Remove the special casing for len/cap and rely on the posets.
After removing the special logic, I ran `go build -gcflags='-d
ssa/prove/debug=2' all` to verify my results. During this, I found 2
common cases where the old implicit unsigned->signed domain conversion
made proving a branch possible that shouldn't be strictly possible and
added these.
The 2 cases are shifting a non-negative signed integer and unsigned
comparisons that happen with arguments that fits entirely inside the
unsigned argument
Change-Id: Ic88049ff69efc5602fc15f5dad02028e704f5483
Reviewed-on: https://go-review.googlesource.com/c/go/+/679155
Reviewed-by: Mark Freeman <mark@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
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(StringLen (StringMake _ x)) == x, just like the rules we
currently have for slices.
This helps propagate string length knowledge to places which need it.
Change-Id: Ifdcf6d1f2d430c1c4bbac32e0ea74c188eae998e
Reviewed-on: https://go-review.googlesource.com/c/go/+/682777
Reviewed-by: Daniel Morsing <daniel.morsing@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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I've split this into it's own CL to make git bisect more effective.
Change-Id: I436ff21a3e2362b3924de25a458534eb9947e013
Reviewed-on: https://go-review.googlesource.com/c/go/+/685821
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I've split this into it's own CL to make git bisect more effective.
Change-Id: Ib2c6dbc82fb04f50f2d17fbe6626c9fc322fb478
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I've split this into it's own CL to make git bisect more effective.
Change-Id: I3fbb42ec7d29169a29f7f55ef2c188317512f532
Reviewed-on: https://go-review.googlesource.com/c/go/+/685819
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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I've split this into it's own CL to make git bisect more effective.
Change-Id: Iaab5f0bd2ad51e86ced8c6b8fbd371eb75eeef14
Reviewed-on: https://go-review.googlesource.com/c/go/+/685815
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prove.go used to make my editor and precomit checks very unhappy.
Change-Id: I25f7ffa2191480bc1b4f91fa91ccf3e4768045fa
Reviewed-on: https://go-review.googlesource.com/c/go/+/685818
Reviewed-by: Carlos Amedee <carlos@golang.org>
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-N+1 <= x % N <= N-1
This is useful for cases like:
func setBit(b []byte, i int) {
b[i/8] |= 1<<(i%8)
}
The shift does not need protection against larger-than-7 cases.
(It does still need protection against <0 cases.)
Change-Id: Idf83101386af538548bfeb6e2928cea855610ce2
Reviewed-on: https://go-review.googlesource.com/c/go/+/672995
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Use the existing Value method to make it a bit shorter.
Change-Id: I47c4328b5241ab48b3490a04a3d93d4428f7b88c
Reviewed-on: https://go-review.googlesource.com/c/go/+/642735
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For: #70156
Change-Id: Ie39a88130f27b4b210ddbcf396cc0ddd2713d58b
Reviewed-on: https://go-review.googlesource.com/c/go/+/624855
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Fixes: #70156
Change-Id: I2e5dc2a39a8e54ec5f18c5f9d1644208cffb2e9a
Reviewed-on: https://go-review.googlesource.com/c/go/+/624695
Auto-Submit: Keith Randall <khr@golang.org>
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If there is a phi that is computing the minimum of its two inputs,
then we know the result of the phi is smaller than or equal to both
of its inputs. Similarly for maxiumum (although max seems less useful).
This pattern happens for the case
n := copy(a, b)
n is the minimum of len(a) and len(b), so with this optimization we
know both n <= len(a) and n <= len(b). That extra information is
helpful for subsequent slicing of a or b.
Fixes#16833
Change-Id: Ib4238fd1edae0f2940f62a5516a6b363bbe7928c
Reviewed-on: https://go-review.googlesource.com/c/go/+/622240
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Now that we're bootstrapping from a toolchain that has min/max builtins.
Update #64751
Change-Id: I63eedf3cca00f56f62ca092949cb2dc61db03361
Reviewed-on: https://go-review.googlesource.com/c/go/+/610355
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: I2e4d74a86faa95321e847a061e06c3efff7f20df
Reviewed-on: https://go-review.googlesource.com/c/go/+/605775
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I was not sure this was correct so I exhaustively checked all possibilities:
https://go.dev/play/p/hjmCLm4Iagzhttps://go.dev/play/p/R9RuRGKwCbN
Change-Id: I85f053df825a4d77f978de42f8a1fcaf4b881def
Reviewed-on: https://go-review.googlesource.com/c/go/+/605696
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Change-Id: I419faa781db085b98ea25008ca127d0317fb34e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/605695
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I didn't implemented negative limits since prove is most useful for BCE which
should never be negative in the first place.
Change-Id: I302ee462cdc20bd4edff0618f7e49ff66fc2a007
Reviewed-on: https://go-review.googlesource.com/c/go/+/605136
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Change-Id: Id522bde5bba627d9cdc8c3d8e907bdc168e5b13c
Reviewed-on: https://go-review.googlesource.com/c/go/+/605157
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addLocalFacts loop already ft.update which sets up limits correctly, but doing this in flowLimit help us since other values might depend on this limit.
Updates #68857
We could improve this further:
- remove mod alltogheter when we can prove a < b.
- we could do more adhoc computation in flowLimit to set umax and umin tighter
Change-Id: I5184913577b6a51a07cb53a6e6b73552a982de0b
Reviewed-on: https://go-review.googlesource.com/c/go/+/605156
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Change-Id: I6902c405cab7bd573f6a721a6ca7c783713ea39a
Reviewed-on: https://go-review.googlesource.com/c/go/+/604456
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This help to optimize code like this:
func f(buckets *[512]bucket, v value) {
a, b := v.computeSomething()
// assume a and b are proved < 512
b := &buckets[a ^ b] // pick a random bucket
b.store(v)
}
Change-Id: I1acf702f5a8137f9ded49081b4703922879b0288
Reviewed-on: https://go-review.googlesource.com/c/go/+/604455
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See the cases above all of theses are implemented (except XOR which has a blank case with comments).
Change-Id: I9e2994490dac89e86ba70c1abeb1af1cbcf032e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/604416
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y := bits.TrailingZeros(x)
if y > bits.Len(x.umax)-1 {
then must always be true 1 << y > x.umax which is impossible
}
Change-Id: Iab4fce1c2ef828bee3a8a4a977cbadb5f9333136
Reviewed-on: https://go-review.googlesource.com/c/go/+/603996
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Change-Id: Ie3c7e5eaba6a9a29389018625c4b784d07c6f173
Reviewed-on: https://go-review.googlesource.com/c/go/+/603537
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Get rid of TODO in prove pass.
We currently avoid marking shifts of constants as bounded, where
bounded means we don't have to worry about <0 or >=bitwidth shifts.
We do this because it causes different rule applications during lowering
which cause some codegen tests to fail.
Add some new rules which ensure that we get the right final instruction
sequence regardless of the ordering. Then we can remove this special case.
Change-Id: I4e962d4f09992b42ab47e123de5ded3b8b8fb205
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Local facts can get us to unsatisfiable because there is an
unconditional panic in the block. That shouldn't declare the whole
block as unreachable, because we do still need to enter it to get
that panic.
Fixes#68816
Change-Id: I9220edb46089690702d2eb61d112815c7ac91f16
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I think I introduced #68809 when rewriting the prove pass, by
introducing an off-by-one error here:
https://go-review.googlesource.com/c/go/+/599096/5/src/cmd/compile/internal/ssa/prove.go
lines 872-874.
The min++ is already handled in one of the two following cases with
the (r&eq==0) condition. Move the min++ to just the other case.
Fixes#68809
Change-Id: Iffae99e29219c94aaf584cd7ae247289fa604a00
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We don't need noLimit checks in a bunch of places.
Also simplify folding of provable constant results.
At this point in the CL stack, compilebench reports no performance
changes. The only thing of note is that binaries got a bit smaller.
name old text-bytes new text-bytes delta
HelloSize 960kB ± 0% 952kB ± 0% -0.83% (p=0.000 n=10+10)
CmdGoSize 12.3MB ± 0% 12.1MB ± 0% -1.53% (p=0.000 n=10+10)
Change-Id: Id4be75eec0f8c93f2f3b93a8521ce2278ee2ee2c
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Move some code from when we learn that we take a branch, to when
we learn that a boolean is true or false. It is more consistent
this way (and may lead to a few more cases where we can derive
useful relations).
Change-Id: Iea7b2d6740e10c9c71c4b1546881f501da81cd21
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The constant lattice for these types is pretty simple.
We no longer need the old-style facts table, as the ordering
table now has all that information.
Change-Id: If0e118c27a4de8e9bfd727b78942185c2eb50c4b
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Handles a lot more cases where constant ranges can eliminate
various (mostly bounds failure) paths.
Fixes#66826Fixes#66692Fixes#48213
Update #57959
TODO: remove constant logic from poset code, no longer needed.
Change-Id: Id196436fcd8a0c84c7d59c04f93bd92e26a0fd7e
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Here begins a pretty major rewrite of the prove pass. The fundamental
observation is that although keeping facts about relations between
two SSA values could use O(n^2) space, keeping facts about relations
between an SSA value and constants needs only O(n) space. We can just
keep track of min/max for every SSA value at little cost.
Redo the limit table to just keep track of limits for all SSA values.
Use just a slice instead of a map. It may use more space (but still
just O(n) space), but accesses are a lot faster. And with the cache
in the compiler, that space will be reused quickly.
This is part of my planning to add lots more constant limits in the
prove pass.
Change-Id: Ie36819fad5631a8b79c3630fe0e819521796551a
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I wrote theses checks because I got bad panics on some innocent functions,
turns out I was working around #63955 but I was not aware of that at the time.
The proper fix was included in CL 539977 this is now doing nothing.
Change-Id: I89329329933527b6f3cb817dc1e039a38f58da9a
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Fixes#61629
This reduce the pressure on regalloc because then the loop only keep alive
one value (the iterator) instead of the iterator and the upper bound since
the comparison now acts against an immediate, often zero which can be skipped.
This optimize things like:
for i := 0; i < n; i++ {
Or a range over a slice where the index is not used:
for _, v := range someSlice {
Or the new range over int from #61405:
for range n {
It is hit in 975 unique places while doing ./make.bash.
Change-Id: I5facff8b267a0b60ea3c1b9a58c4d74cdb38f03f
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Fix spelling errors discovered using https://github.com/codespell-project/codespell. Errors in data files and vendored packages are ignored.
Change-Id: I83c7818222f2eea69afbd270c15b7897678131dc
GitHub-Last-Rev: 3491615b1b
GitHub-Pull-Request: golang/go#60758
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For now, only apply the rule if either of arguments are constants. That
would catch a lot of real user code, without slowing down the compiler
with code generated for string comparison (experience in CL 410336).
Updates #57959Fixes#45928
Change-Id: Ie2e830d6d0d71cda3947818b22c2775bd94f7971
Reviewed-on: https://go-review.googlesource.com/c/go/+/483359
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Currently, the prove pass can get knowledge from some specific logic
operators only before the CFG is explored, which means that the bounds
information of the branch will be ignored.
This CL updates the facts table by the logic operators in every
branch. Combined with the branch information, this will be helpful for
BCE in some circumstances.
Fixes#57243
Change-Id: I0bd164f1b47804ccfc37879abe9788740b016fd5
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