[llvm] 6d036b8 - [JumpThreading] Avoid threadThroughTwoBasicBlocks when PredPred BB ends with indirectbranch

[Nikita Popov via llvm-commits]

Author: ChenYang Li
Date: 2022-07-08T09:29:17+02:00
New Revision: 6d036b83d1afcf49c1eed3dc455f6558282908eb

URL: https://github.com/llvm/llvm-project/commit/6d036b83d1afcf49c1eed3dc455f6558282908eb
DIFF: https://github.com/llvm/llvm-project/commit/6d036b83d1afcf49c1eed3dc455f6558282908eb.diff

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

Since we can't change the destination of indirectbr, so when
encounter indirectbr as PredPredBB terminator, we should pass it.

Differential Revision: https://reviews.llvm.org/D129193

Added: 
    llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll

Modified: 
    llvm/lib/Transforms/Scalar/JumpThreading.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index c441cf2799c23..b31eab50c5ecc 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -2169,6 +2169,9 @@ bool JumpThreadingPass::maybethreadThroughTwoBasicBlocks(BasicBlock *BB,
   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()) {

diff  --git a/llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll b/llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll
new file mode 100644
index 0000000000000..a2005600470d0
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/indirectbr-in-predpred.ll
@@ -0,0 +1,54 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S < %s -jump-threading | FileCheck %s
+
+define i1 @test1(i32 %0) #0 {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  PredPredBB1:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[TMP0:%.*]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 32, [[TMP0]]
+; CHECK-NEXT:    [[INDIRECT_GOTO_DEST:%.*]] = select i1 [[CMP]], i8* blockaddress(@test1, [[PREDBB1:%.*]]), i8* blockaddress(@test1, [[PREDPREDBB2:%.*]])
+; CHECK-NEXT:    indirectbr i8* [[INDIRECT_GOTO_DEST]], [label [[PREDBB1]], label %PredPredBB2]
+; CHECK:       PredPredBB2:
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ne i32 [[TMP0]], 1
+; CHECK-NEXT:    br i1 [[CMP1]], label [[PREDBB1]], label [[BB2:%.*]]
+; CHECK:       PredBB1:
+; CHECK-NEXT:    [[NUM:%.*]] = phi i32 [ 0, [[PREDPREDBB1:%.*]] ], [ [[TMP1]], [[PREDPREDBB2]] ]
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i32 [[TMP1]], 100
+; CHECK-NEXT:    br i1 [[CMP2]], label [[BB1:%.*]], label [[BB2]]
+; CHECK:       BB1:
+; CHECK-NEXT:    [[CMP3:%.*]] = icmp eq i32 [[NUM]], 0
+; CHECK-NEXT:    br i1 [[CMP3]], label [[BB2]], label [[BB3:%.*]]
+; CHECK:       BB2:
+; CHECK-NEXT:    [[TMP2:%.*]] = or i1 [[CMP]], true
+; CHECK-NEXT:    ret i1 [[TMP2]]
+; CHECK:       BB3:
+; CHECK-NEXT:    ret i1 true
+;
+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 }