[PATCH] D129193: [JumpThreading] Avoid threadThroughTwoBasicBlocks when PredPred BB ends with indirectbranch

[ChenYang Li via Phabricator via llvm-commits]

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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129193

Files:
  llvm/lib/Transforms/Scalar/JumpThreading.cpp
  llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll


Index: llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll
@@ -0,0 +1,33 @@
+; RUN: opt -S < %s -jump-threading | FileCheck %s
+
+; CHECK: %indirect.goto.dest = select i1 %cmp, i8* blockaddress(@test1, %PredBB1), i8* blockaddress(@test1, %PredPredBB2)
+; CHECK: indirectbr i8* %indirect.goto.dest, [label %PredBB1, label %PredPredBB2]
+define i1 @test1(i32 %0) #0 {
+PredPredBB1:
+  %cmp = icmp ne i32 %0, 0
+  %1 = add i32 32, %0
+  %indirect.goto.dest = select i1 %cmp, i8* blockaddress(@test1, %PredBB1), i8* blockaddress(@test1, %PredPredBB2)
+  indirectbr i8* %indirect.goto.dest, [label %PredBB1, label %PredPredBB2]
+
+PredPredBB2:                                      ; preds = %PredPredBB1
+  %cmp1 = icmp ne i32 %0, 1
+  br i1 %cmp1, label %PredBB1, label %BB2
+
+PredBB1:                                          ; preds = %PredPredBB2, %PredPredBB1
+  %num = phi i32 [ 0, %PredPredBB1 ], [ %1, %PredPredBB2 ]
+  %cmp2 = icmp eq i32 %1, 100
+  br i1 %cmp2, label %BB1, label %BB2
+
+BB1:                                              ; preds = %PredBB1
+  %cmp3 = icmp eq i32 %num, 0
+  br i1 %cmp3, label %BB2, label %BB3
+
+BB2:                                              ; preds = %BB1, %PredBB1, %PredPredBB2
+  %2 = or i1 %cmp, true
+  ret i1 %2
+
+BB3:                                              ; preds = %BB1
+  ret i1 true
+}
+
+attributes #0 = { nounwind }
Index: llvm/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -2173,6 +2173,9 @@
   BasicBlock *ZeroPred = nullptr;
   BasicBlock *OnePred = nullptr;
   for (BasicBlock *P : predecessors(PredBB)) {
+    // If PredPred ends with IndirectBrInst, we can't handle it.
+    if (isa<IndirectBrInst>(P->getTerminator()))
+      continue;
     if (ConstantInt *CI = dyn_cast_or_null<ConstantInt>(
             evaluateOnPredecessorEdge(BB, P, Cond))) {
       if (CI->isZero()) {


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