VEC_SLO has an error in description about the location of the shift amount #104

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opened 4 years ago by cjashfor · 1 comments
cjashfor commented 4 years ago (Migrated from github.com)

The description has this text:
Result value:
The result is the contents of ARG1, shifted left by the number of bytes specified by the
most-significant nibble of the least-significant byte of ARG2. The bits that are shifted out
are replaced by zeros.

And there's a note that says: "That is, by little-endian bits 7–4 or big-endian bits 121–124."

There's a contradiction, though, because bits 121-124 are not the upper nibble, which would be 120-123. I verified through debugging my code which uses this instruction that 121-124 are the correct bit numbers.

The sister function - VEC_SRO - description does not contain this error.

The description has this text: Result value: The result is the contents of ARG1, shifted left by the number of bytes specified by the most-significant nibble of the least-significant byte of ARG2. The bits that are shifted out are replaced by zeros. And there's a note that says: "That is, by little-endian bits 7–4 or big-endian bits 121–124." There's a contradiction, though, because bits 121-124 are not the upper nibble, which would be 120-123. I verified through debugging my code which uses this instruction that 121-124 are the correct bit numbers. The sister function - VEC_SRO - description does not contain this error.
wschmidt-ibm commented 4 years ago (Migrated from github.com)

This is already fixed in the PVIPR document that will replace this appendix. That says:

"Vector r receives the contents of a, shifted left by the number of bytes specified by
bits 1:4 of the least-significant byte of b."

Since this Appendix will be deleted in the next version, I'm closing this as fix-available.

This is already fixed in the PVIPR document that will replace this appendix. That says: "Vector r receives the contents of a, shifted left by the number of bytes specified by bits 1:4 of the least-significant byte of b." Since this Appendix will be deleted in the next version, I'm closing this as fix-available.
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Reference: systemsoftware/ELFv2-ABI#104
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