The existing non-builtin implementation is returning wrong results.
For example, given the value 63 as a uint8_t it returns 38 (should be 6).
The new implementation follows the naive algorithm presented in figure 5-1
in Hacker's Delight section 5-1.
Note that the algorithm in the book is designed for 32 bit numbers, so we
extended it to support 64 bit as well.
Bug: chromium:1056170
Change-Id: I8fed9c449f80b01b8cc93d339529c0e1e0863fc0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2199345
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67801}
{WhichPowerOf2} is basically the same as {CountTrailingZeros}, with a
restriction to powers of two. Since it does not use or depend on any v8
internals, it can be moved to src/base/bits.h.
This CL also changes the implementation to use the CTZ builtin if
available, and falls back to popcnt otherwise.
Drive-by: Make it constexpr, and rename to {WhichPowerOfTwo}.
R=sigurds@chromium.org
Bug: v8:9810, v8:8912
Change-Id: I8368d098f9ab1247f3b9f036f1385a38de10cc6a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1903966
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64851}
This patch normalizes the casing of hexadecimal digits in escape
sequences of the form `\xNN` and integer literals of the form
`0xNNNN`.
Previously, the V8 code base used an inconsistent mixture of uppercase
and lowercase.
Google’s C++ style guide uses uppercase in its examples:
https://google.github.io/styleguide/cppguide.html#Non-ASCII_Characters
Moreover, uppercase letters more clearly stand out from the lowercase
`x` (or `u`) characters at the start, as well as lowercase letters
elsewhere in strings.
BUG=v8:7109
TBR=marja@chromium.org,titzer@chromium.org,mtrofin@chromium.org,mstarzinger@chromium.org,rossberg@chromium.org,yangguo@chromium.org,mlippautz@chromium.org
NOPRESUBMIT=true
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I790e21c25d96ad5d95c8229724eb45d2aa9e22d6
Reviewed-on: https://chromium-review.googlesource.com/804294
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49810}
V8_INT64_C will be cleaned up in a follow-up CL.
R=tebbi@chromium.org,mlippautz@chromium.org
Bug: v8:7109
Change-Id: I6af97e7266039eb443896b404b77b8e2b5de5adb
Reviewed-on: https://chromium-review.googlesource.com/803294
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49790}
This is a reland of 7d231e576a, fixed to
avoid instantiating CountLeadingZeros for bits==0.
Original change's description:
> [bits] Consolidate Count{Leading,Trailing}Zeros
>
> Instead of having one method for 32 bit integers and one for 64 bit,
> plus a templatized version to choose from those two, just implement one
> version which handles unsigned integers of any size. Also, make them
> constexpr.
> The Count{Leading,Trailing}Zeros{32,64} methods are kept for now in
> order to keep the amount of code changes small. Also, sometimes it
> improves readability by stating exactly the size of the argument,
> especially for leading zeros (where zero-extending would add more
> leading zeros).
>
> CountLeadingZeros now uses a binary search inspired implementation
> as proposed in Hacker's Delight. It's more than 20% faster on x64 if
> the builtins are disabled.
> CountTrailingZeros falls back to CountPopulation instead of counting in
> a naive loop. This is ~50% faster.
>
> R=mstarzinger@chromium.org
>
> Change-Id: I1d8bf1d7295b930724163248150444bd17fbb34e
> Reviewed-on: https://chromium-review.googlesource.com/741231
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49106}
Change-Id: Icdff2510ec66d1c96a1912cef29d77d8550994ee
Reviewed-on: https://chromium-review.googlesource.com/753903
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49138}
This reverts commit 7d231e576a.
Reason for revert: Breaks revert for win-clang:
https://build.chromium.org/p/tryserver.chromium.win/builders/win_clang/builds/342755
Original change's description:
> [bits] Consolidate Count{Leading,Trailing}Zeros
>
> Instead of having one method for 32 bit integers and one for 64 bit,
> plus a templatized version to choose from those two, just implement one
> version which handles unsigned integers of any size. Also, make them
> constexpr.
> The Count{Leading,Trailing}Zeros{32,64} methods are kept for now in
> order to keep the amount of code changes small. Also, sometimes it
> improves readability by stating exactly the size of the argument,
> especially for leading zeros (where zero-extending would add more
> leading zeros).
>
> CountLeadingZeros now uses a binary search inspired implementation
> as proposed in Hacker's Delight. It's more than 20% faster on x64 if
> the builtins are disabled.
> CountTrailingZeros falls back to CountPopulation instead of counting in
> a naive loop. This is ~50% faster.
>
> R=mstarzinger@chromium.org
>
> Change-Id: I1d8bf1d7295b930724163248150444bd17fbb34e
> Reviewed-on: https://chromium-review.googlesource.com/741231
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49106}
TBR=mstarzinger@chromium.org,clemensh@chromium.org
Change-Id: Iceeb35bf9c7539a1013c9bdbc47118008611bef2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/753463
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49123}
Instead of having one method for 32 bit integers and one for 64 bit,
plus a templatized version to choose from those two, just implement one
version which handles unsigned integers of any size. Also, make them
constexpr.
The Count{Leading,Trailing}Zeros{32,64} methods are kept for now in
order to keep the amount of code changes small. Also, sometimes it
improves readability by stating exactly the size of the argument,
especially for leading zeros (where zero-extending would add more
leading zeros).
CountLeadingZeros now uses a binary search inspired implementation
as proposed in Hacker's Delight. It's more than 20% faster on x64 if
the builtins are disabled.
CountTrailingZeros falls back to CountPopulation instead of counting in
a naive loop. This is ~50% faster.
R=mstarzinger@chromium.org
Change-Id: I1d8bf1d7295b930724163248150444bd17fbb34e
Reviewed-on: https://chromium-review.googlesource.com/741231
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49106}
This makes the function constexpr and implements it for arbitrary
unsigned integer types (up to 64 bits, but this can be extended if
needed).
R=mstarzinger@chromium.org
Bug: v8:6600, v8:6921
Change-Id: I86d427238fadd55abb5a27f31ed648d4b02fc358
Reviewed-on: https://chromium-review.googlesource.com/718457
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48696}
There is just one version now, called IsPowerOfTwo. It accepts any
integral type.
There is one slight semantical change: Called with kMinInt, it
previously returned true, because the argument was implicitly casted to
an unsigned. It's now (correctly) returning false, so I had to add
special handlings of kMinInt in machine-operator-reducer before calling
IsPowerOfTwo on that value.
R=mlippautz@chromium.org,mstarzinger@chromium.org,jgruber@chromium.org,ishell@chromium.org,yangguo@chromium.org
Change-Id: Idc112a89034cdc8c03365b778b33b1c29fefb38d
Reviewed-on: https://chromium-review.googlesource.com/568140
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46627}
This makes it possible for automated tests to distinguish between CHECK
failures and DCHECK failures, the latter of which will continue to run
in release builds after the assertion failure point.
Change-Id: Ie26978c0342d401a8c85f3261749739195087579
Reviewed-on: https://chromium-review.googlesource.com/565515
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46596}
With fix for architectures where x<<32 != x.
Original change's description:
> [base] Introduce RoundUpToPowerOfTwo64
>
> And fix RoundUpToPowerOfTwo32 to return 1 for the input 0.
> 0 is no power of two.
> Beside being the correct value, this also avoids a special case in the
> (new) fast path using the number of leading zeros.
>
> R=jochen@chromium.org, ahaas@chromium.org
>
> Change-Id: I87173495e13b334954bcebbb55724fb666dfa809
> Reviewed-on: https://chromium-review.googlesource.com/488143
> Reviewed-by: Jochen Eisinger <jochen@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#44925}
TBR=ahaas@chromium.org,jochen@chromium.org,clemensh@chromium.org,v8-reviews@googlegroups.com
Change-Id: I7b4719d84a419bb7b38e3b5c9d6d183275087ace
Reviewed-on: https://chromium-review.googlesource.com/488981
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44951}
This reverts commit 9ceaf21272.
Reason for revert: Fails on arm: http://build.chromium.org/p/client.v8.ports/builders/V8%20Arm%20-%20debug/builds/2950/steps/Check/logs/Bits.RoundUpToPowerOf..
Original change's description:
> [base] Introduce RoundUpToPowerOfTwo64
>
> And fix RoundUpToPowerOfTwo32 to return 1 for the input 0.
> 0 is no power of two.
> Beside being the correct value, this also avoids a special case in the
> (new) fast path using the number of leading zeros.
>
> R=jochen@chromium.org, ahaas@chromium.org
>
> Change-Id: I87173495e13b334954bcebbb55724fb666dfa809
> Reviewed-on: https://chromium-review.googlesource.com/488143
> Reviewed-by: Jochen Eisinger <jochen@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#44925}
TBR=ahaas@chromium.org,jochen@chromium.org,clemensh@chromium.org,v8-reviews@googlegroups.com,wasm-v8@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
Change-Id: Ib353ee0a944316da6f919bac3bb88d4f95d98ea0
Reviewed-on: https://chromium-review.googlesource.com/488365
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44935}
And fix RoundUpToPowerOfTwo32 to return 1 for the input 0.
0 is no power of two.
Beside being the correct value, this also avoids a special case in the
(new) fast path using the number of leading zeros.
R=jochen@chromium.org, ahaas@chromium.org
Change-Id: I87173495e13b334954bcebbb55724fb666dfa809
Reviewed-on: https://chromium-review.googlesource.com/488143
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44925}
Up until now we used int32_t for NodeId, but that was not ideal because
negative values are invalid for NodeId and we use it as an array index
for example in the NodeMarker class, where C++ compilers on x64 have to
generate code that does proper sign extension for the indices, which is
completely unnecessary.
R=svenpanne@chromium.org
Review URL: https://codereview.chromium.org/1178403004
Cr-Commit-Position: refs/heads/master@{#28997}
