fix an infinite loop in reassociate building emacs.

llvm-svn: 92679

2 files changed, 19 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 564036bba3e..f2a8633f97a 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -932,6 +932,10 @@ void Reassociate::ReassociateBB(BasicBlock *BB) {
     if (BI->getOpcode() == Instruction::Sub) {
       if (ShouldBreakUpSubtract(BI)) {
         BI = BreakUpSubtract(BI, ValueRankMap);
+        // Reset the BBI iterator in case BreakUpSubtract changed the
+        // instruction it points to.
+        BBI = BI;
+        ++BBI;
         MadeChange = true;
       } else if (BinaryOperator::isNeg(BI)) {
         // Otherwise, this is a negation.  See if the operand is a multiply tree
diff --git a/llvm/test/Transforms/Reassociate/crash.ll b/llvm/test/Transforms/Reassociate/crash.ll
new file mode 100644
index 00000000000..12f8a376fdb
--- /dev/null
+++ b/llvm/test/Transforms/Reassociate/crash.ll
@@ -0,0 +1,15 @@
+; RUN: opt -reassociate -disable-output %s
+
+
+; rdar://7507855
+define fastcc i32 @test() nounwind {
+entry:
+  %cond = select i1 undef, i32 1, i32 -1          ; <i32> [#uses=2]
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %sub889 = sub i32 undef, undef                  ; <i32> [#uses=1]
+  %sub891 = sub i32 %sub889, %cond                ; <i32> [#uses=0]
+  %add896 = sub i32 0, %cond                      ; <i32> [#uses=0]
+  ret i32 undef
+}