Fix a DAGCombiner abort on an invalid shift count constant. This fixes PR3250.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61613 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4fb50e30dbeb5da0678dbf8b9e32059dacc14099..f1e43a90246381ac5bf7929eb5943152d7c0288e 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3277,6 +3277,8 @@ SDValue DAGCombiner::GetDemandedBits(SDValue V, const APInt &Mask) {
     if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(V.getOperand(1))) {
       // See if we can recursively simplify the LHS.
       unsigned Amt = RHSC->getZExtValue();
+      // Watch out for shift count overflow though.
+      if (Amt >= Mask.getBitWidth()) break;
       APInt NewMask = Mask << Amt;
       SDValue SimplifyLHS = GetDemandedBits(V.getOperand(0), NewMask);
       if (SimplifyLHS.getNode()) {

diff --git a/test/CodeGen/X86/pr3250.ll b/test/CodeGen/X86/pr3250.ll
new file mode 100644 (file)
index 0000000..dce154f
--- /dev/null
+++ b/test/CodeGen/X86/pr3250.ll
@@ -0,0 +1,17 @@
+; RUN: llvm-as < %s | llc -march=x86
+; PR3250
+
+declare i32 @safe_sub_func_short_u_u(i16 signext, i16 signext) nounwind
+
+define i32 @func_106(i32 %p_107) nounwind {
+entry:
+        %0 = tail call i32 (...)* @safe_div_(i32 %p_107, i32 1) nounwind       
+        ; <i32> [#uses=1]
+        %1 = lshr i32 %0, -9            ; <i32> [#uses=1]
+        %2 = trunc i32 %1 to i16                ; <i16> [#uses=1]
+        %3 = tail call i32 @safe_sub_func_short_u_u(i16 signext 1, i16 signext
+%2) nounwind             ; <i32> [#uses=0]
+        ret i32 undef
+}
+
+declare i32 @safe_div_(...)