This adds range checking for "ldr Rn, [pc, #imm]" Thumb

instructions. With this patch:

1. ldr.n is recognized as mnemonic for the short encoding
2. ldr.w is recognized as menmonic for the long encoding
3. ldr will map to either short or long encodings depending on the size of the offset

llvm-svn: 186831

4 files changed, 62 insertions, 25 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrThumb.td b/llvm/lib/Target/ARM/ARMInstrThumb.td
index a0edaba04e8..e7218c66586 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb.td
@@ -100,6 +100,13 @@ class OperandUnsignedOffset_b8s2 : AsmOperandClass {
 
 def UnsignedOffset_b8s2 : OperandUnsignedOffset_b8s2;
 
+// thumb style PC relative operand. signed, 8 bits magnitude,
+// two bits shift. can be represented as either [pc, #imm], #imm,
+// or relocatable expression...
+def ThumbMemPC : AsmOperandClass {
+  let Name = "ThumbMemPC";
+}
+
 let OperandType = "OPERAND_PCREL" in {
 def t_brtarget : Operand<OtherVT> {
   let EncoderMethod = "getThumbBRTargetOpValue";
@@ -132,6 +139,15 @@ def t_blxtarget : Operand<i32> {
   let EncoderMethod = "getThumbBLXTargetOpValue";
   let DecoderMethod = "DecodeThumbBLXOffset";
 }
+
+// t_addrmode_pc := <label> => pc + imm8 * 4
+//
+def t_addrmode_pc : Operand<i32> {
+  let EncoderMethod = "getAddrModePCOpValue";
+  let DecoderMethod = "DecodeThumbAddrModePC";
+  let PrintMethod = "printThumbLdrLabelOperand";
+  let ParserMatchClass = ThumbMemPC;
+}
 }
 
 // t_addrmode_rr := reg + reg
@@ -228,14 +244,6 @@ def t_addrmode_sp : Operand<i32>,
   let MIOperandInfo = (ops GPR:$base, i32imm:$offsimm);
 }
 
-// t_addrmode_pc := <label> => pc + imm8 * 4
-//
-def t_addrmode_pc : Operand<i32> {
-  let EncoderMethod = "getAddrModePCOpValue";
-  let DecoderMethod = "DecodeThumbAddrModePC";
-  let PrintMethod = "printThumbLdrLabelOperand";
-}
-
 //===----------------------------------------------------------------------===//
 //  Miscellaneous Instructions.
 //
@@ -640,11 +648,9 @@ def tLDRspi : T1pIs<(outs tGPR:$Rt), (ins t_addrmode_sp:$addr), IIC_iLoad_i,
   let Inst{7-0} = addr;
 }
 
-// Load tconstpool
-// FIXME: Use ldr.n to work around a darwin assembler bug.
-let canFoldAsLoad = 1, isReMaterializable = 1, isCodeGenOnly = 1 in
+let canFoldAsLoad = 1, isReMaterializable = 1 in
 def tLDRpci : T1pIs<(outs tGPR:$Rt), (ins t_addrmode_pc:$addr), IIC_iLoad_i,
-                  "ldr", ".n\t$Rt, $addr",
+                  "ldr", "\t$Rt, $addr",
                   [(set tGPR:$Rt, (load (ARMWrapper tconstpool:$addr)))]>,
               T1Encoding<{0,1,0,0,1,?}> {
   // A6.2 & A8.6.59
@@ -654,17 +660,8 @@ def tLDRpci : T1pIs<(outs tGPR:$Rt), (ins t_addrmode_pc:$addr), IIC_iLoad_i,
   let Inst{7-0}  = addr;
 }
 
-// FIXME: Remove this entry when the above ldr.n workaround is fixed.
-// For assembly/disassembly use only.
-def tLDRpciASM : T1pIs<(outs tGPR:$Rt), (ins t_addrmode_pc:$addr), IIC_iLoad_i,
-                       "ldr", "\t$Rt, $addr", []>,
-                 T1Encoding<{0,1,0,0,1,?}> {
-  // A6.2 & A8.6.59
-  bits<3> Rt;
-  bits<8> addr;
-  let Inst{10-8} = Rt;
-  let Inst{7-0}  = addr;
-}
+def : tInstAlias<"ldr${p}.n $Rt, $addr", 
+                 (tLDRpci tGPR:$Rt, t_addrmode_pc:$addr, pred:$p), 0>;
 
 // A8.6.194 & A8.6.192
 defm tSTR  : thumb_st_rr_ri_enc<0b000, 0b0110, t_addrmode_rrs4,
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index 5a425c69228..8e5e8c1735a 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -4399,7 +4399,7 @@ def t2LDRSHpcrel  : t2AsmPseudo<"ldrsh${p} $Rt, $addr",
                          (ins GPRnopc:$Rt, t2ldr_pcrel_imm12:$addr, pred:$p)>;
     // Version w/ the .w suffix.
 def : t2InstAlias<"ldr${p}.w $Rt, $addr",
-                  (t2LDRpcrel GPRnopc:$Rt, t2ldr_pcrel_imm12:$addr, pred:$p)>;
+                  (t2LDRpcrel GPRnopc:$Rt, t2ldr_pcrel_imm12:$addr, pred:$p), 0>;
 def : t2InstAlias<"ldrb${p}.w $Rt, $addr",
                   (t2LDRBpcrel GPRnopc:$Rt, t2ldr_pcrel_imm12:$addr, pred:$p)>;
 def : t2InstAlias<"ldrh${p}.w $Rt, $addr",
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index fc1faffd0bb..6d885a0d918 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -609,6 +609,26 @@ public:
     }
     return false;
   }
+  // checks whether this operand is a memory operand computed as an offset
+  // applied to PC. the offset may have 8 bits of magnitude and is represented
+  // with two bits of shift. textually it may be either [pc, #imm], #imm or 
+  // relocable expression...
+  bool isThumbMemPC() const {
+    int64_t Val = 0;
+    if (isImm()) {
+      if (isa<MCSymbolRefExpr>(Imm.Val)) return true;
+      const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(Imm.Val);
+      if (!CE) return false;
+      Val = CE->getValue();
+    }
+    else if (isMem()) {
+      if(!Memory.OffsetImm || Memory.OffsetRegNum) return false;
+      if(Memory.BaseRegNum != ARM::PC) return false;
+      Val = Memory.OffsetImm->getValue();
+    }
+    else return false;
+    return ((Val % 4) == 0) && (Val >= -1020) && (Val <= 1020);
+  }
   bool isFPImm() const {
     if (!isImm()) return false;
     const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
@@ -1698,6 +1718,26 @@ public:
     Inst.addOperand(MCOperand::CreateExpr(SR));
   }
 
+  void addThumbMemPCOperands(MCInst &Inst, unsigned N) const {
+    assert(N == 1 && "Invalid number of operands!");
+    if (isImm()) {
+      const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
+      if (CE) {
+        Inst.addOperand(MCOperand::CreateImm(CE->getValue()));
+        return;
+      }
+
+      const MCSymbolRefExpr *SR = dyn_cast<MCSymbolRefExpr>(Imm.Val);
+      assert(SR && "Unknown value type!");
+      Inst.addOperand(MCOperand::CreateExpr(SR));
+      return;
+    }
+
+    assert(isMem()  && "Unknown value type!");
+    assert(isa<MCConstantExpr>(Memory.OffsetImm) && "Unknown value type!");
+    Inst.addOperand(MCOperand::CreateImm(Memory.OffsetImm->getValue()));
+  }
+
   void addARMSOImmNotOperands(MCInst &Inst, unsigned N) const {
     assert(N == 1 && "Invalid number of operands!");
     // The operand is actually a so_imm, but we have its bitwise
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
index 8baa3a6ce6a..b1e25d8b89e 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
@@ -152,7 +152,7 @@ static unsigned getRelaxedOpcode(unsigned Op) {
   switch (Op) {
   default: return Op;
   case ARM::tBcc:       return ARM::t2Bcc;
-  case ARM::tLDRpciASM: return ARM::t2LDRpci;
+  case ARM::tLDRpci:    return ARM::t2LDRpci;
   case ARM::tADR:       return ARM::t2ADR;
   case ARM::tB:         return ARM::t2B;
   }