635e823309d8aec768c25dcf
GitHub-Last-Rev: 23f8296ece
GitHub-Pull-Request: golang/go#78634
Reviewed-on: https://go-review.googlesource.com/c/go/+/765580
Reviewed-by: Keith Randall <khr@google.com>
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Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
Replace \s with a space in backtick-quoted strings
Replace \\s with a space in double-quoted strings
Change-Id: I0c8b249bb12c2c8ca69e683e4bc6f27544fd6094
Reviewed-on: https://go-review.googlesource.com/c/go/+/760680
Auto-Submit: Keith Randall <khr@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Paul Murphy <paumurph@redhat.com>
Reviewed-by: Keith Randall <khr@google.com>
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A bunch of tests had broken yet undetected syntax errors
in their assembly output regexps. Things like mismatched quotes,
using ^ instead of - for negation, etc.
In addition, since CL 716060 using commas as separators between
regexps doesn't work, and ends up just silently dropping every
regexp after the comma.
Fix all these things, and add a test to make sure that we're not
silently dropping regexps on the floor.
After this CL I will do some cleanup to align with CL 716060, like
replacing commas and \s with spaces (which was the point of that CL,
but wasn't consistently rewritten everywhere).
Change-Id: I54f226120a311ead0c6c62eaf5d152ceed106034
Reviewed-on: https://go-review.googlesource.com/c/go/+/760521
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Paul Murphy <paumurph@redhat.com>
Auto-Submit: Keith Randall <khr@google.com>
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Theses test cases search for an AND that gets
optimized away after CL 760307.
Should help to fix riscv64 (coudn't check as
builders don't appear on https://build.golang.org/ )
and loong64 CI on master.
Change-Id: I57e4e5ab7d3003f239355137472585e46493d8dc
Reviewed-on: https://go-review.googlesource.com/c/go/+/760640
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Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
The prove pass removes superfluous bit masking. This was meant to
test the edge cases of the ppc64 folding rules which are exactly
the cases the prove pass now removes.
Fixes#78403
Change-Id: I45eeac58e01b42e19b8a06bb0d7af96c616ccbff
Reviewed-on: https://go-review.googlesource.com/c/go/+/760307
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Paul Murphy <paumurph@redhat.com>
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Ensure that loading the value of one is included and specify the actual
constants for various instructions. Avoid potential ambiguity with
instructions (e.g. use "AND " to avoid matching "ANDI").
Change-Id: I42707bd68fab9e12d984670e64a02ee93667f77c
Reviewed-on: https://go-review.googlesource.com/c/go/+/748920
Reviewed-by: Julian Zhu <julian.oerv@isrc.iscas.ac.cn>
Reviewed-by: David Chase <drchase@google.com>
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Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>
This commit adds two test functions, bitsOptXor1 and bitsOptXor2,
to verify that the compiler correctly optimizes certain bitwise
expression patterns in future CLs.
Change-Id: Idf5bd1ff8653f8fa218604d857639e063546d8e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/736540
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
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Also more consistently include commas after constants to increase
accuracy (i.e. "1," cannot inadvertantly match "10")
Change-Id: I480a73859d2e83354b8e9f94bc73c6563976d0e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/733460
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Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Use Go idiomatic function names, use a common prefix, attempt to
maintain some consistency, avoid naming functions based upon
machine specific instructions and combine a duplicate test that
likely exists due to this confusion.
Change-Id: I996e9efd7497821edef94c1997d4a310d9d79a71
Reviewed-on: https://go-review.googlesource.com/c/go/+/732200
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Auto-Submit: Joel Sing <joel@sing.id.au>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Change-Id: Iba4d3ded15d578e97a978780069e70a51a5e944b
Reviewed-on: https://go-review.googlesource.com/c/go/+/732180
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Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Joel Sing <joel@sing.id.au>
Separate patterns in asmcheck by spaces instead of commas.
Many patterns end in comma (like "MOV [$]123,") so separating
patterns by comma is not great; they're already quoted, so spaces are fine.
Also replace all tabs in the assembly lines with spaces before matching.
Finally, replace \$ or \\$ with [$] as the matching idiom.
The effect of all these is to make the patterns look like:
// amd64:"BSFQ" "ORQ [$]256"
instead of the old:
// amd64:"BSFQ","ORQ\t\\$256"
Update all tests as well.
Change-Id: Ia39febe5d7f67ba115846422789e11b185d5c807
Reviewed-on: https://go-review.googlesource.com/c/go/+/716060
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Reviewed-by: Alan Donovan <adonovan@google.com>
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In the loong64 instruction set, there is no NORI instruction,
so the immediate value in NORconst need to be stored in register
and then use the three-register NOR instruction.
Change-Id: I5ef697450619317218cb3ef47fc07e238bdc2139
Reviewed-on: https://go-review.googlesource.com/c/go/+/673836
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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Fold constant int16 addends for usages of math/bits.Add64(x,const,0)
on PPC64. This usage shows up in a few crypto implementations;
notably the go wrapper for CL 626176.
Change-Id: I6963163330487d04e0479b4fdac235f97bb96889
Reviewed-on: https://go-review.googlesource.com/c/go/+/625899
Reviewed-by: Cherry Mui <cherryyz@google.com>
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Auto-Submit: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
RLIWNM does not clear the upper 32 bits of the target register if
the mask wraps around (e.g 0xF000000F). Don't elide MOVWZreg for
such masks. All other usage clears the upper 32 bits.
Fixes#67844.
Change-Id: I11b89f1da9ae077624369bfe2bf25e9b7c9b79bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/590896
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@google.com>
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This commit is aimed at improving the readability and consistency
of the code base. Extraneous newline characters were present after
some return statements, creating unnecessary separation in the code.
Fixes#64610
Change-Id: Ic1b05bf11761c4dff22691c2f1c3755f66d341f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/548316
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
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Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Generate RLDIC[LR] instead of MOVD mask, Rx; AND Rx, Ry, Rz.
This helps reduce code size, and reduces the latency caused
by the constant load.
Similarly, for smaller-than-register values, truncate constants
which exceed the range of the value's type to avoid needing to
load a constant.
Change-Id: I6019684795eb8962d4fd6d9585d08b17c15e7d64
Reviewed-on: https://go-review.googlesource.com/c/go/+/515576
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Paul Murphy <murp@ibm.com>
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Reviewed-by: Cherry Mui <cherryyz@google.com>
Stop using BTSconst and friends when ORLconst can be used instead.
OR can be issued by more function units than BTS can, so it could
lead to better IPC. OR might take a few more bytes to encode, but
not a lot more.
Still use BTSconst for cases where the constant otherwise wouldn't
fit and would require a separate movabs instruction to materialize
the constant. This happens when setting bits 31-63 of 64-bit targets.
Add BTS-to-memory operations so we don't need to load/bts/store.
Fixes#61694
Change-Id: I00379608df8fb0167cb01466e97d11dec7c1596c
Reviewed-on: https://go-review.googlesource.com/c/go/+/515755
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
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(ANDCCconst [y] (MOV.*reg x)) should only be merged when zero
extending. Otherwise, sign bits are lost on negative values.
(ANDCCconst [0xFF] (MOVBreg x)) should be simplified to a zero
extension of x. Likewise for the MOVHreg variant.
Fixes#61297
Change-Id: I04e4fd7dc6a826e870681f37506620d48393698b
Reviewed-on: https://go-review.googlesource.com/c/go/+/508775
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Reviewed-by: Cherry Mui <cherryyz@google.com>
These operations (BT{S,R,C}{Q,L}modify) are quite a bit slower than
other ways of doing the same thing.
Without the BTxmodify operations, there are two fallback ways the compiler
performs these operations: AND/OR/XOR operations directly on memory, or
load-BTx-write sequences. The compiler kinda chooses one arbitrarily
depending on rewrite rule application order. Currently, it uses
load-BTx-write for the Const benchmarks and AND/OR/XOR directly to memory
for the non-Const benchmarks. TBD, someone might investigate which of
the two fallback strategies is really better. For now, they are both
better than BTx ops.
name old time/op new time/op delta
BitSet-8 1.09µs ± 2% 0.64µs ± 5% -41.60% (p=0.000 n=9+10)
BitClear-8 1.15µs ± 3% 0.68µs ± 6% -41.00% (p=0.000 n=10+10)
BitToggle-8 1.18µs ± 4% 0.73µs ± 2% -38.36% (p=0.000 n=10+8)
BitSetConst-8 37.0ns ± 7% 25.8ns ± 2% -30.24% (p=0.000 n=10+10)
BitClearConst-8 30.7ns ± 2% 25.0ns ±12% -18.46% (p=0.000 n=10+10)
BitToggleConst-8 36.9ns ± 1% 23.8ns ± 3% -35.46% (p=0.000 n=9+10)
Fixes#45790
Update #45242
Change-Id: Ie33a72dc139f261af82db15d446cd0855afb4e59
Reviewed-on: https://go-review.googlesource.com/c/go/+/318149
Trust: Keith Randall <khr@golang.org>
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Reviewed-by: Ben Shi <powerman1st@163.com>
Some codegen tests were written with the assumption that
arguments and results are in memory, and with a specific stack
layout. With the register ABI, the assumption is no longer true.
Adjust the tests to work with both cases.
- For tests expecting in memory arguments/results, change to use
global variables or memory-assigned argument/results.
- Allow more registers. E.g. some tests expecting register names
contain only letters (e.g. AX), but it can also contain numbers
(e.g. R10).
- Some instruction selection changes when operate on register vs.
memory, e.g. ADDQ vs. LEAQ, MOVB vs. MOVL. Accept both.
TODO: mathbits.go and memops.go still need fix.
Change-Id: Ic5932b4b5dd3f5d30ed078d296476b641420c4c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/309335
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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: 9a42bd29a5
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>
Some bit test instruction generation stopped triggering after
the change to addressing modes. I suspect this was just because
ANDQload was being generated before the rewrite rules could discover
the BTQ. Fix that by decomposing the ANDQload when it is surrounded
by a TESTQ (thus re-enabling the BTQ rules).
Fixes#44228
Change-Id: I489b4a5a7eb01c65fc8db0753f8cec54097cadb2
Reviewed-on: https://go-review.googlesource.com/c/go/+/291749
Trust: Keith Randall <khr@golang.org>
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Fixes#42445
Change-Id: I9653ef094dba2a1ac2e3daaa98279d10df17a2a1
Reviewed-on: https://go-review.googlesource.com/c/go/+/268257
Trust: Alberto Donizetti <alb.donizetti@gmail.com>
Trust: Martin Möhrmann <moehrmann@google.com>
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
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Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Optimize combinations of left and right shifts by a constant value
into a 'rotate then insert selected bits [into zero]' instruction.
Use the same instruction for contiguous masks since it has some
benefits over 'and immediate' (not restricted to 32-bits, does not
overwrite source register).
To keep the complexity of this change under control I've only
implemented 64 bit operations for now.
There are a lot more optimizations that can be done with this
instruction family. However, since their function overlaps with other
instructions we need to be somewhat careful not to break existing
optimization rules by creating optimization dead ends. This is
particularly true of the load/store merging rules which contain lots
of zero extensions and shifts.
This CL does interfere with the store merging rules when an operand
is shifted left before it is stored:
binary.BigEndian.PutUint64(b, x << 1)
This is unfortunate but it's not critical and somewhat complex so
I plan to fix that in a follow up CL.
file before after Δ %
addr2line 4117446 4117282 -164 -0.004%
api 4945184 4942752 -2432 -0.049%
asm 4998079 4991891 -6188 -0.124%
buildid 2685158 2684074 -1084 -0.040%
cgo 4553732 4553394 -338 -0.007%
compile 19294446 19245070 -49376 -0.256%
cover 4897105 4891319 -5786 -0.118%
dist 3544389 3542785 -1604 -0.045%
doc 3926795 3927617 +822 +0.021%
fix 3302958 3293868 -9090 -0.275%
link 6546274 6543456 -2818 -0.043%
nm 4102021 4100825 -1196 -0.029%
objdump 4542431 4548483 +6052 +0.133%
pack 2482465 2416389 -66076 -2.662%
pprof 13366541 13363915 -2626 -0.020%
test2json 2829007 2761515 -67492 -2.386%
trace 10216164 10219684 +3520 +0.034%
vet 6773956 6773572 -384 -0.006%
total 107124151 106917891 -206260 -0.193%
Change-Id: I7591cce41e06867ba10a745daae9333513062746
Reviewed-on: https://go-review.googlesource.com/c/go/+/233317
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Michael Munday <mike.munday@ibm.com>
This optimization works on any integer with exactly one bit set.
This is identical to being a power of two, except in the
most negative number. Use oneBit instead.
The rule now triggers in a few more places in std+cmd,
in packages encoding/asn1, crypto/elliptic, and
vendor/golang.org/x/crypto/cryptobyte.
This change obviates the need for CL 222479
by doing this optimization consistently in the compiler.
Change-Id: I983c6235290fdc634fda5e11b10f1f8ce041272f
Reviewed-on: https://go-review.googlesource.com/c/go/+/229124
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The assembly output for x & c == c, where c is power of 2:
MOVQ "".set+8(SP), AX
ANDQ $8, AX
CMPQ AX, $8
SETEQ "".~r2+24(SP)
With optimization using bitset:
MOVQ "".set+8(SP), AX
BTL $3, AX
SETCS "".~r2+24(SP)
output less than 1 instruction.
However, there is no speed improvement:
name old time/op new time/op delta
AllBitSet-8 0.35ns ± 0% 0.35ns ± 0% ~ (all equal)
Fixes#31904
Change-Id: I5dca4e410bf45716ed2145e3473979ec997e35d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/175957
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
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And delete them from asm_test.
Change-Id: I24f421b87e8cb4770c887a6dfd58eacd0088947d
Reviewed-on: https://go-review.googlesource.com/106056
Reviewed-by: Keith Randall <khr@golang.org>
The top-level test harness is modified to support a new kind
of test: "asmcheck". This is meant to replace asm_test.go
as an easier and more readable way to test code generation.
I've added a couple of codegen tests to get initial feedback
on the syntax. I've created them under a common "codegen"
subdirectory, so that it's easier to run them all with
"go run run.go -v codegen".
The asmcheck syntax allows to insert line comments that
can specify a regular expression to match in the assembly code,
for multiple architectures (the testsuite will automatically
build each testfile multiple times, one per mentioned architecture).
Negative matches are unsupported for now, so this cannot fully
replace asm_test yet.
Change-Id: Ifdbba389f01d55e63e73c99e5f5449e642101d55
Reviewed-on: https://go-review.googlesource.com/97355
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>
