Compile:

int test3(int a, int b) { return (a < 0) ? a : 0; }

to:

_test3:
        srawi r2, r3, 31
        and r3, r2, r3
        blr

instead of:

_test3:
        cmpwi cr0, r3, 1
        li r2, 0
        blt cr0, LBB2_2 ;entry
LBB2_1: ;entry
        mr r3, r2
LBB2_2: ;entry
        blr

This implements: PowerPC/select_lt0.ll:seli32_a_a

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30517 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index bcbac950f4abe5b7148336a701e8ca4c8a25bbfc..43028a80c2e96668af13e1d6edea34baa2ac3035 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3168,7 +3168,6 @@ SDOperand DAGCombiner::SimplifySelectCC(SDOperand N0, SDOperand N1,
                                         ISD::CondCode CC) {
   
   MVT::ValueType VT = N2.getValueType();
-  //ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0.Val);
   ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.Val);
   ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2.Val);
   ConstantSDNode *N3C = dyn_cast<ConstantSDNode>(N3.Val);
@@ -3204,9 +3203,11 @@ SDOperand DAGCombiner::SimplifySelectCC(SDOperand N0, SDOperand N1,
   
   // Check to see if we can perform the "gzip trick", transforming
   // select_cc setlt X, 0, A, 0 -> and (sra X, size(X)-1), A
-  if (N1C && N1C->isNullValue() && N3C && N3C->isNullValue() &&
+  if (N1C && N3C && N3C->isNullValue() && CC == ISD::SETLT &&
       MVT::isInteger(N0.getValueType()) && 
-      MVT::isInteger(N2.getValueType()) && CC == ISD::SETLT) {
+      MVT::isInteger(N2.getValueType()) && 
+      (N1C->isNullValue() ||                    // (a < 0) ? b : 0
+       (N1C->getValue() == 1 && N0 == N2))) {   // (a < 1) ? a : 0
     MVT::ValueType XType = N0.getValueType();
     MVT::ValueType AType = N2.getValueType();
     if (XType >= AType) {