[llvm] [CVP] Check whether the default case is reachable (PR #79993)

[Nikita Popov via llvm-commits]

================
@@ -0,0 +1,299 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt < %s -passes=correlated-propagation -S | FileCheck %s
+
+define i32 @test_unreachable_default(i32 noundef %num) {
+; CHECK-LABEL: define i32 @test_unreachable_default(
+; CHECK-SAME: i32 noundef [[NUM:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SUB:%.*]] = add i32 [[NUM]], -120
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[SUB]], 3
+; CHECK-NEXT:    [[COND:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 2
+; CHECK-NEXT:    switch i32 [[COND]], label [[DEFAULT_UNREACHABLE:%.*]] [
+; CHECK-NEXT:      i32 0, label [[SW_BB:%.*]]
+; CHECK-NEXT:      i32 1, label [[SW_BB2:%.*]]
+; CHECK-NEXT:      i32 2, label [[SW_BB4:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       sw.bb:
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @call0()
+; CHECK-NEXT:    br label [[CLEANUP:%.*]]
+; CHECK:       sw.bb2:
+; CHECK-NEXT:    [[CALL3:%.*]] = call i32 @call1()
+; CHECK-NEXT:    br label [[CLEANUP]]
+; CHECK:       sw.bb4:
+; CHECK-NEXT:    [[CALL5:%.*]] = call i32 @call2()
+; CHECK-NEXT:    br label [[CLEANUP]]
+; CHECK:       default.unreachable:
+; CHECK-NEXT:    unreachable
+; CHECK:       sw.default:
+; CHECK-NEXT:    [[CALL6:%.*]] = call i32 @call3()
+; CHECK-NEXT:    br label [[CLEANUP]]
+; CHECK:       cleanup:
+; CHECK-NEXT:    [[RETVAL_0:%.*]] = phi i32 [ [[CALL6]], [[SW_DEFAULT:%.*]] ], [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ]
+; CHECK-NEXT:    ret i32 [[RETVAL_0]]
+;
+entry:
+  %sub = add i32 %num, -120
+  %cmp = icmp ult i32 %sub, 3
+  %cond = select i1 %cmp, i32 %sub, i32 2
+  switch i32 %cond, label %sw.default [
+  i32 0, label %sw.bb
+  i32 1, label %sw.bb2
+  i32 2, label %sw.bb4
+  ]
+
+sw.bb:
+  %call = call i32 @call0()
+  br label %cleanup
+
+sw.bb2:
+  %call3 = call i32 @call1()
+  br label %cleanup
+
+sw.bb4:
+  %call5 = call i32 @call2()
+  br label %cleanup
+
+sw.default:
+  %call6 = call i32 @call3()
+  br label %cleanup
+
+cleanup:
+  %retval.0 = phi i32 [ %call6, %sw.default ], [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ]
+  ret i32 %retval.0
+}
+
+define i32 @test_unreachable_default_shared_edge(i32 noundef %num) {
+; CHECK-LABEL: define i32 @test_unreachable_default_shared_edge(
+; CHECK-SAME: i32 noundef [[NUM:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[SUB:%.*]] = add i32 [[NUM]], -120
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[SUB]], 3
+; CHECK-NEXT:    [[COND:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 2
+; CHECK-NEXT:    switch i32 [[COND]], label [[DEFAULT_UNREACHABLE:%.*]] [
+; CHECK-NEXT:      i32 0, label [[SW_BB:%.*]]
+; CHECK-NEXT:      i32 1, label [[SW_BB2:%.*]]
+; CHECK-NEXT:      i32 2, label [[SW_BB4:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       sw.bb:
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @call0()
+; CHECK-NEXT:    br label [[CLEANUP:%.*]]
+; CHECK:       sw.bb2:
+; CHECK-NEXT:    [[CALL3:%.*]] = call i32 @call1()
+; CHECK-NEXT:    br label [[CLEANUP]]
+; CHECK:       default.unreachable:
+; CHECK-NEXT:    unreachable
+; CHECK:       sw.bb4:
+; CHECK-NEXT:    [[CALL5:%.*]] = call i32 @call2()
+; CHECK-NEXT:    br label [[CLEANUP]]
+; CHECK:       cleanup:
+; CHECK-NEXT:    [[RETVAL_0:%.*]] = phi i32 [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ]
+; CHECK-NEXT:    ret i32 [[RETVAL_0]]
+;
+entry:
+  %sub = add i32 %num, -120
+  %cmp = icmp ult i32 %sub, 3
+  %cond = select i1 %cmp, i32 %sub, i32 2
+  switch i32 %cond, label %sw.bb4 [
+  i32 0, label %sw.bb
+  i32 1, label %sw.bb2
+  i32 2, label %sw.bb4
+  ]
+
+sw.bb:
+  %call = call i32 @call0()
+  br label %cleanup
+
+sw.bb2:
+  %call3 = call i32 @call1()
+  br label %cleanup
+
+sw.bb4:
----------------
nikic wrote:

Please add a phi node to this block.

https://github.com/llvm/llvm-project/pull/79993