| Issue |
177369
|
| Summary |
[X86] SimplifyDemandedBitsForTargetNode - add X86ISD::BZHI handling
|
| Labels |
good first issue,
backend:X86
|
| Assignees |
|
| Reporter |
RKSimon
|
- [ ] Only the bottom 8 bits of the mask (second operand) are required
- [ ] Based off the known bits of the mask, we can tweak the src DemandedBits - as well as the incoming DemandedBits mask, if the 8 bit mask is known to be less than bitwidth (`getMaxValue.ult(BitWidth)`) then bits above getMaxValue are not demanded.
Supporting tests can be added to combine-bzhi.ll
See also #177347 and #177364 for refs
https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=bzhi&ig_expand=634,633,5,634
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