Compile:

int %test(ulong *%tmp) {
        %tmp = load ulong* %tmp         ; <ulong> [#uses=1]
        %tmp.mask = shr ulong %tmp, ubyte 50            ; <ulong> [#uses=1]
        %tmp.mask = cast ulong %tmp.mask to ubyte
        %tmp2 = and ubyte %tmp.mask, 3          ; <ubyte> [#uses=1]
        %tmp2 = cast ubyte %tmp2 to int         ; <int> [#uses=1]
        ret int %tmp2
}

to:

_test:
        movl 4(%esp), %eax
        movl 4(%eax), %eax
        shrl $18, %eax
        andl $3, %eax
        ret

instead of:

_test:
        movl 4(%esp), %eax
        movl 4(%eax), %eax
        shrl $18, %eax
        # TRUNCATE movb %al, %al
        andb $3, %al
        movzbl %al, %eax
        ret


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30558 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 045a61d753..2f68106804 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1831,6 +1831,20 @@ SDOperand DAGCombiner::visitZERO_EXTEND(SDNode *N) {
     return DAG.getZeroExtendInReg(Op, N0.getValueType());
   }
   
+  // fold (zext (and (trunc x), cst)) -> (and x, cst).
+  if (N0.getOpcode() == ISD::AND &&
+      N0.getOperand(0).getOpcode() == ISD::TRUNCATE &&
+      N0.getOperand(1).getOpcode() == ISD::Constant) {
+    SDOperand X = N0.getOperand(0).getOperand(0);
+    if (X.getValueType() < VT) {
+      X = DAG.getNode(ISD::ANY_EXTEND, VT, X);
+    } else if (X.getValueType() > VT) {
+      X = DAG.getNode(ISD::TRUNCATE, VT, X);
+    }
+    uint64_t Mask = cast<ConstantSDNode>(N0.getOperand(1))->getValue();
+    return DAG.getNode(ISD::AND, VT, X, DAG.getConstant(Mask, VT));
+  }
+  
   // fold (zext (load x)) -> (zext (truncate (zextload x)))
   if (N0.getOpcode() == ISD::LOAD && N0.hasOneUse() &&
       (!AfterLegalize||TLI.isOperationLegal(ISD::ZEXTLOAD, N0.getValueType()))){