linux-kernel - [LLVM PATCH] BPF: add FRAMEADDR support

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Date:	Fri, 31 Jul 2015 10:20:13 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<ast@...mgrid.com>
CC:	<hekuang@...wei.com>, <pi3orama@....com>,
	<linux-kernel@...r.kernel.org>
Subject: [LLVM PATCH] BPF: add FRAMEADDR support

After this patch now BPF backend support __builtin_frame_address()
and __builtin_dwarf_cfa().

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 lib/Target/BPF/BPFISelLowering.cpp | 20 ++++++++++++++++++++
 lib/Target/BPF/BPFISelLowering.h   |  1 +
 2 files changed, 21 insertions(+)

diff --git a/lib/Target/BPF/BPFISelLowering.cpp b/lib/Target/BPF/BPFISelLowering.cpp
index 58498a1..f1934a2 100644
--- a/lib/Target/BPF/BPFISelLowering.cpp
+++ b/lib/Target/BPF/BPFISelLowering.cpp
@@ -169,6 +169,9 @@ BPFTargetLowering::BPFTargetLowering(const TargetMachine &TM,
   MaxStoresPerMemset = MaxStoresPerMemsetOptSize = 128;
   MaxStoresPerMemcpy = MaxStoresPerMemcpyOptSize = 128;
   MaxStoresPerMemmove = MaxStoresPerMemmoveOptSize = 128;
+
+  // support __builtin_frame_address(0)
+  setOperationAction(ISD::FRAMEADDR, MVT::i32, Custom);
 }
 
 SDValue BPFTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
@@ -179,6 +182,8 @@ SDValue BPFTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
     return LowerGlobalAddress(Op, DAG);
   case ISD::SELECT_CC:
     return LowerSELECT_CC(Op, DAG);
+  case ISD::FRAMEADDR:
+    return LowerFRAMEADDR(Op, DAG);
   default:
     llvm_unreachable("unimplemented operand");
   }
@@ -509,6 +514,21 @@ SDValue BPFTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
   return DAG.getNode(BPFISD::SELECT_CC, DL, VTs, Ops);
 }
 
+SDValue BPFTargetLowering::LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const {
+  EVT VT = Op.getValueType();
+  unsigned FrameReg = BPF::R11;
+  unsigned Depth = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
+
+  if (Depth != 0) {
+    SDLoc DL(Op);
+    MachineFunction &MF = DAG.getMachineFunction();
+    DiagnosticInfoUnsupported Err(DL, *MF.getFunction(),
+                                  "only frame 0 address can be fetched", SDValue());
+    DAG.getContext()->diagnose(Err);
+  }
+  return DAG.getRegister(FrameReg, VT);
+}
+
 const char *BPFTargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch ((BPFISD::NodeType)Opcode) {
   case BPFISD::FIRST_NUMBER:
diff --git a/lib/Target/BPF/BPFISelLowering.h b/lib/Target/BPF/BPFISelLowering.h
index ec71dca..e4bf73d 100644
--- a/lib/Target/BPF/BPFISelLowering.h
+++ b/lib/Target/BPF/BPFISelLowering.h
@@ -50,6 +50,7 @@ private:
   SDValue LowerBR_CC(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
+  SDValue LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
 
   // Lower the result values of a call, copying them out of physregs into vregs
   SDValue LowerCallResult(SDValue Chain, SDValue InFlag,
-- 
1.8.3.4

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