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fix literal-pow to return the right type when the base is -1 #53736

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oscardssmith
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fixes #53735.

@oscardssmith oscardssmith added maths Mathematical functions bugfix This change fixes an existing bug backport 1.10 Change should be backported to the 1.10 release backport 1.11 Change should be backported to release-1.11 labels Mar 14, 2024
base/intfuncs.jl Outdated Show resolved Hide resolved
@inline literal_pow(::typeof(^), x::HWNumber, ::Val{-1}) = inv(x)
@inline literal_pow(::typeof(^), x::HWNumber, ::Val{-2}) = (i=inv(x); i*i)
@inline function literal_pow(::typeof(^), x::HWNumber, ::Val{-1})
if x == -one(x)
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This change introduces even more type instability, now depending on the value of the x argument.

Other question: why special-case -1 and not 1?

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the reason to specialize only on -1 is that inv(x) often has a different type than x, but x*x generally is ok. what is a fade where this version is type unstable? unitful?

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I meant depending on the first argument: typeof ((-1)^-1) == Int, while typeof(1^-1) == Float64)

inv(x)
end
@inline function literal_pow(::typeof(^), x::HWNumber, ::Val{-2})
if x == -one(x)
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See previous comment on line 373

@@ -379,7 +390,9 @@ const HWNumber = Union{HWReal, Complex{<:HWReal}, Rational{<:HWReal}}
# for other types, define x^-n as inv(x)^n so that negative literal powers can
# be computed in a type-stable way even for e.g. integers.
@inline function literal_pow(f::typeof(^), x, ::Val{p}) where {p}
if p < 0
if x == -one(x)
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See previous comment on line 373

Co-authored-by: Max Horn <max@quendi.de>
@KristofferC KristofferC mentioned this pull request Mar 15, 2024
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@KristofferC
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Ref #53735 (comment)

KristofferC added a commit that referenced this pull request Mar 17, 2024
Backported PRs:
- [x] #39071 <!-- Add a lazy `logrange` function and `LogRange` type -->
- [x] #51802 <!-- Allow AnnotatedStrings in log messages -->
- [x] #53369 <!-- Orthogonalize re-indexing for FastSubArrays -->
- [x] #48050 <!-- improve `--heap-size-hint` arg handling -->
- [x] #53482 <!-- add IR encoding for EnterNode -->
- [x] #53499 <!-- Avoid compiler warning about redefining jl_globalref_t
-->
- [x] #53507 <!-- update staled `Core.Compiler.Effects` documentation
-->
- [x] #53408 <!-- task splitting: change additive accumulation to
multiplicative -->
- [x] #53523 <!-- add back an alias for `check_top_bit` -->
- [x] #53377 <!-- add _readdirx for returning more object info gathered
during dir scan -->
- [x] #53525 <!-- fix InteractiveUtils call in Base.runtests on failure
-->
- [x] #53540 <!-- use more efficient `_readdirx` for tab completion -->
- [x] #53545 <!-- use `_readdirx` for `walkdir` -->
- [x] #53551 <!-- revert "Add @create_log_macro for making custom styled
logging macros (#52196)" -->
- [x] #53554 <!-- Always return a value in 1-d circshift! of
abstractarray.jl -->
- [x] #53424 <!-- yet more atomics & cache-line fixes on work-stealing
queue -->
- [x] #53571 <!-- Update Documenter to v1.3 for inventory writing -->
- [x] #53403 <!-- Move parallel precompilation to Base -->
- [x] #53589 <!-- add back `unsafe_convert` to pointer for arrays -->
- [x] #53596 <!-- build: remove extra .a file -->
- [x] #53606 <!-- fix error path in `precompilepkgs` -->
- [x] #53004 <!-- Unexport with, at_with, and ScopedValue from Base -->
- [x] #53629 <!-- typo fix in scoped values docs -->
- [x] #53630 <!-- sroa: Fix incorrect scope counting -->
- [x] #53598 <!-- Use Base parallel precompilation to build stdlibs -->
- [x] #53649 <!-- precompilepkgs: package in boths deps and weakdeps are
in fact only weak -->
- [x] #53671 <!-- Fix bootstrap Base precompile in cross compile
configuration -->
- [x] #52125 <!-- Load Pkg if not already to reinstate missing package
add prompt -->
- [x] #53602 <!-- Handle zero on arrays of unions of number types and
missings -->
- [x] #53516 <!-- permit NamedTuple{<:Any, Union{}} to be created -->
- [x] #53643 <!-- Bump CSL to 1.1.1 to fix libgomp bug -->
- [x] #53679 <!-- move precompile workload back from Base -->
- [x] #53663 <!-- add isassigned methods for reinterpretarray -->
- [x] #53662 <!-- [REPL] fix incorrectly cleared line after completions
accepted -->
- [x] #53611 <!-- Linalg: matprod_dest for Diagonal and adjvec -->
- [x] #53659 <!-- fix #52025, re-allow all implicit pointer casts in
cconvert for Array -->
- [x] #53631 <!-- LAPACK: validate input parameters to throw informative
errors -->
- [x] #53628 <!-- Make some improvements to the Scoped Values
documentation. -->
- [x] #53655 <!-- Change tbaa of ptr_phi to tbaa_value  -->
- [x] #53391 <!-- Default to the medium code model in x86 linux -->
- [x] #53699 <!-- Move `isexecutable, isreadable, iswritable` to
`filesystem.jl` -->
- [x] #41232 <!-- Fix linear indexing for ReshapedArray if the parent
has offset axes -->
- [x] #53527 <!-- Enable analyzegc checks for try catch and fix found
issues -->
- [x] #52092 
- [x] #53682 <!-- Increase build precompilation -->
- [x] #53720 
- [x] #53553 <!-- typeintersect: fix `UnionAll` unaliasing bug caused by
innervars. -->

Contains multiple commits, manual intervention needed:
- [ ] #53305 <!-- Propagate inbounds in isassigned with CartesianIndex
indices -->

Non-merged PRs with backport label:
- [ ] #53736 <!-- fix literal-pow to return the right type when the base
is -1 -->
- [ ] #53707 <!-- Make ScopedValue public -->
- [ ] #53696 <!-- add invokelatest to on_done callback in bracketed
paste -->
- [ ] #53660 <!-- put Logging back in default sysimage -->
- [ ] #53509 <!-- revert moving "creating packages" from Pkg.jl -->
- [ ] #53452 <!-- RFC: allow Tuple{Union{}}, returning Union{} -->
- [ ] #53402 <!-- Add `jl_getaffinity` and `jl_setaffinity` -->
- [ ] #52694 <!-- Reinstate similar for AbstractQ for backward
compatibility -->
- [ ] #51928 <!-- Styled markdown, with a few tweaks -->
- [ ] #51816 <!-- User-themable stacktraces -->
- [ ] #51811 <!-- Make banner size depend on terminal size -->
- [ ] #51479 <!-- prevent code loading from lookin in the versioned
environment when building Julia -->
@KristofferC KristofferC mentioned this pull request Mar 18, 2024
25 tasks
@JeffBezanson
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I'm not sure this needs to be changed. Looks like the cure might be worse than the disease.

@oscardssmith
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it's really unfortunate that there has to be type weirdness somewhere. that said given the choices we made with literal pow, I think the current behavior unfortunately is just what we're stick with.

@KristofferC KristofferC mentioned this pull request Mar 20, 2024
41 tasks
@KristofferC KristofferC removed backport 1.10 Change should be backported to the 1.10 release backport 1.11 Change should be backported to release-1.11 labels Aug 26, 2024
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Base.literal_pow undesired floating-point conversion for base of ±1?
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