bpf: New decoder namespace for 32-bit subregister load/store

When -mattr=+alu32 passed to the disassembler, use decoder namespace for
32-bit subregister.

This is to disassemble load and store instructions in preferred B format
as described in previous commit:

      w = *(u8 *) (r + off) // BPF_LDX | BPF_B
      w = *(u16 *)(r + off) // BPF_LDX | BPF_H
      w = *(u32 *)(r + off) // BPF_LDX | BPF_W

      *(u8 *) (r + off) = w // BPF_STX | BPF_B
      *(u16 *)(r + off) = w // BPF_STX | BPF_H
      *(u32 *)(r + off) = w // BPF_STX | BPF_W

NOTE: all other instructions should still use the default decoder
      namespace.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Yonghong Song <yhs@fb.com>
llvm-svn: 325990

1 files changed, 43 insertions, 2 deletions

diff --git a/llvm/lib/Target/BPF/Disassembler/BPFDisassembler.cpp b/llvm/lib/Target/BPF/Disassembler/BPFDisassembler.cpp
index 6fc87d79c43..e7790ddb3d7 100644
--- a/llvm/lib/Target/BPF/Disassembler/BPFDisassembler.cpp
+++ b/llvm/lib/Target/BPF/Disassembler/BPFDisassembler.cpp
@@ -35,6 +35,34 @@ namespace {
 /// A disassembler class for BPF.
 class BPFDisassembler : public MCDisassembler {
 public:
+  enum BPF_CLASS {
+    BPF_LD = 0x0,
+    BPF_LDX = 0x1,
+    BPF_ST = 0x2,
+    BPF_STX = 0x3,
+    BPF_ALU = 0x4,
+    BPF_JMP = 0x5,
+    BPF_RES = 0x6,
+    BPF_ALU64 = 0x7
+  };
+
+  enum BPF_SIZE {
+    BPF_W = 0x0,
+    BPF_H = 0x1,
+    BPF_B = 0x2,
+    BPF_DW = 0x3
+  };
+
+  enum BPF_MODE {
+    BPF_IMM = 0x0,
+    BPF_ABS = 0x1,
+    BPF_IND = 0x2,
+    BPF_MEM = 0x3,
+    BPF_LEN = 0x4,
+    BPF_MSH = 0x5,
+    BPF_XADD = 0x6
+  };
+
   BPFDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
       : MCDisassembler(STI, Ctx) {}
   ~BPFDisassembler() override = default;
@@ -43,6 +71,10 @@ public:
                               ArrayRef<uint8_t> Bytes, uint64_t Address,
                               raw_ostream &VStream,
                               raw_ostream &CStream) const override;
+
+  uint8_t getInstClass(uint64_t Inst) const { return (Inst >> 56) & 0x7; };
+  uint8_t getInstSize(uint64_t Inst) const { return (Inst >> 59) & 0x3; };
+  uint8_t getInstMode(uint64_t Inst) const { return (Inst >> 61) & 0x7; };
 };
 
 } // end anonymous namespace
@@ -141,8 +173,17 @@ DecodeStatus BPFDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
   Result = readInstruction64(Bytes, Address, Size, Insn, IsLittleEndian);
   if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
 
-  Result = decodeInstruction(DecoderTableBPF64, Instr, Insn,
-                             Address, this, STI);
+  uint8_t InstClass = getInstClass(Insn);
+  if ((InstClass == BPF_LDX || InstClass == BPF_STX) &&
+      getInstSize(Insn) != BPF_DW &&
+      getInstMode(Insn) == BPF_MEM &&
+      STI.getFeatureBits()[BPF::ALU32])
+    Result = decodeInstruction(DecoderTableBPFALU3264, Instr, Insn, Address,
+                               this, STI);
+  else
+    Result = decodeInstruction(DecoderTableBPF64, Instr, Insn, Address, this,
+                               STI);
+
   if (Result == MCDisassembler::Fail) return MCDisassembler::Fail;
 
   switch (Instr.getOpcode()) {