https://bugs.llvm.org/show_bug.cgi?id=46894
Bug ID: 46894
Summary: Fold smax(shuffle(x,undef,m),shuffle(y,undef,m)) ->
shuffle(smax(x,y),undef,m)
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected]
For standard binary operators, instcombine optimizes:
define <2 x i64> @swap_mul(<2 x i64> %a0, <2 x i64> %a1) {
%a = shufflevector <2 x i64> %a0, <2 x i64> %a1, <2 x i32> <i32 1, i32 0>
%b = shufflevector <2 x i64> %a0, <2 x i64> %a1, <2 x i32> <i32 1, i32 0>
%r = mul <2 x i64> %a, %b
ret <2 x i64> %r
}
-->
define <2 x i64> @swap_mul(<2 x i64> %a0, <2 x i64> %a1) {
%1 = mul <2 x i64> %a0, %a0
%r = shufflevector <2 x i64> %1, <2 x i64> undef, <2 x i32> <i32 1, i32 0>
ret <2 x i64> %r
}
But we there's no way to do this for binop style intrinsics
(smax/smin/umax/umin):
define <2 x i64> @swap_smax(<2 x i64> %a0, <2 x i64> %a1) {
%a = shufflevector <2 x i64> %a0, <2 x i64> %a1, <2 x i32> <i32 1, i32 0>
%b = shufflevector <2 x i64> %a0, <2 x i64> %a1, <2 x i32> <i32 1, i32 0>
%r = call <2 x i64> @llvm.smax.v2i64(<2 x i64> %a, <2 x i64> %b)
ret <2 x i64> %r
}
declare <2 x i64> @llvm.smax.v2i64(<2 x i64>, <2 x i64>)
As a stretch goal we could do this for triop intrinsics, such as fshl/fshr, as
well:
define <2 x i64> @swap_fshl(<2 x i64> %a0, <2 x i64> %a1, <2 x i64> %a2) {
%a = shufflevector <2 x i64> %a0, <2 x i64> %a0, <2 x i32> <i32 1, i32 0>
%b = shufflevector <2 x i64> %a1, <2 x i64> %a1, <2 x i32> <i32 1, i32 0>
%c = shufflevector <2 x i64> %a2, <2 x i64> %a2, <2 x i32> <i32 1, i32 0>
%r = call <2 x i64> @llvm.fshl.v2i64(<2 x i64> %a, <2 x i64> %b, <2 x i64>
%c)
ret <2 x i64> %r
}
declare <2 x i64> @llvm.fshl.v2i64(<2 x i64>, <2 x i64>, <2 x i64>)
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