[llvm] [AArch64][SVE] Rework VECTOR_COMPRESS lowering (PR #171162)

[Gaëtan Bossu via llvm-commits]

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@@ -242,14 +238,10 @@ define <4 x double> @test_compress_v4f64_with_sve(<4 x double> %vec, <4 x i1> %m
 ; CHECK-NEXT:    lsr x9, x8, #32
 ; CHECK-NEXT:    eor w8, w8, w9
 ; CHECK-NEXT:    mov x9, sp
-; CHECK-NEXT:    cmlt v3.2d, v3.2d, #0
-; CHECK-NEXT:    cmlt v4.2d, v4.2d, #0
-; CHECK-NEXT:    and x8, x8, #0x3
-; CHECK-NEXT:    lsl x8, x8, #3
-; CHECK-NEXT:    and z3.d, z3.d, #0x1
-; CHECK-NEXT:    and z4.d, z4.d, #0x1
 ; CHECK-NEXT:    cmpne p1.d, p0/z, z3.d, #0
 ; CHECK-NEXT:    cmpne p0.d, p0/z, z4.d, #0
+; CHECK-NEXT:    and x8, x8, #0x3
+; CHECK-NEXT:    lsl x8, x8, #3
 ; CHECK-NEXT:    compact z0.d, p1, z0.d
 ; CHECK-NEXT:    compact z1.d, p0, z1.d
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gbossu wrote:

I'm not sure I understand that lowering. Could you explain what it's doing?

https://github.com/llvm/llvm-project/pull/171162