[AArch64] Add a tablegen pattern for UZP2.

[labrinea]

Summary

Converts concat_vectors((trunc (lshr)), (trunc (lshr))) to UZP2 when the shift amount is half the width of the vector element.

[SjoerdMeijer]

llvm/test/CodeGen/AArch64/uzp2.ll

5 ↗

(On Diff #395391)

Just a nit about the tests: rather than adding a new file, would it make sense to keep all uzp2 tests together in existing file arm64-uzp.ll?

[labrinea]

llvm/test/CodeGen/AArch64/uzp2.ll

5 ↗

(On Diff #395391)

Can do, but that file doesn't seem to test combination patterns. Maybe I could rename this file into something that indicates combine?

[SjoerdMeijer]

llvm/test/CodeGen/AArch64/uzp2.ll

5 ↗

(On Diff #395391)

Yeah, that would also work, e.g. arm64-uzp-combine.ll or something along those lines would group this together.

LGTM

[lebedev.ri]

Hello.
Is this regression expected: https://godbolt.org/z/c7Kbor6Th ?
This affected halide CI https://buildbot.halide-lang.org/master/#/builders/173/builds/500/steps/12/logs/correctness_simd_op_check

[lebedev.ri]

In D116021#3212514, @lebedev.ri wrote:

Hello.
Is this regression expected: https://godbolt.org/z/c7Kbor6Th ?
This affected halide CI https://buildbot.halide-lang.org/master/#/builders/173/builds/500/steps/12/logs/correctness_simd_op_check

No, bad example, there it isn't obvious that there is a regression.
How about this one: https://godbolt.org/z/EeqjGW58x <- clear increase in instruction count.

llvm/lib/Target/AArch64/AArch64InstrInfo.td

def : Pat<(v16i8 (concat_vectors (v8i8 (trunc (v8i16 V128:$Vn))),
           (UZP1v16i8 V128:$Vn, V128:$Vm)>;
 def : Pat<(v8i16 (concat_vectors (v4i16 (trunc (v4i32 V128:$Vn))),
                                  (v4i16 (trunc (v4i32 V128:$Vm))))),
           (UZP1v8i16 V128:$Vn, V128:$Vm)>;
 def : Pat<(v4i32 (concat_vectors (v2i32 (trunc (v2i64 V128:$Vn))),
                                  (v2i32 (trunc (v2i64 V128:$Vm))))),
           (UZP1v4i32 V128:$Vn, V128:$Vm)>;
 
+def : Pat<(v16i8 (concat_vectors
+                 (v8i8 (trunc (AArch64vlshr (v8i16 V128:$Vn), (i32 8)))),
+                 (v8i8 (trunc (AArch64vlshr (v8i16 V128:$Vm), (i32 8)))))),
+          (UZP2v16i8 V128:$Vn, V128:$Vm)>;
+def : Pat<(v8i16 (concat_vectors
+                 (v4i16 (trunc (AArch64vlshr (v4i32 V128:$Vn), (i32 16)))),
+                 (v4i16 (trunc (AArch64vlshr (v4i32 V128:$Vm), (i32 16)))))),
+          (UZP2v8i16 V128:$Vn, V128:$Vm)>;
+def : Pat<(v4i32 (concat_vectors
+                 (v2i32 (trunc (AArch64vlshr (v2i64 V128:$Vn), (i32 32)))),
+                 (v2i32 (trunc (AArch64vlshr (v2i64 V128:$Vm), (i32 32)))))),
+          (UZP2v4i32 V128:$Vn, V128:$Vm)>;
+
 //----------------------------------------------------------------------------
 // AdvSIMD TBL/TBX instructions
 //----------------------------------------------------------------------------
 
 defm TBL : SIMDTableLookup<    0, "tbl">;
 defm TBX : SIMDTableLookupTied<1, "tbx">;
 
 def : Pat<(v8i8 (int_aarch64_neon_tbl1 (v16i8 VecListOne128:$Rn), (v8i8 V64:$Ri))),

llvm/test/CodeGen/AArch64/arm64-uzp2-combine.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple aarch64-none-linux-gnu | FileCheck %s
+
+; Test the (concat_vectors (trunc (lshr)), (trunc (lshr))) pattern.
+
+define <16 x i8> @test_combine_v8i16_to_v16i8(<8 x i16> %x, <8 x i16> %y) {
+; CHECK-LABEL: test_combine_v8i16_to_v16i8:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    uzp2 v0.16b, v0.16b, v1.16b
+; CHECK-NEXT:    ret
+entry:
+  %lshr1 = lshr <8 x i16> %x, <i16 8, i16 8, i16 8, i16 8, i16 8, i16 8, i16 8, i16 8>
+  %trunc1 = trunc <8 x i16> %lshr1 to <8 x i8>
+  %lshr2 = lshr <8 x i16> %y, <i16 8, i16 8, i16 8, i16 8, i16 8, i16 8, i16 8, i16 8>
+  %trunc2 = trunc <8 x i16> %lshr2 to <8 x i8>
+  %shuffle = shufflevector <8 x i8> %trunc1, <8 x i8> %trunc2, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  ret <16 x i8> %shuffle
+}
+
+define <8 x i16> @test_combine_v4i32_to_v8i16(<4 x i32> %x, <4 x i32> %y) {
+; CHECK-LABEL: test_combine_v4i32_to_v8i16:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    uzp2 v0.8h, v0.8h, v1.8h
+; CHECK-NEXT:    ret
+entry:
+  %lshr1 = lshr <4 x i32> %x, <i32 16, i32 16, i32 16, i32 16>
+  %trunc1 = trunc <4 x i32> %lshr1 to <4 x i16>
+  %lshr2 = lshr <4 x i32> %y, <i32 16, i32 16, i32 16, i32 16>
+  %trunc2 = trunc <4 x i32> %lshr2 to <4 x i16>
+  %shuffle = shufflevector <4 x i16> %trunc1, <4 x i16> %trunc2, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  ret <8 x i16> %shuffle
+}
+
+define <4 x i32> @test_combine_v2i64_to_v4i32(<2 x i64> %x, <2 x i64> %y) {
+; CHECK-LABEL: test_combine_v2i64_to_v4i32:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    uzp2 v0.4s, v0.4s, v1.4s
+; CHECK-NEXT:    ret
+entry:
+  %lshr1 = lshr <2 x i64> %x, <i64 32, i64 32>
+  %trunc1 = trunc <2 x i64> %lshr1 to <2 x i32>
+  %lshr2 = lshr <2 x i64> %y, <i64 32, i64 32>
+  %trunc2 = trunc <2 x i64> %lshr2 to <2 x i32>
+  %shuffle = shufflevector <2 x i32> %trunc1, <2 x i32> %trunc2, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  ret <4 x i32> %shuffle
+}
+