From 84a28d4e76553e124af965888b01d4874e8d821e Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 30 Oct 2006 08:00:44 +0000
Subject: Lower jumptable to BR_JT. The legalizer can lower it to a BRIND or
 let the target custom lower it.

llvm-svn: 31293
---
 llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp | 48 +++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

(limited to 'llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp')

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 125e46c0cad..bb4280b5c80 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -16,6 +16,7 @@
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/CallingConv.h"
 #include "llvm/Constants.h"
@@ -1240,6 +1241,53 @@ SDOperand SelectionDAGLegalize::LegalizeOp(SDOperand Op) {
     }
     Result = DAG.UpdateNodeOperands(Result, Tmp1, Tmp2);
     break;
+  case ISD::BR_JT:
+    Tmp1 = LegalizeOp(Node->getOperand(0));  // Legalize the chain.
+    // Ensure that libcalls are emitted before a branch.
+    Tmp1 = DAG.getNode(ISD::TokenFactor, MVT::Other, Tmp1, LastCALLSEQ_END);
+    Tmp1 = LegalizeOp(Tmp1);
+    LastCALLSEQ_END = DAG.getEntryNode();
+
+    Tmp2 = LegalizeOp(Node->getOperand(1));  // Legalize the jumptable node.
+    Result = DAG.UpdateNodeOperands(Result, Tmp1, Tmp2, Node->getOperand(2));
+
+    switch (TLI.getOperationAction(ISD::BR_JT, MVT::Other)) {  
+    default: assert(0 && "This action is not supported yet!");
+    case TargetLowering::Legal: break;
+    case TargetLowering::Custom:
+      Tmp1 = TLI.LowerOperation(Result, DAG);
+      if (Tmp1.Val) Result = Tmp1;
+      break;
+    case TargetLowering::Expand: {
+      SDOperand Chain = Result.getOperand(0);
+      SDOperand Table = Result.getOperand(1);
+      SDOperand Index = Result.getOperand(2);
+
+      MVT::ValueType PTy = TLI.getPointerTy();
+      bool isPIC = TLI.getTargetMachine().getRelocationModel() == Reloc::PIC_;
+      // PIC jump table entries are 32-bit values.
+      unsigned EntrySize = isPIC ? 4 : MVT::getSizeInBits(PTy)/8;
+      Index= DAG.getNode(ISD::MUL, PTy, Index, DAG.getConstant(EntrySize, PTy));
+      SDOperand Addr = DAG.getNode(ISD::ADD, PTy, Index, Table);
+      SDOperand LD = DAG.getLoad(isPIC ? MVT::i32 : PTy, Chain, Addr, NULL, 0);
+      if (isPIC) {
+        // For PIC, the sequence is:
+        // BRIND(load(Jumptable + index) + RelocBase)
+        // RelocBase is the JumpTable on PPC and X86, GOT on Alpha
+        SDOperand Reloc;
+        if (TLI.usesGlobalOffsetTable())
+          Reloc = DAG.getNode(ISD::GLOBAL_OFFSET_TABLE, PTy);
+        else
+          Reloc = Table;
+        Addr= (PTy != MVT::i32) ? DAG.getNode(ISD::SIGN_EXTEND, PTy, LD) : Addr;
+        Addr = DAG.getNode(ISD::ADD, PTy, Addr, Reloc);
+        Result = DAG.getNode(ISD::BRIND, MVT::Other, LD.getValue(1), Addr);
+      } else {
+        Result = DAG.getNode(ISD::BRIND, MVT::Other, LD.getValue(1), LD);
+      }
+    }
+    }
+    break;
   case ISD::BRCOND:
     Tmp1 = LegalizeOp(Node->getOperand(0));  // Legalize the chain.
     // Ensure that libcalls are emitted before a return.
-- 
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