[llvm] [LoopUnroll] Rotate loop to make it countable for runtime unrolling (PR #146540)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,99 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt --passes=loop-unroll -unroll-runtime-other-exit-predictable=1 -S %s | FileCheck %s
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @test(i64 %0) #0 {
+; CHECK-LABEL: define void @test(
+; CHECK-SAME: i64 [[TMP0:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[B1:%.*]] = icmp eq i64 [[TMP0]], 0
+; CHECK-NEXT:    br i1 [[B1]], label %[[AFTER:.*]], label %[[BODY_LR_PH:.*]]
+; CHECK:       [[BODY_LR_PH]]:
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 0, [[TMP0]]
+; CHECK-NEXT:    [[TMP2:%.*]] = freeze i64 [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = add i64 [[TMP2]], -1
+; CHECK-NEXT:    [[XTRAITER:%.*]] = and i64 [[TMP2]], 3
+; CHECK-NEXT:    [[LCMP_MOD:%.*]] = icmp ne i64 [[XTRAITER]], 0
+; CHECK-NEXT:    br i1 [[LCMP_MOD]], label %[[BODY_PROL_PREHEADER:.*]], label %[[BODY_PROL_LOOPEXIT:.*]]
+; CHECK:       [[BODY_PROL_PREHEADER]]:
+; CHECK-NEXT:    br label %[[BODY_PROL:.*]]
+; CHECK:       [[BODY_PROL]]:
+; CHECK-NEXT:    [[A2_PROL:%.*]] = phi i64 [ [[TMP0]], %[[BODY_PROL_PREHEADER]] ], [ [[A_PROL:%.*]], %[[HEADER_PROL:.*]] ]
+; CHECK-NEXT:    [[PROL_ITER:%.*]] = phi i64 [ 0, %[[BODY_PROL_PREHEADER]] ], [ [[PROL_ITER_NEXT:%.*]], %[[HEADER_PROL]] ]
+; CHECK-NEXT:    [[C_PROL:%.*]] = add i64 [[A2_PROL]], 1
+; CHECK-NEXT:    [[D_PROL:%.*]] = load i32, ptr addrspace(1) null, align 4
+; CHECK-NEXT:    [[E_PROL:%.*]] = icmp eq i32 [[D_PROL]], 0
+; CHECK-NEXT:    br i1 [[E_PROL]], label %[[END_LOOPEXIT3:.*]], label %[[HEADER_PROL]]
+; CHECK:       [[HEADER_PROL]]:
+; CHECK-NEXT:    [[A_PROL]] = phi i64 [ [[C_PROL]], %[[BODY_PROL]] ]
+; CHECK-NEXT:    [[B_PROL:%.*]] = icmp eq i64 [[A_PROL]], 0
+; CHECK-NEXT:    [[PROL_ITER_NEXT]] = add i64 [[PROL_ITER]], 1
+; CHECK-NEXT:    [[PROL_ITER_CMP:%.*]] = icmp ne i64 [[PROL_ITER_NEXT]], [[XTRAITER]]
+; CHECK-NEXT:    br i1 [[PROL_ITER_CMP]], label %[[BODY_PROL]], label %[[BODY_PROL_LOOPEXIT_UNR_LCSSA:.*]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK:       [[BODY_PROL_LOOPEXIT_UNR_LCSSA]]:
+; CHECK-NEXT:    [[A2_UNR_PH:%.*]] = phi i64 [ [[A_PROL]], %[[HEADER_PROL]] ]
+; CHECK-NEXT:    br label %[[BODY_PROL_LOOPEXIT]]
+; CHECK:       [[BODY_PROL_LOOPEXIT]]:
+; CHECK-NEXT:    [[A2_UNR:%.*]] = phi i64 [ [[TMP0]], %[[BODY_LR_PH]] ], [ [[A2_UNR_PH]], %[[BODY_PROL_LOOPEXIT_UNR_LCSSA]] ]
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp ult i64 [[TMP3]], 3
+; CHECK-NEXT:    br i1 [[TMP4]], label %[[HEADER_AFTER_CRIT_EDGE:.*]], label %[[BODY_LR_PH_NEW:.*]]
+; CHECK:       [[BODY_LR_PH_NEW]]:
+; CHECK-NEXT:    br label %[[BODY:.*]]
+; CHECK:       [[HEADER:.*]]:
+; CHECK-NEXT:    br i1 false, label %[[END_LOOPEXIT:.*]], label %[[HEADER_1:.*]]
+; CHECK:       [[HEADER_1]]:
+; CHECK-NEXT:    br i1 false, label %[[END_LOOPEXIT]], label %[[HEADER_2:.*]]
+; CHECK:       [[HEADER_2]]:
+; CHECK-NEXT:    [[C_7:%.*]] = add i64 [[A2:%.*]], 4
+; CHECK-NEXT:    br i1 false, label %[[END_LOOPEXIT]], label %[[HEADER_3:.*]]
+; CHECK:       [[HEADER_3]]:
+; CHECK-NEXT:    [[B_7:%.*]] = icmp eq i64 [[C_7]], 0
+; CHECK-NEXT:    br i1 [[B_7]], label %[[HEADER_AFTER_CRIT_EDGE_UNR_LCSSA:.*]], label %[[BODY]]
+; CHECK:       [[BODY]]:
+; CHECK-NEXT:    [[A2]] = phi i64 [ [[A2_UNR]], %[[BODY_LR_PH_NEW]] ], [ [[C_7]], %[[HEADER_3]] ]
+; CHECK-NEXT:    [[D:%.*]] = load i32, ptr addrspace(1) null, align 4
+; CHECK-NEXT:    [[E:%.*]] = icmp eq i32 [[D]], 0
+; CHECK-NEXT:    br i1 [[E]], label %[[END_LOOPEXIT]], label %[[HEADER]]
+; CHECK:       [[END_LOOPEXIT]]:
+; CHECK-NEXT:    br label %[[END:.*]]
+; CHECK:       [[END_LOOPEXIT3]]:
+; CHECK-NEXT:    br label %[[END]]
+; CHECK:       [[END]]:
+; CHECK-NEXT:    ret void
+; CHECK:       [[HEADER_AFTER_CRIT_EDGE_UNR_LCSSA]]:
+; CHECK-NEXT:    br label %[[HEADER_AFTER_CRIT_EDGE]]
+; CHECK:       [[HEADER_AFTER_CRIT_EDGE]]:
+; CHECK-NEXT:    br label %[[AFTER]]
+; CHECK:       [[AFTER]]:
+; CHECK-NEXT:    call void @foo(i32 0)
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %header
+
+header:
+  %a = phi i64 [ %0, %entry ], [ %c, %body ]
+  %b = icmp eq i64 %a, 0
+  br i1 %b, label %after, label %body
+
+body:
+  %c = add i64 %a, 1
+  %d = load i32, ptr addrspace(1) null, align 4
----------------
fhahn wrote:

Please avoid immediate UB in tests, better add a pointer argument to use here.

https://github.com/llvm/llvm-project/pull/146540