Rollup merge of #147873 - RalfJung:deduce_param_attrs, r=tmiasko

comments for deduce_param_attrs

Cc `@saethlin` since IIRC you experimented with codegen doing post-mono MIR ops? That seems to be in conflict with this pass.
Cc `@tmiasko`

r? `@scottmcm`

Author: matthiaskrgr