InstCombine: Don't assume DataLayout is always available

We tried to get the result of DataLayout::getLargestLegalIntTypeSize but
we didn't have a DataLayout.  This resulted in opt crashing.

This fixes PR21651.

llvm-svn: 222645

2 files changed, 22 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 292c20678ec..5eee15f6489 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2095,7 +2095,8 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
   // the largest legal integer type. We need to be conservative here since
   // x86 generates redundant zero-extenstion instructions if the operand is
   // truncated to i8 or i16.
-  if (BitWidth > NewWidth && NewWidth >= DL->getLargestLegalIntTypeSize()) {
+  if (DL && BitWidth > NewWidth &&
+      NewWidth >= DL->getLargestLegalIntTypeSize()) {
     IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth);
     Builder->SetInsertPoint(&SI);
     Value *NewCond = Builder->CreateTrunc(SI.getCondition(), Ty, "trunc");
diff --git a/llvm/test/Transforms/InstCombine/pr21651.ll b/llvm/test/Transforms/InstCombine/pr21651.ll
new file mode 100644
index 00000000000..914785f329a
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/pr21651.ll
@@ -0,0 +1,20 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define void @PR21651() {
+  switch i2 0, label %out [
+    i2 0, label %out
+    i2 1, label %out
+  ]
+
+out:
+  ret void
+}
+
+; CHECK-LABEL: define void @PR21651(
+; CHECK:   switch i2 0, label %out [
+; CHECK:     i2 0, label %out
+; CHECK:     i2 1, label %out
+; CHECK:   ]
+; CHECK: out:                                              ; preds = %0, %0, %0
+; CHECK:   ret void
+; CHECK: }