[RISCV] Add some tests showing vsetvli cleanup opportunities

[frasercrmck]

This came up in testing. I'm not planning on fixing this immediately, so I thought I'd put them up in case they inspire anyone. I can take a look in the next few weeks.

[frasercrmck]

In D99717#2663463, @frasercrmck wrote:

This came up in testing. I'm not planning on fixing this immediately, so I thought I'd put them up in case they inspire anyone. I can take a look in the next few weeks.

Okay, that said, it doesn't look like a big job so I'm sure I can find the time.

[frasercrmck]

• add another case where a redundant vsetvli hasn't got a dead output

[craig.topper]

LGTM

llvm/test/CodeGen/RISCV/rvv/rv32-vsetvli-intrinsics.ll

 define void @test_vsetvlimax_e64m8() nounwind {
 ; CHECK-LABEL: test_vsetvlimax_e64m8:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    vsetvli a0, zero, e64,m8,ta,mu
 ; CHECK-NEXT:    ret
   call i32 @llvm.riscv.vsetvlimax.i32(i32 3, i32 3)
   ret void
 }
+
+declare <vscale x 4 x i32> @llvm.riscv.vle.nxv4i32.i32(<vscale x 4 x i32>*, i32)
+
+; Check that we remove the redundant vsetvli when followed by another operation
+; FIXME: We don't
+define <vscale x 4 x i32> @redundant_vsetvli(i32 %avl, <vscale x 4 x i32>* %ptr) nounwind {
+; CHECK-LABEL: redundant_vsetvli:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli a0, a0, e32,m2,ta,mu
+; CHECK-NEXT:    vsetvli a0, a0, e32,m2,ta,mu
+; CHECK-NEXT:    vle32.v v8, (a1)
+; CHECK-NEXT:    ret
+  %vl = call i32 @llvm.riscv.vsetvli.i32(i32 %avl, i32 2, i32 1)
+  %x = call <vscale x 4 x i32> @llvm.riscv.vle.nxv4i32.i32(<vscale x 4 x i32>* %ptr, i32 %vl)
+  ret <vscale x 4 x i32> %x
+}

llvm/test/CodeGen/RISCV/rvv/rv64-vsetvli-intrinsics.ll

 define void @test_vsetvlimax_e64m4() nounwind {
 ; CHECK-LABEL: test_vsetvlimax_e64m4:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    vsetvli a0, zero, e64,m4,ta,mu
 ; CHECK-NEXT:    ret
   call i64 @llvm.riscv.vsetvlimax.i64(i64 3, i64 2)
   ret void
 }
+
+declare <vscale x 4 x i32> @llvm.riscv.vle.nxv4i32.i64(<vscale x 4 x i32>*, i64)
+
+; Check that we remove the redundant vsetvli when followed by another operation
+; FIXME: We don't
+define <vscale x 4 x i32> @redundant_vsetvli(i64 %avl, <vscale x 4 x i32>* %ptr) nounwind {
+; CHECK-LABEL: redundant_vsetvli:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli a0, a0, e32,m2,ta,mu
+; CHECK-NEXT:    vsetvli a0, a0, e32,m2,ta,mu
+; CHECK-NEXT:    vle32.v v8, (a1)
+; CHECK-NEXT:    ret
+  %vl = call i64 @llvm.riscv.vsetvli.i64(i64 %avl, i64 2, i64 1)
+  %x = call <vscale x 4 x i32> @llvm.riscv.vle.nxv4i32.i64(<vscale x 4 x i32>* %ptr, i64 %vl)
+  ret <vscale x 4 x i32> %x
+}