[SDAG] Optimize unordered comparison in soft-float mode (patch by Anton Nadolskiy)

Current implementation handles unordered comparison poorly in soft-float mode. 
Consider (a ULE b) which is a <= b. It is lowered to (ledf2(a, b) <= 0 || unorddf2(a, b) != 0) (in general). We can do better job by lowering it to (__gtdf2(a, b) <= 0). 
Such replacement is true for other CMP's (ult, ugt, uge). In general, we just call same function as for ordered case but negate comparison against zero.
Differential Revision: http://reviews.llvm.org/D10804

llvm-svn: 242280

1 files changed, 31 insertions, 23 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index fbf651277c7..bacf8bee032 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -115,7 +115,6 @@ TargetLowering::makeLibCall(SelectionDAG &DAG,
   return LowerCallTo(CLI);
 }
 
-
 /// SoftenSetCCOperands - Soften the operands of a comparison.  This code is
 /// shared among BR_CC, SELECT_CC, and SETCC handlers.
 void TargetLowering::softenSetCCOperands(SelectionDAG &DAG, EVT VT,
@@ -127,6 +126,7 @@ void TargetLowering::softenSetCCOperands(SelectionDAG &DAG, EVT VT,
 
   // Expand into one or more soft-fp libcall(s).
   RTLIB::Libcall LC1 = RTLIB::UNKNOWN_LIBCALL, LC2 = RTLIB::UNKNOWN_LIBCALL;
+  bool ShouldInvertCC = false;
   switch (CCCode) {
   case ISD::SETEQ:
   case ISD::SETOEQ:
@@ -166,34 +166,38 @@ void TargetLowering::softenSetCCOperands(SelectionDAG &DAG, EVT VT,
     LC1 = (VT == MVT::f32) ? RTLIB::O_F32 :
           (VT == MVT::f64) ? RTLIB::O_F64 : RTLIB::O_F128;
     break;
-  default:
+  case ISD::SETONE:
+    // SETONE = SETOLT | SETOGT
+    LC1 = (VT == MVT::f32) ? RTLIB::OLT_F32 :
+          (VT == MVT::f64) ? RTLIB::OLT_F64 : RTLIB::OLT_F128;
+    LC2 = (VT == MVT::f32) ? RTLIB::OGT_F32 :
+          (VT == MVT::f64) ? RTLIB::OGT_F64 : RTLIB::OGT_F128;
+    break;
+  case ISD::SETUEQ:
     LC1 = (VT == MVT::f32) ? RTLIB::UO_F32 :
           (VT == MVT::f64) ? RTLIB::UO_F64 : RTLIB::UO_F128;
+    LC2 = (VT == MVT::f32) ? RTLIB::OEQ_F32 :
+          (VT == MVT::f64) ? RTLIB::OEQ_F64 : RTLIB::OEQ_F128;
+    break;
+  default:
+    // Invert CC for unordered comparisons
+    ShouldInvertCC = true;
     switch (CCCode) {
-    case ISD::SETONE:
-      // SETONE = SETOLT | SETOGT
-      LC1 = (VT == MVT::f32) ? RTLIB::OLT_F32 :
-            (VT == MVT::f64) ? RTLIB::OLT_F64 : RTLIB::OLT_F128;
-      // Fallthrough
-    case ISD::SETUGT:
-      LC2 = (VT == MVT::f32) ? RTLIB::OGT_F32 :
-            (VT == MVT::f64) ? RTLIB::OGT_F64 : RTLIB::OGT_F128;
-      break;
-    case ISD::SETUGE:
-      LC2 = (VT == MVT::f32) ? RTLIB::OGE_F32 :
-            (VT == MVT::f64) ? RTLIB::OGE_F64 : RTLIB::OGE_F128;
-      break;
     case ISD::SETULT:
-      LC2 = (VT == MVT::f32) ? RTLIB::OLT_F32 :
-            (VT == MVT::f64) ? RTLIB::OLT_F64 : RTLIB::OLT_F128;
+      LC1 = (VT == MVT::f32) ? RTLIB::OGE_F32 :
+            (VT == MVT::f64) ? RTLIB::OGE_F64 : RTLIB::OGE_F128;
       break;
     case ISD::SETULE:
-      LC2 = (VT == MVT::f32) ? RTLIB::OLE_F32 :
+      LC1 = (VT == MVT::f32) ? RTLIB::OGT_F32 :
+            (VT == MVT::f64) ? RTLIB::OGT_F64 : RTLIB::OGT_F128;
+      break;
+    case ISD::SETUGT:
+      LC1 = (VT == MVT::f32) ? RTLIB::OLE_F32 :
             (VT == MVT::f64) ? RTLIB::OLE_F64 : RTLIB::OLE_F128;
       break;
-    case ISD::SETUEQ:
-      LC2 = (VT == MVT::f32) ? RTLIB::OEQ_F32 :
-            (VT == MVT::f64) ? RTLIB::OEQ_F64 : RTLIB::OEQ_F128;
+    case ISD::SETUGE:
+      LC1 = (VT == MVT::f32) ? RTLIB::OLT_F32 :
+            (VT == MVT::f64) ? RTLIB::OLT_F64 : RTLIB::OLT_F128;
       break;
     default: llvm_unreachable("Do not know how to soften this setcc!");
     }
@@ -203,16 +207,20 @@ void TargetLowering::softenSetCCOperands(SelectionDAG &DAG, EVT VT,
   EVT RetVT = getCmpLibcallReturnType();
   SDValue Ops[2] = { NewLHS, NewRHS };
   NewLHS = makeLibCall(DAG, LC1, RetVT, Ops, 2, false/*sign irrelevant*/,
-                       dl).first;
+					   dl).first;
   NewRHS = DAG.getConstant(0, dl, RetVT);
+
   CCCode = getCmpLibcallCC(LC1);
+  if (ShouldInvertCC)
+    CCCode = getSetCCInverse(CCCode, /*isInteger=*/true);
+
   if (LC2 != RTLIB::UNKNOWN_LIBCALL) {
     SDValue Tmp = DAG.getNode(
         ISD::SETCC, dl,
         getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), RetVT),
         NewLHS, NewRHS, DAG.getCondCode(CCCode));
     NewLHS = makeLibCall(DAG, LC2, RetVT, Ops, 2, false/*sign irrelevant*/,
-                         dl).first;
+      dl).first;
     NewLHS = DAG.getNode(
         ISD::SETCC, dl,
         getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), RetVT),