[llvm] 5fb58d4 - [Test] Add Loop Deletion test with irreducible CFG

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2021-05-26T18:40:14+07:00
New Revision: 5fb58d45989d63c2deee1c901c3d02b6cf01a067

URL: https://github.com/llvm/llvm-project/commit/5fb58d45989d63c2deee1c901c3d02b6cf01a067
DIFF: https://github.com/llvm/llvm-project/commit/5fb58d45989d63c2deee1c901c3d02b6cf01a067.diff

LOG: [Test] Add Loop Deletion test with irreducible CFG

Authored by Mikael Holmén. It demonstrated miscompile on irreducible
CFG with patch "[LoopDeletion] Break backedge if we can prove that the loop is exited on 1st iteration".
The patch is reverted. Checking in the test to make sure this bug
does not return.

Added: 
    llvm/test/Transforms/LoopDeletion/irreducible-cfg.ll

Modified: 
    

Removed: 
    


################################################################################
diff  --git a/llvm/test/Transforms/LoopDeletion/irreducible-cfg.ll b/llvm/test/Transforms/LoopDeletion/irreducible-cfg.ll
new file mode 100644
index 000000000000..b0d34bb3e249
--- /dev/null
+++ b/llvm/test/Transforms/LoopDeletion/irreducible-cfg.ll
@@ -0,0 +1,69 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -loop-deletion -S | FileCheck %s
+; RUN: opt < %s -passes='loop(loop-deletion)' -S | FileCheck %s
+
+; Make sure we do not get the miscompile on this test with irreducible CFG.
+define i16 @test(i16 %j, i16 %k, i16 %recurs) {                 ; If we have %j: 1, %k: 1, %recurs: 0
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TOBOOL_NOT:%.*]] = icmp eq i16 [[RECURS:%.*]], 0
+; CHECK-NEXT:    br i1 [[TOBOOL_NOT]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[CALL:%.*]] = tail call i16 @test(i16 0, i16 0, i16 0)
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.end:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i16 [[J:%.*]], 0
+; CHECK-NEXT:    br label [[BB2:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[K_ADDR_0:%.*]] = phi i16 [ [[K:%.*]], [[IF_END]] ], [ [[K_ADDR_2:%.*]], [[BB12:%.*]] ]
+; CHECK-NEXT:    [[RESULT_0:%.*]] = phi i16 [ 0, [[IF_END]] ], [ 20, [[BB12]] ]
+; CHECK-NEXT:    br i1 [[CMP]], label [[BB12]], label [[BB4:%.*]]
+; CHECK:       bb4:
+; CHECK-NEXT:    [[K_ADDR_1:%.*]] = phi i16 [ [[K_ADDR_0]], [[BB2]] ], [ [[K_ADDR_2]], [[BB12]] ]
+; CHECK-NEXT:    [[X_1:%.*]] = phi i16 [ 0, [[BB2]] ], [ 1, [[BB12]] ]
+; CHECK-NEXT:    [[RESULT_1:%.*]] = phi i16 [ [[RESULT_0]], [[BB2]] ], [ 10, [[BB12]] ]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i16 [[K_ADDR_1]], 0
+; CHECK-NEXT:    br i1 [[CMP2]], label [[BB13:%.*]], label [[BB12]]
+; CHECK:       bb12:
+; CHECK-NEXT:    [[K_ADDR_2]] = phi i16 [ [[K_ADDR_0]], [[BB2]] ], [ 0, [[BB4]] ]
+; CHECK-NEXT:    [[X_2:%.*]] = phi i16 [ 1, [[BB2]] ], [ [[X_1]], [[BB4]] ]
+; CHECK-NEXT:    [[CMP5:%.*]] = icmp eq i16 [[X_2]], 0
+; CHECK-NEXT:    br i1 [[CMP5]], label [[BB2]], label [[BB4]]
+; CHECK:       bb13:
+; CHECK-NEXT:    [[RESULT_1_LCSSA:%.*]] = phi i16 [ [[RESULT_1]], [[BB4]] ]
+; CHECK-NEXT:    ret i16 [[RESULT_1_LCSSA]]
+;
+entry:
+  %tobool.not = icmp eq i16 %recurs, 0                          ; 1
+  br i1 %tobool.not, label %if.end, label %if.then              ; -> if.end
+
+if.then:                                          ; preds = %entry
+  %call = tail call i16 @test(i16 0, i16 0, i16 0)
+  br label %if.end
+
+if.end:                                           ; preds = %if.then, %entry
+  %cmp = icmp eq i16 %j, 0                                      ; 0
+  br label %bb2                                                 ; -> bb2
+
+bb2:                                              ; preds = %bb12, %if.end
+  %k.addr.0 = phi i16 [ %k, %if.end ], [ %k.addr.2, %bb12 ]     ; 1
+  %result.0 = phi i16 [ 0, %if.end ], [ 20, %bb12 ]             ; 0
+  br i1 %cmp, label %bb12, label %bb4                           ; %cmp: 0 -> bb4
+
+bb4:                                              ; preds = %bb12, %bb2
+  %k.addr.1 = phi i16 [ %k.addr.0, %bb2 ], [ %k.addr.2, %bb12 ] ; 1
+  %x.1 = phi i16 [ 0, %bb2 ], [ 1, %bb12 ]                      ; 0
+  %result.1 = phi i16 [ %result.0, %bb2 ], [ 10, %bb12 ]
+  %cmp2 = icmp eq i16 %k.addr.1, 0                              ; 0
+  br i1 %cmp2, label %bb13, label %bb12                         ; -> bb12
+
+bb12:                                             ; preds = %bb4, %bb2
+  %k.addr.2 = phi i16 [ %k.addr.0, %bb2 ], [ 0, %bb4 ]          ; 0
+  %x.2 = phi i16 [ 1, %bb2 ], [ %x.1, %bb4 ]                    ; 0
+  %cmp5 = icmp eq i16 %x.2, 0                                   ; 1
+  br i1 %cmp5, label %bb2, label %bb4                           ; -> bb2
+
+bb13:                                             ; preds = %bb4
+  %result.1.lcssa = phi i16 [ %result.1, %bb4 ]
+  ret i16 %result.1.lcssa
+}