Matt Pharr bba84f247c Improved optimization of vector select instructions. ...

Various LLVM optimization passes are turning code like:

%cmp = icmp lt <8 x i32> %foo, %bar
%cmp32 = sext <8 x i1> %cmp to <8 x i32>
. . .
%cmp1 = trunc <8 x i32> %cmp32 to <8 x i1>
%result = select <8 x i1> %cmp1, . . .

Into:

%cmp = icmp lt <8 x i32> %foo, %bar
%cmp32 = zext <8 x i1> %cmp to <8 x i32>   # note: zext
. . .
%cmp1 = icmp ne <8 x i32> %cmp32, zeroinitializer
%result = select <8 x i1> %cmp1, …

Which in turn isn't matched well by the LLVM code generators, which
in turn leads to fairly inefficient code.  (i.e. it doesn't just emit
a vector compare and blend instruction.)

Also, renamed VSelMovmskOptPass to InstructionSimplifyPass to better
describe its functionality.

2013-07-25 09:46:01 -07:00

183 KiB

Raw Blame History

View Raw