fold-popular-case-to-unreachable-default.ll
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; RUN: opt %s -lowerswitch -S | FileCheck %s
define void @foo(i32 %x, i32* %p) {
; Cases 2 and 4 are removed and become the new default case.
; It is now enough to use two icmps to lower the switch.
;
; CHECK-LABEL: @foo
; CHECK: icmp slt i32 %x, 5
; CHECK: icmp eq i32 %x, 1
; CHECK-NOT: icmp
;
entry:
switch i32 %x, label %default [
i32 1, label %bb0
i32 2, label %popular
i32 4, label %popular
i32 5, label %bb1
]
bb0:
store i32 0, i32* %p
br label %exit
bb1:
store i32 1, i32* %p
br label %exit
popular:
store i32 2, i32* %p
br label %exit
exit:
ret void
default:
unreachable
}
define void @unreachable_gap(i64 %x, i32* %p) {
; Cases 6 and INT64_MAX become the new default, but we still exploit the fact
; that 3-4 is unreachable, so four icmps is enough.
; CHECK-LABEL: @unreachable_gap
; CHECK: icmp slt i64 %x, 2
; CHECK: icmp slt i64 %x, 5
; CHECK: icmp eq i64 %x, 5
; CHECK: icmp slt i64 %x, 1
; CHECK-NOT: icmp
entry:
switch i64 %x, label %default [
i64 -9223372036854775808, label %bb0
i64 1, label %bb1
i64 2, label %bb2
i64 5, label %bb3
i64 6, label %bb4
i64 9223372036854775807, label %bb4
]
bb0:
store i32 0, i32* %p
br label %exit
bb1:
store i32 1, i32* %p
br label %exit
bb2:
store i32 2, i32* %p
br label %exit
bb3:
store i32 3, i32* %p
br label %exit
bb4:
store i32 4, i32* %p
br label %exit
exit:
ret void
default:
unreachable
}
define void @nocases(i32 %x, i32* %p) {
; Don't fall over when there are no cases.
;
; CHECK-LABEL: @nocases
; CHECK-LABEL: entry
; CHECK-NEXT: br label %default
;
entry:
switch i32 %x, label %default [
]
default:
unreachable
}
define void @nocasesleft(i32 %x, i32* %p) {
; Cases 2 and 4 are removed and we are left with no cases.
;
; CHECK-LABEL: @nocasesleft
; CHECK-LABEL: entry
; CHECK-NEXT: br label %popular
;
entry:
switch i32 %x, label %default [
i32 2, label %popular
i32 4, label %popular
]
popular:
store i32 2, i32* %p
br label %exit
exit:
ret void
default:
unreachable
}