[llvm] 6be1fd6 - [SimplifyCFG] FoldValueComparisonIntoPredecessors(): drop reachable errneous assert

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2021-01-07T18:05:04+03:00
New Revision: 6be1fd6b20f3418543a50ce9b04ab4a49585a7eb

URL: https://github.com/llvm/llvm-project/commit/6be1fd6b20f3418543a50ce9b04ab4a49585a7eb
DIFF: https://github.com/llvm/llvm-project/commit/6be1fd6b20f3418543a50ce9b04ab4a49585a7eb.diff

LOG: [SimplifyCFG] FoldValueComparisonIntoPredecessors(): drop reachable errneous assert

I have added it in d15d81c because it *seemed* correct, was holding
for all the tests so far, and was validating the fix added in the same
commit, but as David Major is pointing out (with a reproducer),
the assertion isn't really correct after all. So remove it.

Note that the d15d81c still fine.

Added: 
    llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-no-new-successors.ll

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 3fbc22a85be4..9aedb918ac32 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1261,7 +1261,6 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
       // Okay, at this point, we know which new successor Pred will get.  Make
       // sure we update the number of entries in the PHI nodes for these
       // successors.
-      assert(!NewSuccessors.empty() && "Should be adding some new successors.");
       for (const std::pair<BasicBlock *, int /*Num*/> &NewSuccessor :
            NewSuccessors) {
         for (auto I : seq(0, NewSuccessor.second)) {

diff  --git a/llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-no-new-successors.ll b/llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-no-new-successors.ll
new file mode 100644
index 000000000000..03490c9ac34b
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-no-new-successors.ll
@@ -0,0 +1,35 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -simplifycfg -simplifycfg-require-and-preserve-domtree=1 < %s | FileCheck %s
+
+define void @widget(i32 %arg) {
+; CHECK-LABEL: @widget(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i32 [[ARG:%.*]], 2
+; CHECK-NEXT:    br i1 [[SWITCH]], label [[BB2:%.*]], label [[INFLOOP:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    ret void
+; CHECK:       infloop:
+; CHECK-NEXT:    br label [[INFLOOP]]
+;
+bb:
+  %tmp = icmp eq i32 %arg, 0
+  br i1 %tmp, label %bb2, label %bb1
+
+bb1:                                              ; preds = %bb1
+  %tmp4 = icmp eq i32 %arg, 1
+  br i1 %tmp4, label %bb6, label %bb5
+
+bb5:                                              ; preds = %bb5, %bb5
+  switch i32 %arg, label %bb5 [
+  i32 0, label %bb9
+  ]
+
+bb2:
+  ret void
+
+bb6:                                              ; preds = %bb1
+  ret void
+
+bb9:                                              ; preds = %bb5
+  ret void
+}