[DAGCombine] Handle out of range EXTRACT_VECTOR_ELT indices

Handle this in DAGCombiner::visitEXTRACT_VECTOR_ELT the same as we already do in SelectionDAG::getNode and use APInt instead of getZExtValue.

This should also fix oss-fuzz #4910

llvm-svn: 321767

3 files changed, 23 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 81bff4d7eef..2b44e4fa93c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -14200,6 +14200,10 @@ SDValue DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
   SDValue EltNo = N->getOperand(1);
   ConstantSDNode *ConstEltNo = dyn_cast<ConstantSDNode>(EltNo);
 
+  // extract_vector_elt of out-of-bounds element -> UNDEF
+  if (ConstEltNo && ConstEltNo->getAPIntValue().uge(VT.getVectorNumElements()))
+    return DAG.getUNDEF(NVT);
+
   // extract_vector_elt (build_vector x, y), 1 -> y
   if (ConstEltNo &&
       InVec.getOpcode() == ISD::BUILD_VECTOR &&
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 4c8b63d2f23..7e99863b1ee 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4453,7 +4453,7 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
       return getUNDEF(VT);
 
     // EXTRACT_VECTOR_ELT of out-of-bounds element is an UNDEF
-    if (N2C && N2C->getZExtValue() >= N1.getValueType().getVectorNumElements())
+    if (N2C && N2C->getAPIntValue().uge(N1.getValueType().getVectorNumElements()))
       return getUNDEF(VT);
 
     // EXTRACT_VECTOR_ELT of CONCAT_VECTORS is often formed while lowering is
diff --git a/llvm/test/CodeGen/X86/extract-insert.ll b/llvm/test/CodeGen/X86/extract-insert.ll
new file mode 100644
index 00000000000..823390e86d1
--- /dev/null
+++ b/llvm/test/CodeGen/X86/extract-insert.ll
@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=i686-unknown-unknown -mattr=+sse2 | FileCheck %s --check-prefix=CHECK --check-prefix=X86
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=+sse2 | FileCheck %s --check-prefix=CHECK --check-prefix=X64
+
+define i32 @extractelt_undef_insertelt(i32 %x, i32 %y) {
+; X86-LABEL: extractelt_undef_insertelt:
+; X86:       # %bb.0:
+; X86-NEXT:    retl
+;
+; X64-LABEL: extractelt_undef_insertelt:
+; X64:       # %bb.0:
+; X64-NEXT:    retq
+  %b = insertelement <4 x i32> zeroinitializer, i32 %x, i64 3
+  %c = icmp uge i32 %y, %y
+  %d = extractelement <4 x i32> %b, i1 %c
+  ret i32 %d
+}
+