Thumb2 parsing and encoding for LDR(immediate).

The immediate offset of the non-writeback i8 form (encoding T4) allows
negative offsets only. The positive offset form of the encoding is the
LDRT instruction. Immediate offsets in the range [0,255] use encoding T3
instead.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139254 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 44 insertions, 0 deletions

diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index b00bb0cdae..9efdd421f0 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -732,6 +732,28 @@ public:
     int64_t Val = Mem.OffsetImm->getValue();
     return Val > -256 && Val < 256;
   }
+  bool isMemNegImm8Offset() const {
+    if (Kind != Memory || Mem.OffsetRegNum != 0)
+      return false;
+    // Immediate offset in range [-255, -1].
+    if (!Mem.OffsetImm) return true;
+    int64_t Val = Mem.OffsetImm->getValue();
+    return Val > -256 && Val < 0;
+  }
+  bool isMemUImm12Offset() const {
+    // If we have an immediate that's not a constant, treat it as a label
+    // reference needing a fixup. If it is a constant, it's something else
+    // and we reject it.
+    if (Kind == Immediate && !isa<MCConstantExpr>(getImm()))
+      return true;
+
+    if (Kind != Memory || Mem.OffsetRegNum != 0)
+      return false;
+    // Immediate offset in range [0, 4095].
+    if (!Mem.OffsetImm) return true;
+    int64_t Val = Mem.OffsetImm->getValue();
+    return (Val >= 0 && Val < 4096);
+  }
   bool isMemImm12Offset() const {
     // If we have an immediate that's not a constant, treat it as a label
     // reference needing a fixup. If it is a constant, it's something else
@@ -1077,6 +1099,28 @@ public:
     Inst.addOperand(MCOperand::CreateImm(Val));
   }
 
+  void addMemNegImm8OffsetOperands(MCInst &Inst, unsigned N) const {
+    assert(N == 2 && "Invalid number of operands!");
+    int64_t Val = Mem.OffsetImm ? Mem.OffsetImm->getValue() : 0;
+    Inst.addOperand(MCOperand::CreateReg(Mem.BaseRegNum));
+    Inst.addOperand(MCOperand::CreateImm(Val));
+  }
+
+  void addMemUImm12OffsetOperands(MCInst &Inst, unsigned N) const {
+    assert(N == 2 && "Invalid number of operands!");
+    // If this is an immediate, it's a label reference.
+    if (Kind == Immediate) {
+      addExpr(Inst, getImm());
+      Inst.addOperand(MCOperand::CreateImm(0));
+      return;
+    }
+
+    // Otherwise, it's a normal memory reg+offset.
+    int64_t Val = Mem.OffsetImm ? Mem.OffsetImm->getValue() : 0;
+    Inst.addOperand(MCOperand::CreateReg(Mem.BaseRegNum));
+    Inst.addOperand(MCOperand::CreateImm(Val));
+  }
+
   void addMemImm12OffsetOperands(MCInst &Inst, unsigned N) const {
     assert(N == 2 && "Invalid number of operands!");
     // If this is an immediate, it's a label reference.