This patch adds improvements for sext/zext of a vector extract in Global
ISel.
For example, this piece of code:
define i64 @si64(<4 x i32> %0, i32 %1) {
%3 = extractelement <4 x i32> %0, i64 1
%s = sext i32 %3 to i64
ret i64 %s
}
Used to have this lowering:
si64:
mov s0, v0.s[1]
fmov w8, s0
sxtw x0, w8
ret
Whereas this patch makes it lower to this:
si64:
smov x0, v0.h[0]
ret
Differential Revision: https://reviews.llvm.org/D108137
7023cefe61