From 8840c94a338097d8e5ac4556256040baf23b0526 Mon Sep 17 00:00:00 2001
From: Max Kazantsev <mkazantsev@azul.com>
Date: Fri, 11 Jun 2021 18:40:44 +0700
Subject: [PATCH] [Test] One more elaborate test with selects for loop deletion

---
 .../LoopDeletion/eval_first_iteration.ll      | 52 ++++++++++++++++++-
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll b/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll
index 252d4ab43d49..cb2f874306f0 100644
--- a/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll
+++ b/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll
@@ -725,8 +725,8 @@ failure:
 }
 
 ; TODO: We can break the backedge here.
-define i32 @test_switch(i32 %limit) {
-; CHECK-LABEL: @test_switch(
+define i32 @test_select(i32 %limit) {
+; CHECK-LABEL: @test_select(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[LOOP_GUARD:%.*]] = icmp sgt i32 [[LIMIT:%.*]], 0
 ; CHECK-NEXT:    br i1 [[LOOP_GUARD]], label [[LOOP_PREHEADER:%.*]], label [[FAILURE:%.*]]
@@ -766,3 +766,51 @@ done:                                             ; preds = %backedge
 failure:
   unreachable
 }
+
+; TODO: We can break the backedge here.
+define i32 @test_select_const(i32 %x) {
+; CHECK-LABEL: @test_select_const(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[SUM:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[SUM_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 4, [[SUM]]
+; CHECK-NEXT:    [[IS_POSITIVE:%.*]] = icmp sgt i32 [[SUB]], 0
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[IS_POSITIVE]], i32 [[SUB]], i32 [[X:%.*]]
+; CHECK-NEXT:    [[SEL_COND:%.*]] = icmp sgt i32 [[SEL]], 0
+; CHECK-NEXT:    br i1 [[SEL_COND]], label [[BACKEDGE]], label [[IF_FALSE:%.*]]
+; CHECK:       if.false:
+; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK:       backedge:
+; CHECK-NEXT:    [[MERGE_PHI:%.*]] = phi i32 [ 0, [[IF_FALSE]] ], [ [[SUB]], [[LOOP]] ]
+; CHECK-NEXT:    [[SUM_NEXT]] = add i32 [[SUM]], [[MERGE_PHI]]
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ne i32 [[SUM_NEXT]], 4
+; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]]
+; CHECK:       done:
+; CHECK-NEXT:    [[SUM_NEXT_LCSSA:%.*]] = phi i32 [ [[SUM_NEXT]], [[BACKEDGE]] ]
+; CHECK-NEXT:    ret i32 [[SUM_NEXT_LCSSA]]
+;
+entry:
+  br label %loop
+
+loop:                                             ; preds = %backedge, %entry
+  %sum = phi i32 [ 0, %entry ], [ %sum.next, %backedge ]
+  %sub = sub i32 4, %sum
+  %is.positive = icmp sgt i32 %sub, 0
+  %sel = select i1 %is.positive, i32 %sub, i32 %x
+  %sel.cond = icmp sgt i32 %sel, 0
+  br i1 %sel.cond, label %backedge, label %if.false
+
+if.false:                                         ; preds = %loop
+  br label %backedge
+
+backedge:                                         ; preds = %if.false, %loop
+  %merge.phi = phi i32 [ 0, %if.false ], [ %sub, %loop ]
+  %sum.next = add i32 %sum, %merge.phi
+  %loop.cond = icmp ne i32 %sum.next, 4
+  br i1 %loop.cond, label %loop, label %done
+
+done:                                             ; preds = %backedge
+  %sum.next.lcssa = phi i32 [ %sum.next, %backedge ]
+  ret i32 %sum.next.lcssa
+}