[llvm-branch-commits] [llvm] 97edd8f - [JumpThreading] ProcessBranchOnXOR(): bailout if any pred ends in indirect branch (PR46857)

[Hans Wennborg via llvm-branch-commits]

Author: Roman Lebedev
Date: 2020-07-27T16:31:31+02:00
New Revision: 97edd8fdf06170fb5f7c60e7a2324b5e0491e492

URL: https://github.com/llvm/llvm-project/commit/97edd8fdf06170fb5f7c60e7a2324b5e0491e492
DIFF: https://github.com/llvm/llvm-project/commit/97edd8fdf06170fb5f7c60e7a2324b5e0491e492.diff

LOG: [JumpThreading] ProcessBranchOnXOR(): bailout if any pred ends in indirect branch (PR46857)

SplitBlockPredecessors() can not split blocks that have such terminators,
and in two other places we already ensure that we don't end up calling
SplitBlockPredecessors() on such blocks. Do so in one more place.

Fixes https://bugs.llvm.org/show_bug.cgi?id=46857

(cherry picked from commit 1da9834557cd4302a5183b8228ce063e69f82602)

Added: 
    llvm/test/Transforms/JumpThreading/pr46857-callbr.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 9d0500419a7f..2f379b7f6160 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1859,6 +1859,14 @@ bool JumpThreadingPass::ProcessBranchOnXOR(BinaryOperator *BO) {
     return true;
   }
 
+  // If any of predecessors end with an indirect goto, we can't change its
+  // destination. Same for CallBr.
+  if (any_of(BlocksToFoldInto, [](BasicBlock *Pred) {
+        return isa<IndirectBrInst>(Pred->getTerminator()) ||
+               isa<CallBrInst>(Pred->getTerminator());
+      }))
+    return false;
+
   // Try to duplicate BB into PredBB.
   return DuplicateCondBranchOnPHIIntoPred(BB, BlocksToFoldInto);
 }

diff  --git a/llvm/test/Transforms/JumpThreading/pr46857-callbr.ll b/llvm/test/Transforms/JumpThreading/pr46857-callbr.ll
new file mode 100644
index 000000000000..3de7d6265136
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/pr46857-callbr.ll
@@ -0,0 +1,52 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -jump-threading -S | FileCheck %s
+
+; CHECK-ALL-LABEL: @func(
+
+define i1 @func(i1 %arg, i32 %arg1, i1 %arg2) {
+; CHECK-LABEL: @func(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 [[ARG:%.*]], label [[BB3:%.*]], label [[BB4:%.*]]
+; CHECK:       bb3:
+; CHECK-NEXT:    [[I:%.*]] = icmp eq i32 [[ARG1:%.*]], 0
+; CHECK-NEXT:    br label [[BB7:%.*]]
+; CHECK:       bb4:
+; CHECK-NEXT:    callbr void asm sideeffect "", "X"(i8* blockaddress(@func, [[BB7]]))
+; CHECK-NEXT:    to label [[BB5:%.*]] [label %bb7]
+; CHECK:       bb5:
+; CHECK-NEXT:    br label [[BB7]]
+; CHECK:       bb7:
+; CHECK-NEXT:    [[I8:%.*]] = phi i1 [ [[I]], [[BB3]] ], [ [[ARG2:%.*]], [[BB5]] ], [ [[ARG2]], [[BB4]] ]
+; CHECK-NEXT:    [[I9:%.*]] = xor i1 [[I8]], [[ARG]]
+; CHECK-NEXT:    br i1 [[I9]], label [[BB11:%.*]], label [[BB11]]
+; CHECK:       bb11:
+; CHECK-NEXT:    ret i1 [[I9]]
+;
+bb:
+  br i1 %arg, label %bb3, label %bb4
+
+bb3:
+  %i = icmp eq i32 %arg1, 0
+  br label %bb7
+
+bb4:
+  callbr void asm sideeffect "", "X"(i8* blockaddress(@func, %bb6))
+  to label %bb5 [label %bb6]
+
+bb5:
+  br label %bb6
+
+bb6:
+  br label %bb7
+
+bb7:
+  %i8 = phi i1 [ %i, %bb3 ], [ %arg2, %bb6 ]
+  %i9 = xor i1 %i8, %arg
+  br i1 %i9, label %bb11, label %bb10
+
+bb10:
+  br label %bb11
+
+bb11:
+  ret i1 %i9
+}