Fix issues with the ARM bl and blx thumb instructions and the J1 and J2 bits

for the assembler and disassembler.  Which were not being set/read correctly
for offsets greater than 22 bits in some cases.

Changes to lib/Target/ARM/ARMAsmBackend.cpp from Gideon Myles!

llvm-svn: 156118

1 files changed, 34 insertions, 4 deletions

diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 28ea0d256ed..80b2b235bed 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -3339,10 +3339,25 @@ static DecodeStatus DecodePostIdxReg(MCInst &Inst, unsigned Insn,
 
 static DecodeStatus DecodeThumbBLXOffset(MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
+  // Val is passed in as S:J1:J2:imm10H:imm10L:’0’
+  // Note only one trailing zero not two.  Also the J1 and J2 values are from
+  // the encoded instruction.  So here change to I1 and I2 values via:
+  // I1 = NOT(J1 EOR S);
+  // I2 = NOT(J2 EOR S);
+  // and build the imm32 with two trailing zeros as documented:
+  // imm32 = SignExtend(S:I1:I2:imm10H:imm10L:’00’, 32);
+  unsigned S = (Val >> 23) & 1;
+  unsigned J1 = (Val >> 22) & 1;
+  unsigned J2 = (Val >> 21) & 1;
+  unsigned I1 = !(J1 ^ S);
+  unsigned I2 = !(J2 ^ S);
+  unsigned tmp = (Val & ~0x600000) | (I1 << 22) | (I2 << 21);
+  int imm32 = SignExtend32<25>(tmp << 1);
+
   if (!tryAddingSymbolicOperand(Address,
-                                (Address & ~2u) + SignExtend32<22>(Val << 1) + 4,
+                                (Address & ~2u) + imm32 + 4,
                                 true, 4, Inst, Decoder))
-    Inst.addOperand(MCOperand::CreateImm(SignExtend32<22>(Val << 1)));
+    Inst.addOperand(MCOperand::CreateImm(imm32));
   return MCDisassembler::Success;
 }
 
@@ -3456,9 +3471,24 @@ DecodeThumbBCCTargetOperand(MCInst &Inst, unsigned Val,
 
 static DecodeStatus DecodeThumbBLTargetOperand(MCInst &Inst, unsigned Val,
                                        uint64_t Address, const void *Decoder){
-  if (!tryAddingSymbolicOperand(Address, Address + SignExtend32<22>(Val<<1) + 4,
+  // Val is passed in as S:J1:J2:imm10:imm11
+  // Note no trailing zero after imm11.  Also the J1 and J2 values are from
+  // the encoded instruction.  So here change to I1 and I2 values via:
+  // I1 = NOT(J1 EOR S);
+  // I2 = NOT(J2 EOR S);
+  // and build the imm32 with one trailing zero as documented:
+  // imm32 = SignExtend(S:I1:I2:imm10:imm11:’0’, 32);
+  unsigned S = (Val >> 23) & 1;
+  unsigned J1 = (Val >> 22) & 1;
+  unsigned J2 = (Val >> 21) & 1;
+  unsigned I1 = !(J1 ^ S);
+  unsigned I2 = !(J2 ^ S);
+  unsigned tmp = (Val & ~0x600000) | (I1 << 22) | (I2 << 21);
+  int imm32 = SignExtend32<25>(tmp << 1);
+
+  if (!tryAddingSymbolicOperand(Address, Address + imm32 + 4,
                                 true, 4, Inst, Decoder))
-    Inst.addOperand(MCOperand::CreateImm(SignExtend32<22>(Val << 1)));
+    Inst.addOperand(MCOperand::CreateImm(imm32));
   return MCDisassembler::Success;
 }