Differential D81909 Diff 271457 llvm/test/CodeGen/WebAssembly/switch-unreachable-default.ll

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llvm/test/CodeGen/WebAssembly/switch-unreachable-default.ll

Show All 30 Lines	bb0:
ret i32 0		ret i32 0

bb1:		bb1:
ret i32 1		ret i32 1

unreachable:		unreachable:
unreachable		unreachable
}		}

		; CHECK-LABEL: split:
		; CHECK: .functype split (i32) -> ()
		; CHECK: block
		; CHECK: br_if 0
		; CHECK: block
		; CHECK: block
		; CHECK: br_table {1, 1, 1, 1, 1, 1, 1, 0}
		; CHECK: .LBB1_2
		; CHECK: end_block
		; CHECK: br_table {0, 0, 0}
		; CHECK: .LBB1_3
		; CHECK: end_block
		; CHECK: unreachable
		; CHECK: .LBB1_4
		; CHECK: end_block
		; CHECK: end_function
		define void @split(i8 %c) {
		entry:
		switch i8 %c, label %sw.default [
		i8 114, label %return
		i8 103, label %sw.bb1
		i8 98, label %sw.bb2
		i8 97, label %sw.bb3
		i8 48, label %sw.bb4
		i8 49, label %sw.bb5
		]
		aheejinUnsubmitted Not Done Reply Inline Actions Unrelated question: why does this switch get split? Because it’s too big? If so, big br_tables are also bad for wasm too? aheejin: Unrelated question: why does this switch get split? Because it’s too big? If so, big br_tables…
		tlivelyAuthorUnsubmitted Done Reply Inline Actions Right, it's because the case indices are clustered into different groups that are far away from each other. The target-independent codegen has a lot of logic for figuring out how to best split up and group the switch cases to create only reasonably-dense jump tables. This is good for uncompressed WebAssembly as well, although a sparse br_table would still compress well. I don't know if any engines do clever lowerings of br_tables, but we want to make naively lowering them into native jump tables a reasonable option as well, so it is good to have this logic in the tools. tlively: Right, it's because the case indices are clustered into different groups that are far away from…

		sw.bb1:
		unreachable

		sw.bb2:
		unreachable

		sw.bb3:
		unreachable

		sw.bb4:
		unreachable

		sw.bb5:
		unreachable

		sw.default:
		unreachable

		return:
		ret void
		}