Marius Kamp 170a21e7f0 [InstCombine] Extend Fold of Zero-extended Bit Test (#102100) ...

Previously, (zext (icmp ne (and X, (1 << ShAmt)), 0)) has only been
folded if the bit width of X and the result were equal. Use a trunc or
zext instruction to also support other bit widths.
    
This is a follow-up to commit 533190acdb,
which introduced a regression: (zext (icmp ne (and (lshr X ShAmt) 1) 0))
is not folded any longer to (zext/trunc (and (lshr X ShAmt) 1)) since
the commit introduced the fold of (icmp ne (and (lshr X ShAmt) 1) 0) to
(icmp ne (and X (1 << ShAmt)) 0). The change introduced by this commit
restores this fold.
    
Alive proof: https://alive2.llvm.org/ce/z/MFkNXs
    
Relates to issue #86813 and pull request #101838.

2024-08-21 20:09:02 +08:00

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