Skip to content
Commit 265995ef authored by Simon Pilgrim's avatar Simon Pilgrim
Browse files

[X86][SSSE3] Lower vector CTLZ with PSHUFB lookups 

This patch uses PSHUFB to lower vector CTLZ and avoid (slower) scalarizations.

The leading zero count of each 4-bit nibble of the vector is determined by using a PSHUFB lookup. Pairs of results are then repeatedly combined up to the original element width.

Differential Revision: http://reviews.llvm.org/D20016

llvm-svn: 269646
parent 68570b20
Expand all Show whitespace changes
Inline Side-by-side
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Please to comment