Arnold Schwaighofer 65457b679a Costmodel: Add support for horizontal vector reductions ... Upcoming SLP vectorization improvements will want to be able to estimate costs of horizontal reductions. Add infrastructure to support this. We model reductions as a series of (shufflevector,add) tuples ultimately followed by an extractelement. For example, for an add-reduction of <4 x float> we could generate the following sequence: (v0, v1, v2, v3) \ \ / / \ \ / + + (v0+v2, v1+v3, undef, undef) \ / ((v0+v2) + (v1+v3), undef, undef) %rdx.shuf = shufflevector <4 x float> %rdx, <4 x float> undef, <4 x i32> <i32 2, i32 3, i32 undef, i32 undef> %bin.rdx = fadd <4 x float> %rdx, %rdx.shuf %rdx.shuf7 = shufflevector <4 x float> %bin.rdx, <4 x float> undef, <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef> %bin.rdx8 = fadd <4 x float> %bin.rdx, %rdx.shuf7 %r = extractelement <4 x float> %bin.rdx8, i32 0 This commit adds a cost model interface "getReductionCost(Opcode, Ty, Pairwise)" that will allow clients to ask for the cost of such a reduction (as backends might generate more efficient code than the cost of the individual instructions summed up). This interface is excercised by the CostModel analysis pass which looks for reduction patterns like the one above - starting at extractelements - and if it sees a matching sequence will call the cost model interface. We will also support a second form of pairwise reduction that is well supported on common architectures (haddps, vpadd, faddp). (v0, v1, v2, v3) \ / \ / (v0+v1, v2+v3, undef, undef) \ / ((v0+v1)+(v2+v3), undef, undef, undef) %rdx.shuf.0.0 = shufflevector <4 x float> %rdx, <4 x float> undef, <4 x i32> <i32 0, i32 2 , i32 undef, i32 undef> %rdx.shuf.0.1 = shufflevector <4 x float> %rdx, <4 x float> undef, <4 x i32> <i32 1, i32 3, i32 undef, i32 undef> %bin.rdx.0 = fadd <4 x float> %rdx.shuf.0.0, %rdx.shuf.0.1 %rdx.shuf.1.0 = shufflevector <4 x float> %bin.rdx.0, <4 x float> undef, <4 x i32> <i32 0, i32 undef, i32 undef, i32 undef> %rdx.shuf.1.1 = shufflevector <4 x float> %bin.rdx.0, <4 x float> undef, <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef> %bin.rdx.1 = fadd <4 x float> %rdx.shuf.1.0, %rdx.shuf.1.1 %r = extractelement <4 x float> %bin.rdx.1, i32 0 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190876 91177308-0d34-0410-b5e6-96231b3b80d8		2013-09-17 18:06:50 +00:00
..
llvm	Costmodel: Add support for horizontal vector reductions	2013-09-17 18:06:50 +00:00
llvm-c	Revert 189297, the original commit message is following.	2013-08-27 17:15:54 +00:00