Fix for logic in combineExtract()

Author: JonPsson1

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

@@ -6586,13 +6586,12 @@ SDValue SystemZTargetLowering::combineExtract(const SDLoc &DL, EVT ResVT,
   // The number of bytes being extracted.
   unsigned BytesPerElement = VecVT.getVectorElementType().getStoreSize();
 
-  for (;;) {
+  while (canTreatAsByteVector(Op.getValueType())) {
     unsigned Opcode = Op.getOpcode();
     if (Opcode == ISD::BITCAST)
       // Look through bitcasts.
       Op = Op.getOperand(0);
-    else if ((Opcode == ISD::VECTOR_SHUFFLE || Opcode == SystemZISD::SPLAT) &&
-             canTreatAsByteVector(Op.getValueType())) {
+    else if (Opcode == ISD::VECTOR_SHUFFLE || Opcode == SystemZISD::SPLAT) {
       // Get a VPERM-like permute mask and see whether the bytes covered
       // by the extracted element are a contiguous sequence from one
       // source operand.
@@ -6614,8 +6613,7 @@ SDValue SystemZTargetLowering::combineExtract(const SDLoc &DL, EVT ResVT,
       Index = Byte / BytesPerElement;
       Op = Op.getOperand(unsigned(First) / Bytes.size());
       Force = true;
-    } else if (Opcode == ISD::BUILD_VECTOR &&
-               canTreatAsByteVector(Op.getValueType())) {
+    } else if (Opcode == ISD::BUILD_VECTOR) {
       // We can only optimize this case if the BUILD_VECTOR elements are
       // at least as wide as the extracted value.
       EVT OpVT = Op.getValueType();
@@ -6644,7 +6642,6 @@ SDValue SystemZTargetLowering::combineExtract(const SDLoc &DL, EVT ResVT,
     } else if ((Opcode == ISD::SIGN_EXTEND_VECTOR_INREG ||
                 Opcode == ISD::ZERO_EXTEND_VECTOR_INREG ||
                 Opcode == ISD::ANY_EXTEND_VECTOR_INREG) &&
-               canTreatAsByteVector(Op.getValueType()) &&
                canTreatAsByteVector(Op.getOperand(0).getValueType())) {
       // Make sure that only the unextended bits are significant.
       EVT ExtVT = Op.getValueType();

llvm/test/CodeGen/SystemZ/DAGCombine_extract_vector_elt.ll

@@ -0,0 +1,20 @@
+; RUN: llc -mtriple=s390x-linux-gnu -mcpu=z16 < %s  | FileCheck %s
+;
+; Check that DAGCombiner doesn't crash in SystemZ combineExtract()
+; when handling EXTRACT_VECTOR_ELT with a vector of i1:s.
+
+define i32 @fun(i32 %arg) {
+; CHECK-LABEL: fun:
+entry:
+  %cc = icmp eq i32 %arg, 0
+  br label %loop
+
+loop:
+  %P = phi <128 x i1> [ zeroinitializer, %entry ], [ bitcast (<2 x i64> <i64 3, i64 3> to <128 x i1>), %loop ]
+  br i1 %cc, label %exit, label %loop
+
+exit:
+  %E = extractelement <128 x i1> %P, i64 0
+  %Res = zext i1 %E to i32
+  ret i32 %Res
+}