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2 Commits (7aaed5abd512897fc47eef8d0624cc3d4de6cb93)

Author SHA1 Message Date
Anton Blanchard 1b559aee31 Fix count-leading/trailing-zeroes 
The current code simulates correctly, but produces miscompares when synthesized
onto an FPGA. On closer inspection GHDL synthesis complains about inferred
latches and there does seem to be issues.

Convert it to variables that are always initialized to zero at the start of the
process.

Fixes: 24a4a796ce ("execute: Consolidate count-leading/trailing-zeroes implementations")
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
 5 years ago
Paul Mackerras 24a4a796ce execute: Consolidate count-leading/trailing-zeroes implementations 
This adds combinatorial logic that does 32-bit and 64-bit count
leading and trailing zeroes in one unit, and consolidates the
four instructions under a single OP_CNTZ opcode.

This saves 84 slice LUTs on the Arty A7-100.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
 5 years ago