Revert revision: 171467. This transformation is incorrect and makes some tests fail. Original message:

Simplified TRUNCATE operation that comes after SETCC. It is possible since SETCC result is 0 or -1.
Added a test.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171468 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 3 insertions, 35 deletions

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 9a553d6..eca63f8 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -14661,29 +14661,12 @@ static SDValue PerformShuffleCombine(SDNode *N, SelectionDAG &DAG,
   return EltsFromConsecutiveLoads(VT, Elts, dl, DAG);
 }
 
-/// PerformTruncateCombine - In some cases a sequence with "truncate"
-/// operation may be simplified.
+/// PerformTruncateCombine - Converts truncate operation to
+/// a sequence of vector shuffle operations.
+/// It is possible when we truncate 256-bit vector to 128-bit vector
 static SDValue PerformTruncateCombine(SDNode *N, SelectionDAG &DAG,
                                       TargetLowering::DAGCombinerInfo &DCI,
                                       const X86Subtarget *Subtarget)  {
-  EVT VT = N->getValueType(0);
-  if (DCI.isBeforeLegalize() || !VT.isVector())
-    return SDValue();
-
-  SDValue In = N->getOperand(0);
-  // Optimize the sequence setcc -> truncate
-  if (In.getOpcode() == ISD::SETCC) {
-    DebugLoc DL = N->getDebugLoc();
-    EVT InVT = In.getValueType();
-
-    // The vector element is all ones or all zero. Just take a half of it.
-    EVT HalfVT = EVT::getVectorVT(*DAG.getContext(), InVT.getScalarType(),
-                                  InVT.getVectorNumElements()/2);
-    SDValue HalfVec = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, HalfVT, In,
-                                  DAG.getIntPtrConstant(0));
-    assert(HalfVT.getSizeInBits() == VT.getSizeInBits());
-    return DAG.getNode(ISD::BITCAST, DL, VT, HalfVec);
-  }
   return SDValue();
 }
 
diff --git a/test/CodeGen/X86/avx-trunc.ll b/test/CodeGen/X86/avx-trunc.ll
index aa186a0..d007736 100755
--- a/test/CodeGen/X86/avx-trunc.ll
+++ b/test/CodeGen/X86/avx-trunc.ll
@@ -13,18 +13,3 @@ define <8 x i16> @trunc_32_16(<8 x i32> %A) nounwind uwtable readnone ssp{
   ret <8 x i16>%B
 }
 
-define <8 x i16> @trunc_after_setcc(<8 x float> %a, <8 x float> %b, <8 x float> %c, <8 x float> %d) {
-; CHECK: trunc_after_setcc
-; CHECK: vcmpltps
-; CHECK-NOT: vextract
-; CHECK: vcmpltps
-; CHECK-NEXT: vandps
-; CHECK-NEXT: vandps
-; CHECK: ret
-  %res1 = fcmp olt <8 x float> %a, %b
-  %res2 = fcmp olt <8 x float> %c, %d
-  %andr = and <8 x i1>%res1, %res2
-  %ex = zext <8 x i1> %andr to <8 x i16>
-  ret <8 x i16>%ex
-}
-