[PATCH] D75801: [InstCombine] Remove known bits constant folding (WIP)

Sat Mar 14 11:15:59 PDT 2020

lebedev.ri added a comment.

In D75801#1922970 <https://reviews.llvm.org/D75801#1922970>, @nikic wrote:

> @lebedev.ri Finally got around to implementing some compile-time testing infrastructure today, here's some numbers (in terms of instructions retired) for this change: F11561365: Screenshot from 2020-03-14 18-03-53.png <https://reviews.llvm.org/F11561365> Basically this is a 1-2% end-to-end improvement for `-O3` compile-times.

Thank you, so this does indeed have some measurable effect.
Sounds justified then.

In D75801#1912306 <https://reviews.llvm.org/D75801#1912306>, @lebedev.ri wrote:

> Do we do this fold somewhere else in the pipeline?

?
Do we believe CVP/SCCP/??? will cover all the possible cases?

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https://reviews.llvm.org/D75801