Add asm parsing support w/ testcases for strex/ldrex family of instructions

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128236 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index bd5546d..755b9af 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -350,6 +350,23 @@
     int64_t Value = CE->getValue();
     return ((Value & 0x3) == 0 && Value <= 1020 && Value >= -1020);
   }
+  bool isMemMode7() const {
+    if (!isMemory() ||
+        getMemPreindexed() ||
+        getMemPostindexed() ||
+        getMemOffsetIsReg() ||
+        getMemNegative() ||
+        getMemWriteback())
+      return false;
+
+    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getMemOffset());
+    if (!CE) return false;
+
+    if (CE->getValue())
+      return false;
+
+    return true;
+  }
   bool isMemModeRegThumb() const {
     if (!isMemory() || !getMemOffsetIsReg() || getMemWriteback())
       return false;
@@ -438,6 +455,15 @@
     Inst.addOperand(MCOperand::CreateImm(unsigned(getMemBarrierOpt())));
   }
 
+  void addMemMode7Operands(MCInst &Inst, unsigned N) const {
+    assert(N == 1 && isMemMode7() && "Invalid number of operands!");
+    Inst.addOperand(MCOperand::CreateReg(getMemBaseRegNum()));
+
+    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getMemOffset());
+    assert((CE || CE->getValue() == 0) &&
+           "No offset operand support in mode 7");
+  }
+
   void addMemMode5Operands(MCInst &Inst, unsigned N) const {
     assert(N == 2 && isMemMode5() && "Invalid number of operands!");