About

These are tasks carried forward from 2024 and some additional work identified in 2024

1. Use Jivan's trick to expose the sign extended nature of SI/HI/QI mode return values.
2. A signed comparison of a sign extended SI subreg against a constant with 0x8000000 clear can be turned into unsigned comparison in DImode
   1. This is a generalization of the min/max case that's currently handled in bitmanip.md.
   2. Investigate if we're already handling this (we may be), and if not explore the best way to fix
3. Investigate Ajit's work (IBM) to exploit cases where masking can be viewed as zero-extension within REE
4. In REE handle cases like (any_extend:DI (ashift:SI )) where the extension can be replaced by a SUBREG and then push the SUBREG into the operands generating word sized operations.  This helps code like this:

void foo(unsigned char *data, unsigned int lo_bit) {
  unsigned int mask = ((1UL << 1) - 1) << lo_bit;
  *data = (*data & ~mask) | ((1 << lo_bit) & mask);
}

One the unnecessary extension is eliminated a simple backend pattern can be used to simplify all that to a simple lb+bset+sb.

Stakeholders/Partners

RISE:

Ventana: Jeff Law

Rivos: Vineet (part time)

External:

Dependencies

Status

Updates

07 Nov 2024 

• New/incomplete items moved into 1H2025