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Propagate values through some wide Zero/Move operations. Among other things this allows us to optimize some kinds of array initialization. For example, the following code no longer requires a temporary be allocated on the stack. Instead it writes the values directly into the return value. func f(i uint32) [4]uint32 { return [4]uint32{i, i+1, i+2, i+3} } The return value is unnecessarily cleared but removing that is probably a task for dead store analysis (I think it needs to be able to match multiple Store ops to wide Zero ops). In order to reliably remove stack variables that are rendered unnecessary by these new rules I've added a new generic version of the unread autos elimination pass. These rules are triggered more than 5000 times when building and testing the standard library. Updates #15925 (fixes for arrays of up to 4 elements). Updates #24386 (fixes for up to 4 kept elements). Updates #24416. compilebench results: name old time/op new time/op delta Template 353ms ± 5% 359ms ± 3% ~ (p=0.143 n=10+10) Unicode 219ms ± 1% 217ms ± 4% ~ (p=0.740 n=7+10) GoTypes 1.26s ± 1% 1.26s ± 2% ~ (p=0.549 n=9+10) Compiler 6.00s ± 1% 6.08s ± 1% +1.42% (p=0.000 n=9+8) SSA 15.3s ± 2% 15.6s ± 1% +2.43% (p=0.000 n=10+10) Flate 237ms ± 2% 240ms ± 2% +1.31% (p=0.015 n=10+10) GoParser 285ms ± 1% 285ms ± 1% ~ (p=0.878 n=8+8) Reflect 797ms ± 3% 807ms ± 2% ~ (p=0.065 n=9+10) Tar 334ms ± 0% 335ms ± 4% ~ (p=0.460 n=8+10) XML 419ms ± 0% 423ms ± 1% +0.91% (p=0.001 n=7+9) StdCmd 46.0s ± 0% 46.4s ± 0% +0.85% (p=0.000 n=9+9) name old user-time/op new user-time/op delta Template 337ms ± 3% 346ms ± 5% ~ (p=0.053 n=9+10) Unicode 205ms ±10% 205ms ± 8% ~ (p=1.000 n=10+10) GoTypes 1.22s ± 2% 1.21s ± 3% ~ (p=0.436 n=10+10) Compiler 5.85s ± 1% 5.93s ± 0% +1.46% (p=0.000 n=10+8) SSA 14.9s ± 1% 15.3s ± 1% +2.62% (p=0.000 n=10+10) Flate 229ms ± 4% 228ms ± 6% ~ (p=0.796 n=10+10) GoParser 271ms ± 3% 275ms ± 4% ~ (p=0.165 n=10+10) Reflect 779ms ± 5% 775ms ± 2% ~ (p=0.971 n=10+10) Tar 317ms ± 4% 319ms ± 5% ~ (p=0.853 n=10+10) XML 404ms ± 4% 409ms ± 5% ~ (p=0.436 n=10+10) name old alloc/op new alloc/op delta Template 34.9MB ± 0% 35.0MB ± 0% +0.26% (p=0.000 n=10+10) Unicode 29.3MB ± 0% 29.3MB ± 0% +0.02% (p=0.000 n=10+10) GoTypes 115MB ± 0% 115MB ± 0% +0.30% (p=0.000 n=10+10) Compiler 519MB ± 0% 521MB ± 0% +0.30% (p=0.000 n=10+10) SSA 1.55GB ± 0% 1.57GB ± 0% +1.34% (p=0.000 n=10+9) Flate 24.1MB ± 0% 24.2MB ± 0% +0.10% (p=0.000 n=10+10) GoParser 28.1MB ± 0% 28.1MB ± 0% +0.07% (p=0.000 n=10+10) Reflect 78.7MB ± 0% 78.7MB ± 0% +0.03% (p=0.000 n=8+10) Tar 34.4MB ± 0% 34.5MB ± 0% +0.12% (p=0.000 n=10+10) XML 43.2MB ± 0% 43.2MB ± 0% +0.13% (p=0.000 n=10+10) name old allocs/op new allocs/op delta Template 330k ± 0% 330k ± 0% -0.01% (p=0.017 n=10+10) Unicode 337k ± 0% 337k ± 0% +0.01% (p=0.000 n=9+10) GoTypes 1.15M ± 0% 1.15M ± 0% +0.03% (p=0.000 n=10+10) Compiler 4.77M ± 0% 4.77M ± 0% +0.03% (p=0.000 n=9+10) SSA 12.5M ± 0% 12.6M ± 0% +1.16% (p=0.000 n=10+10) Flate 221k ± 0% 221k ± 0% +0.05% (p=0.000 n=9+10) GoParser 275k ± 0% 275k ± 0% +0.01% (p=0.014 n=10+9) Reflect 944k ± 0% 944k ± 0% -0.02% (p=0.000 n=10+10) Tar 324k ± 0% 323k ± 0% -0.12% (p=0.000 n=10+10) XML 384k ± 0% 384k ± 0% -0.01% (p=0.001 n=10+10) name old object-bytes new object-bytes delta Template 476kB ± 0% 476kB ± 0% -0.04% (p=0.000 n=10+10) Unicode 218kB ± 0% 218kB ± 0% ~ (all equal) GoTypes 1.58MB ± 0% 1.58MB ± 0% -0.04% (p=0.000 n=10+10) Compiler 6.25MB ± 0% 6.24MB ± 0% -0.09% (p=0.000 n=10+10) SSA 15.9MB ± 0% 16.1MB ± 0% +1.22% (p=0.000 n=10+10) Flate 304kB ± 0% 304kB ± 0% -0.13% (p=0.000 n=10+10) GoParser 370kB ± 0% 370kB ± 0% -0.00% (p=0.000 n=10+10) Reflect 1.27MB ± 0% 1.27MB ± 0% -0.12% (p=0.000 n=10+10) Tar 421kB ± 0% 419kB ± 0% -0.64% (p=0.000 n=10+10) XML 518kB ± 0% 517kB ± 0% -0.12% (p=0.000 n=10+10) name old export-bytes new export-bytes delta Template 16.7kB ± 0% 16.7kB ± 0% ~ (all equal) Unicode 6.52kB ± 0% 6.52kB ± 0% ~ (all equal) GoTypes 29.2kB ± 0% 29.2kB ± 0% ~ (all equal) Compiler 88.0kB ± 0% 88.0kB ± 0% ~ (all equal) SSA 109kB ± 0% 109kB ± 0% ~ (all equal) Flate 4.49kB ± 0% 4.49kB ± 0% ~ (all equal) GoParser 8.10kB ± 0% 8.10kB ± 0% ~ (all equal) Reflect 7.71kB ± 0% 7.71kB ± 0% ~ (all equal) Tar 9.15kB ± 0% 9.15kB ± 0% ~ (all equal) XML 12.3kB ± 0% 12.3kB ± 0% ~ (all equal) name old text-bytes new text-bytes delta HelloSize 676kB ± 0% 672kB ± 0% -0.59% (p=0.000 n=10+10) CmdGoSize 7.26MB ± 0% 7.24MB ± 0% -0.18% (p=0.000 n=10+10) name old data-bytes new data-bytes delta HelloSize 10.2kB ± 0% 10.2kB ± 0% ~ (all equal) CmdGoSize 248kB ± 0% 248kB ± 0% ~ (all equal) name old bss-bytes new bss-bytes delta HelloSize 125kB ± 0% 125kB ± 0% ~ (all equal) CmdGoSize 145kB ± 0% 145kB ± 0% ~ (all equal) name old exe-bytes new exe-bytes delta HelloSize 1.46MB ± 0% 1.45MB ± 0% -0.31% (p=0.000 n=10+10) CmdGoSize 14.7MB ± 0% 14.7MB ± 0% -0.17% (p=0.000 n=10+10) Change-Id: Ic72b0c189dd542f391e1c9ab88a76e9148dc4285 Reviewed-on: https://go-review.googlesource.com/106495 Run-TryBot: Michael Munday <mike.munday@ibm.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org> |
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.. | ||
arithmetic.go | ||
bitfield.go | ||
bits.go | ||
comparisons.go | ||
condmove.go | ||
copy.go | ||
floats.go | ||
issue22703.go | ||
mapaccess.go | ||
maps.go | ||
math.go | ||
mathbits.go | ||
memcombine.go | ||
README | ||
rotate.go | ||
slices.go | ||
stack.go | ||
strings.go | ||
structs.go |
// Copyright 2018 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. The codegen directory contains code generation tests for the gc compiler. - Introduction The test harness compiles Go code inside files in this directory and then matches the generated assembly (the output of `go tool compile -S`) against a set of regexps specified in comments that follow a special syntax (described below). The test driver is implemented as a step of the top-level test/run.go suite, called "asmcheck". The codegen tests run during all.bash, but can also be run in isolation by using $ ../bin/go run run.go -v codegen in the top-level test directory. The test harness compiles the tests with the same go toolchain that is used to run run.go. After writing tests for a newly added codegen transformation, it can be useful to first run the test harness with a toolchain from a released Go version (and verify that the new tests fail), and then re-runnig the tests using the devel toolchain. - Regexps comments syntax Instructions to match are specified inside plain comments that start with an architecture tag, followed by a colon and a quoted Go-style regexp to be matched. For example, the following test: func Sqrt(x float64) float64 { // amd64:"SQRTSD" // arm64:"FSQRTD" return math.Sqrt(x) } verifies that math.Sqrt calls are intrinsified to a SQRTSD instruction on amd64, and to a FSQRTD instruction on arm64. It is possible to put multiple architectures checks into the same line, as: // amd64:"SQRTSD" arm64:"FSQRTD" although this form should be avoided when doing so would make the regexps line excessively long and difficult to read. Comments that are on their own line will be matched against the first subsequent non-comment line. Inline comments are also supported; the regexp will be matched against the code found on the same line: func Sqrt(x float64) float64 { return math.Sqrt(x) // arm:"SQRTD" } It's possible to specify a comma-separated list of regexps to be matched. For example, the following test: func TZ8(n uint8) int { // amd64:"BSFQ","ORQ\t\\$256" return bits.TrailingZeros8(n) } verifies that the code generated for a bits.TrailingZeros8 call on amd64 contains both a "BSFQ" instruction and an "ORQ $256". Note how the ORQ regex includes a tab char (\t). In the Go assembly syntax, operands are separated from opcodes by a tabulation. Regexps can be quoted using either " or `. Special characters must be escaped accordingly. Both of these are accepted, and equivalent: // amd64:"ADDQ\t\\$3" // amd64:`ADDQ\t\$3` and they'll match this assembly line: ADDQ $3 Negative matches can be specified using a - before the quoted regexp. For example: func MoveSmall() { x := [...]byte{1, 2, 3, 4, 5, 6, 7} copy(x[1:], x[:]) // arm64:-".*memmove" } verifies that NO memmove call is present in the assembly generated for the copy() line. - Architecture specifiers There are three different ways to specify on which architecture a test should be run: * Specify only the architecture (eg: "amd64"). This indicates that the check should be run on all the supported architecture variants. For instance, arm checks will be run against all supported GOARM variations (5,6,7). * Specify both the architecture and a variant, separated by a slash (eg: "arm/7"). This means that the check will be run only on that specific variant. * Specify the operating system, the architecture and the variant, separated by slashes (eg: "plan9/386/sse2", "plan9/amd64/"). This is needed in the rare case that you need to do a codegen test affected by a specific operating system; by default, tests are compiled only targeting linux. - Remarks, and Caveats -- Write small test functions As a general guideline, test functions should be small, to avoid possible interactions between unrelated lines of code that may be introduced, for example, by the compiler's optimization passes. Any given line of Go code could get assigned more instructions that it may appear from reading the source. In particular, matching all MOV instructions should be avoided; the compiler may add them for unrelated reasons and this may render the test ineffective. -- Line matching logic Regexps are always matched from the start of the instructions line. This means, for example, that the "MULQ" regexp is equivalent to "^MULQ" (^ representing the start of the line), and it will NOT match the following assembly line: IMULQ $99, AX To force a match at any point of the line, ".*MULQ" should be used. For the same reason, a negative regexp like -"memmove" is not enough to make sure that no memmove call is included in the assembly. A memmove call looks like this: CALL runtime.memmove(SB) To make sure that the "memmove" symbol does not appear anywhere in the assembly, the negative regexp to be used is -".*memmove".