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Author	SHA1	Message	Date
Roman Lebedev	cc0216bedb	[NFC][InstCombine] '(X & (- Y)) - X' -> '- (X & (Y - 1))' fold (PR44448) Name: (X & (- Y)) - X -> - (X & (Y - 1)) (PR44448) %negy = sub i8 0, %y %unbiasedx = and i8 %negy, %x %r = sub i8 %unbiasedx, %x => %ymask = add i8 %y, -1 %xmasked = and i8 %ymask, %x %r = sub i8 0, %xmasked https://rise4fun.com/Alive/OIpla This decreases use count of %x, may allow us to later hoist said negation even further, and results in marginally nicer X86 codegen. See https://bugs.llvm.org/show_bug.cgi?id=44448 https://reviews.llvm.org/D71499	2020-01-03 20:27:29 +03:00
Roman Lebedev	b87a351182	[NFC][InstCombine] '(X & (- Y)) - X' pattern tests (PR44448) As discussed in https://bugs.llvm.org/show_bug.cgi?id=44448, we can hoist negation out of the pattern.	2020-01-03 20:27:17 +03:00

Author

SHA1

Message

Date

Roman Lebedev

cc0216bedb

[NFC][InstCombine] '(X & (- Y)) - X' -> '- (X & (Y - 1))' fold (PR44448)

Name: (X & (- Y)) - X  ->  - (X & (Y - 1))  (PR44448)
  %negy = sub i8 0, %y
  %unbiasedx = and i8 %negy, %x
  %r = sub i8 %unbiasedx, %x
=>
  %ymask = add i8 %y, -1
  %xmasked = and i8 %ymask, %x
  %r = sub i8 0, %xmasked

https://rise4fun.com/Alive/OIpla

This decreases use count of %x, may allow us to
later hoist said negation even further,
and results in marginally nicer X86 codegen.

See
  https://bugs.llvm.org/show_bug.cgi?id=44448
  https://reviews.llvm.org/D71499

2020-01-03 20:27:29 +03:00

Roman Lebedev

b87a351182

[NFC][InstCombine] '(X & (- Y)) - X' pattern tests (PR44448)

As discussed in https://bugs.llvm.org/show_bug.cgi?id=44448,
we can hoist negation out of the pattern.

2020-01-03 20:27:17 +03:00

2 Commits