[PATCH] SelectionDAG: Expand i64 = FP_TO_SINT i32

[Tom Stellard]

---
 lib/CodeGen/SelectionDAG/LegalizeDAG.cpp | 59 ++++++++++++++++++++++++++++++++
 lib/Target/R600/AMDGPUISelLowering.cpp   |  2 ++
 test/CodeGen/R600/fp_to_sint_i64.ll      | 12 +++++++
 3 files changed, 73 insertions(+)
 create mode 100644 test/CodeGen/R600/fp_to_sint_i64.ll

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 745ed4a..13c71fc 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -3128,6 +3128,65 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
                                 Node->getOperand(0), Node->getValueType(0), dl);
     Results.push_back(Tmp1);
     break;
+  case ISD::FP_TO_SINT: {
+    EVT VT = Node->getOperand(0).getValueType();
+    EVT NVT = Node->getValueType(0);
+
+    // FIXME: Only f32 to i64 conversions are supported.
+    if (VT != MVT::f32 || NVT != MVT::i64)
+      break;
+
+    // Expand f32 -> i64 conversion
+    // This algorithm comes from compiler-rt's implementation of fixsfdi:
+    // https://github.com/llvm-mirror/compiler-rt/blob/master/lib/builtins/fixsfdi.c
+    EVT IntVT = EVT::getIntegerVT(*DAG.getContext(),
+                                  VT.getSizeInBits());
+    SDValue ExponentMask = DAG.getConstant(0x7F800000, IntVT);
+    SDValue ExponentLoBit = DAG.getConstant(23, IntVT);
+    SDValue Bias = DAG.getConstant(127, IntVT);
+    SDValue SignMask = DAG.getConstant(APInt::getSignBit(VT.getSizeInBits()),
+                                       IntVT);
+    SDValue SignLowBit = DAG.getConstant(VT.getSizeInBits() - 1, IntVT);
+    SDValue MantissaMask = DAG.getConstant(0x007FFFFF, IntVT);
+
+    SDValue Bits = DAG.getNode(ISD::BITCAST, dl, IntVT, Node->getOperand(0));
+
+    SDValue ExponentBits = DAG.getNode(ISD::SRL, dl, IntVT,
+        DAG.getNode(ISD::AND, dl, IntVT, Bits, ExponentMask),
+        DAG.getZExtOrTrunc(ExponentLoBit, dl, TLI.getShiftAmountTy(IntVT)));
+    SDValue Exponent = DAG.getNode(ISD::SUB, dl, IntVT, ExponentBits, Bias);
+
+    SDValue Sign = DAG.getNode(ISD::SRA, dl, IntVT,
+        DAG.getNode(ISD::AND, dl, IntVT, Bits, SignMask),
+        DAG.getZExtOrTrunc(SignLowBit, dl, TLI.getShiftAmountTy(IntVT)));
+    Sign = DAG.getSExtOrTrunc(Sign, dl, NVT);
+
+    SDValue R = DAG.getNode(ISD::OR, dl, IntVT,
+        DAG.getNode(ISD::AND, dl, IntVT, Bits, MantissaMask),
+        DAG.getConstant(0x00800000, IntVT));
+
+    R = DAG.getZExtOrTrunc(R, dl, NVT);
+
+
+    R = DAG.getSelectCC(dl, Exponent, ExponentLoBit,
+       DAG.getNode(ISD::SHL, dl, NVT, R,
+                   DAG.getZExtOrTrunc(
+                      DAG.getNode(ISD::SUB, dl, IntVT, Exponent, ExponentLoBit),
+                      dl, TLI.getShiftAmountTy(IntVT))),
+       DAG.getNode(ISD::SRL, dl, NVT, R,
+                   DAG.getZExtOrTrunc(
+                      DAG.getNode(ISD::SUB, dl, IntVT, ExponentLoBit, Exponent),
+                      dl, TLI.getShiftAmountTy(IntVT))),
+       ISD::SETGT);
+
+    SDValue Ret = DAG.getNode(ISD::SUB, dl, NVT,
+        DAG.getNode(ISD::XOR, dl, NVT, R, Sign),
+        Sign);
+
+    Results.push_back(DAG.getSelectCC(dl, Exponent, DAG.getConstant(0, IntVT),
+        DAG.getConstant(0, NVT), Ret, ISD::SETLT));
+    break;
+  }
   case ISD::FP_TO_UINT: {
     SDValue True, False;
     EVT VT =  Node->getOperand(0).getValueType();
diff --git a/lib/Target/R600/AMDGPUISelLowering.cpp b/lib/Target/R600/AMDGPUISelLowering.cpp
index 7ee4ccd..50856cd 100644
--- a/lib/Target/R600/AMDGPUISelLowering.cpp
+++ b/lib/Target/R600/AMDGPUISelLowering.cpp
@@ -196,6 +196,8 @@ AMDGPUTargetLowering::AMDGPUTargetLowering(TargetMachine &TM) :
 
   setOperationAction(ISD::BR_CC, MVT::i1, Expand);
 
+  setOperationAction(ISD::FP_TO_SINT, MVT::i64, Expand);
+
   setOperationAction(ISD::FNEG, MVT::v2f32, Expand);
   setOperationAction(ISD::FNEG, MVT::v4f32, Expand);
 
diff --git a/test/CodeGen/R600/fp_to_sint_i64.ll b/test/CodeGen/R600/fp_to_sint_i64.ll
new file mode 100644
index 0000000..ec3e198
--- /dev/null
+++ b/test/CodeGen/R600/fp_to_sint_i64.ll
@@ -0,0 +1,12 @@
+; FIXME: Merge into fp_to_sint.ll when EG/NI supports 64-bit types
+; RUN: llc < %s -march=r600 -mcpu=SI -verify-machineinstrs | FileCheck --check-prefix=SI %s
+
+; SI-LABEL: @fp_to_sint_i64
+; Check that the compiler doesn't crash with a "cannot select" error
+; SI: S_ENDPGM
+define void @fp_to_sint_i64 (i64 addrspace(1)* %out, float %in) {
+entry:
+  %0 = fptosi float %in to i64
+  store i64 %0, i64 addrspace(1)* %out
+  ret void
+}
-- 
1.8.1.5