[SimplifyCFG] Precommit test (NFC)

Author: antoniofrighetto

llvm/test/Transforms/SimplifyCFG/X86/switch-of-powers-of-two.ll

@@ -0,0 +1,50 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes='simplifycfg<switch-to-lookup>' -simplifycfg-require-and-preserve-domtree=1 -S < %s | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @switch_of_powers_two(i32 %arg) {
+; CHECK-LABEL: @switch_of_powers_two(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    switch i32 [[ARG:%.*]], label [[DEFAULT_CASE:%.*]] [
+; CHECK-NEXT:      i32 1, label [[RETURN:%.*]]
+; CHECK-NEXT:      i32 8, label [[BB2:%.*]]
+; CHECK-NEXT:      i32 16, label [[BB3:%.*]]
+; CHECK-NEXT:      i32 32, label [[BB4:%.*]]
+; CHECK-NEXT:      i32 64, label [[BB5:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       default_case:
+; CHECK-NEXT:    unreachable
+; CHECK:       bb2:
+; CHECK-NEXT:    br label [[RETURN]]
+; CHECK:       bb3:
+; CHECK-NEXT:    br label [[RETURN]]
+; CHECK:       bb4:
+; CHECK-NEXT:    br label [[RETURN]]
+; CHECK:       bb5:
+; CHECK-NEXT:    br label [[RETURN]]
+; CHECK:       return:
+; CHECK-NEXT:    [[SWITCH_LOAD:%.*]] = phi i32 [ 2, [[BB2]] ], [ 1, [[BB3]] ], [ 0, [[BB4]] ], [ 42, [[BB5]] ], [ 3, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    ret i32 [[SWITCH_LOAD]]
+;
+entry:
+  switch i32 %arg, label %default_case [
+  i32 1,  label %bb1
+  i32 8,  label %bb2
+  i32 16, label %bb3
+  i32 32, label %bb4
+  i32 64, label %bb5
+  ]
+
+
+default_case: unreachable
+bb1: br label %return
+bb2: br label %return
+bb3: br label %return
+bb4: br label %return
+bb5: br label %return
+
+return:
+  %phi = phi i32 [ 3, %bb1 ], [ 2, %bb2 ], [ 1, %bb3 ], [ 0, %bb4 ], [ 42, %bb5 ]
+  ret i32 %phi
+}