mirror of
https://github.com/c64scene-ar/llvm-6502.git
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01e223e92e
SimplifyCFG currently does this transformation, but I'm planning to remove that to allow other passes, such as this one, to exploit the unreachable default. This patch takes care to keep track of what case values are unreachable even after the transformation, allowing for more efficient lowering. Differential Revision: http://reviews.llvm.org/D6697 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226934 91177308-0d34-0410-b5e6-96231b3b80d8
111 lines
2.0 KiB
LLVM
111 lines
2.0 KiB
LLVM
; RUN: opt %s -lowerswitch -S | FileCheck %s
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define void @foo(i32 %x, i32* %p) {
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; Cases 2 and 4 are removed and become the new default case.
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; It is now enough to use two icmps to lower the switch.
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;
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; CHECK-LABEL: @foo
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; CHECK: icmp slt i32 %x, 5
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; CHECK: icmp eq i32 %x, 1
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; CHECK-NOT: icmp
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;
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entry:
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switch i32 %x, label %default [
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i32 1, label %bb0
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i32 2, label %popular
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i32 4, label %popular
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i32 5, label %bb1
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]
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bb0:
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store i32 0, i32* %p
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br label %exit
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bb1:
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store i32 1, i32* %p
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br label %exit
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popular:
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store i32 2, i32* %p
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br label %exit
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exit:
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ret void
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default:
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unreachable
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}
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define void @unreachable_gap(i64 %x, i32* %p) {
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; Cases 6 and INT64_MAX become the new default, but we still exploit the fact
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; that 3-4 is unreachable, so four icmps is enough.
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; CHECK-LABEL: @unreachable_gap
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; CHECK: icmp slt i64 %x, 2
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; CHECK: icmp slt i64 %x, 5
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; CHECK: icmp eq i64 %x, 5
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; CHECK: icmp slt i64 %x, 1
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; CHECK-NOT: icmp
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entry:
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switch i64 %x, label %default [
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i64 -9223372036854775808, label %bb0
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i64 1, label %bb1
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i64 2, label %bb2
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i64 5, label %bb3
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i64 6, label %bb4
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i64 9223372036854775807, label %bb4
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]
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bb0:
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store i32 0, i32* %p
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br label %exit
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bb1:
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store i32 1, i32* %p
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br label %exit
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bb2:
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store i32 2, i32* %p
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br label %exit
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bb3:
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store i32 3, i32* %p
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br label %exit
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bb4:
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store i32 4, i32* %p
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br label %exit
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exit:
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ret void
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default:
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unreachable
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}
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define void @nocases(i32 %x, i32* %p) {
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; Don't fall over when there are no cases.
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;
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; CHECK-LABEL: @nocases
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; CHECK-LABEL: entry
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; CHECK-NEXT: br label %default
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;
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entry:
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switch i32 %x, label %default [
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]
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default:
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unreachable
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}
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define void @nocasesleft(i32 %x, i32* %p) {
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; Cases 2 and 4 are removed and we are left with no cases.
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;
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; CHECK-LABEL: @nocasesleft
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; CHECK-LABEL: entry
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; CHECK-NEXT: br label %popular
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;
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entry:
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switch i32 %x, label %default [
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i32 2, label %popular
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i32 4, label %popular
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]
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popular:
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store i32 2, i32* %p
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br label %exit
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exit:
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ret void
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default:
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unreachable
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}
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