[Mlir-commits] [mlir] [MLIR][CF] Avoid collapsing blocks which participate in cycles (PR #160783)

[Matthias Springer]

================
@@ -490,3 +490,139 @@ func.func @branchCondProp(%arg0: i1) {
 ^exit:
   return
 }
+
+// -----
+
+/// Test that control-flow cycles are not simplified infinitely.
+
+// CHECK-LABEL:   @cycle_2_blocks
+// CHECK:           cf.br ^bb1
+// CHECK:         ^bb1:
+// CHECK:           cf.br ^bb1
+func.func @cycle_2_blocks() {
+  cf.br ^bb1
+  ^bb1:
+    cf.br ^bb2
+  ^bb2:
+    cf.br ^bb1
+}
+
+// CHECK-LABEL:   @no_cycle_2_blocks
+// CHECK:           %[[VAL_0:.*]] = arith.constant 1 : i32
+// CHECK:           return %[[VAL_0]] : i32
+func.func @no_cycle_2_blocks() -> i32 {
+  cf.br ^bb1
+  ^bb1:
+    cf.br ^bb2
+  ^bb2:
+    cf.br ^bb3
+  ^bb3:
+    %ret = arith.constant 1 : i32
+    return %ret : i32
+}
+
+// CHECK-LABEL:   @cycle_4_blocks
+// CHECK:           cf.br ^bb1
+// CHECK:         ^bb1:
+// CHECK:           cf.br ^bb1
+func.func @cycle_4_blocks() {
+  cf.br ^bb1
+  ^bb1:
+    cf.br ^bb2
+  ^bb2:
+    cf.br ^bb3
+  ^bb3:
+    cf.br ^bb4
+  ^bb4:
+    cf.br ^bb1
+}
+
+// CHECK-LABEL:   @no_cycle_4_blocks
+// CHECK:           %[[VAL_0:.*]] = arith.constant 1 : i32
+// CHECK:           return %[[VAL_0]] : i32
+func.func @no_cycle_4_blocks() -> i32 {
+  cf.br ^bb1
+  ^bb1:
+    cf.br ^bb2
+  ^bb2:
+    cf.br ^bb3
+  ^bb3:
+    cf.br ^bb4
+  ^bb4:
+    cf.br ^bb5
+  ^bb5:
+    %ret = arith.constant 1 : i32
+    return %ret : i32
+}
+
+// CHECK-LABEL:   @delayed_3_cycle
+// CHECK:           cf.br ^bb1
+// CHECK:         ^bb1:
+// CHECK:           cf.br ^bb1
+func.func @delayed_3_cycle() {
+  cf.br ^bb1
+  ^bb1:
+    cf.br ^bb2
+  ^bb2:
+    cf.br ^bb3
+  ^bb3:
+    cf.br ^bb4
+  ^bb4:
+    cf.br ^bb5
+  ^bb5:
+    cf.br ^bb3
+}
+
+// CHECK-LABEL:   @cycle_1_block
+// CHECK:           cf.br ^bb1
+// CHECK:         ^bb1:
+// CHECK:           cf.br ^bb1
+func.func @cycle_1_block() {
+  cf.br ^bb1
+  ^bb1:
+    cf.br ^bb2
+  ^bb2:
+    cf.br ^bb2
+}
+
+// CHECK-LABEL:   @unsimplified_cycle_1
+// CHECK-SAME:      %[[ARG0:.*]]: i1) {
+// CHECK:           cf.br ^bb1
+// CHECK:         ^bb1:
+// CHECK:           cf.br ^bb1
+func.func @unsimplified_cycle_1(%c : i1) {
+  cf.cond_br %c, ^bb1, ^bb2
+  ^bb1:
----------------
matthias-springer wrote:

nit: Basic blocks should not be indented. (See other test cases in this file.)


https://github.com/llvm/llvm-project/pull/160783