ARM thumb assembly parsing for arithmetic flag setting instructions.

Thumb one requires that many arithmetic instruction forms have an 'S'
suffix. For Thumb2, the whether the suffix is required or precluded depends
on whether the instruction is in an IT block. Use target parser predicates
to check for these sorts of context-sensitive constraints.

llvm-svn: 137746

3 files changed, 62 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrFormats.td b/llvm/lib/Target/ARM/ARMInstrFormats.td
index ba378ed5fed..fecc6bfdef8 100644
--- a/llvm/lib/Target/ARM/ARMInstrFormats.td
+++ b/llvm/lib/Target/ARM/ARMInstrFormats.td
@@ -236,6 +236,10 @@ class InstTemplate<AddrMode am, int sz, IndexMode im,
   Domain D = d;
   bit isUnaryDataProc = 0;
   bit canXformTo16Bit = 0;
+  // The instruction is a 16-bit flag setting Thumb instruction. Used
+  // by the parser to determine whether to require the 'S' suffix on the
+  // mnemonic (when not in an IT block) or preclude it (when in an IT block).
+  bit thumbArithFlagSetting = 0;
 
   // If this is a pseudo instruction, mark it isCodeGenOnly.
   let isCodeGenOnly = !eq(!cast<string>(f), "Pseudo");
@@ -247,6 +251,7 @@ class InstTemplate<AddrMode am, int sz, IndexMode im,
   let TSFlags{13}    = isUnaryDataProc;
   let TSFlags{14}    = canXformTo16Bit;
   let TSFlags{17-15} = D.Value;
+  let TSFlags{18}    = thumbArithFlagSetting;
 
   let Constraints = cstr;
   let Itinerary = itin;
@@ -895,6 +900,7 @@ class Thumb1sI<dag oops, dag iops, AddrMode am, int sz,
   let InOperandList = !con(iops, (ins pred:$p));
   let AsmString = !strconcat(opc, "${s}${p}", asm);
   let Pattern = pattern;
+  let thumbArithFlagSetting = 1;
   list<Predicate> Predicates = [IsThumb, IsThumb1Only];
 }
 
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 1f298b3759c..afc1e251c0d 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -78,6 +78,9 @@ class ARMAsmParser : public MCTargetAsmParser {
   bool isThumbOne() const {
     return isThumb() && (STI.getFeatureBits() & ARM::FeatureThumb2) == 0;
   }
+  bool isThumbTwo() const {
+    return isThumb() && (STI.getFeatureBits() & ARM::FeatureThumb2);
+  }
   void SwitchMode() {
     unsigned FB = ComputeAvailableFeatures(STI.ToggleFeature(ARM::ModeThumb));
     setAvailableFeatures(FB);
@@ -146,6 +149,10 @@ class ARMAsmParser : public MCTargetAsmParser {
                           const SmallVectorImpl<MCParsedAsmOperand*> &Ops);
 
 public:
+  enum ARMMatchResultTy {
+    Match_RequiresITBlock = FIRST_TARGET_MATCH_RESULT_TY
+  };
+
   ARMAsmParser(MCSubtargetInfo &_STI, MCAsmParser &_Parser)
     : MCTargetAsmParser(), STI(_STI), Parser(_Parser) {
     MCAsmParserExtension::Initialize(_Parser);
@@ -160,6 +167,8 @@ public:
                         SmallVectorImpl<MCParsedAsmOperand*> &Operands);
   bool ParseDirective(AsmToken DirectiveID);
 
+  unsigned checkTargetMatchPredicate(MCInst &Inst);
+
   bool MatchAndEmitInstruction(SMLoc IDLoc,
                                SmallVectorImpl<MCParsedAsmOperand*> &Operands,
                                MCStreamer &Out);
@@ -2975,6 +2984,44 @@ processInstruction(MCInst &Inst,
   }
 }
 
+// FIXME: We would really prefer to have MCInstrInfo (the wrapper around
+// the ARMInsts array) instead. Getting that here requires awkward
+// API changes, though. Better way?
+namespace llvm {
+extern MCInstrDesc ARMInsts[];
+}
+static MCInstrDesc &getInstDesc(unsigned Opcode) {
+  return ARMInsts[Opcode];
+}
+
+unsigned ARMAsmParser::checkTargetMatchPredicate(MCInst &Inst) {
+  // 16-bit thumb arithmetic instructions either require or preclude the 'S'
+  // suffix depending on whether they're in an IT block or not.
+  MCInstrDesc &MCID = getInstDesc(Inst.getOpcode());
+  if (MCID.TSFlags & ARMII::ThumbArithFlagSetting) {
+    assert(MCID.hasOptionalDef() &&
+           "optionally flag setting instruction missing optional def operand");
+    assert(MCID.NumOperands == Inst.getNumOperands() &&
+           "operand count mismatch!");
+    // Find the optional-def operand (cc_out).
+    unsigned OpNo;
+    for (OpNo = 0;
+         !MCID.OpInfo[OpNo].isOptionalDef() && OpNo < MCID.NumOperands;
+         ++OpNo)
+      ;
+    // If we're parsing Thumb1, reject it completely.
+    if (isThumbOne() && Inst.getOperand(OpNo).getReg() != ARM::CPSR)
+      return Match_MnemonicFail;
+    // If we're parsing Thumb2, which form is legal depends on whether we're
+    // in an IT block.
+    // FIXME: We don't yet do IT blocks, so just always consider it to be
+    // that we aren't in one until we do.
+    if (isThumbTwo() && Inst.getOperand(OpNo).getReg() != ARM::CPSR)
+      return Match_RequiresITBlock;
+  }
+  return Match_Success;
+}
+
 bool ARMAsmParser::
 MatchAndEmitInstruction(SMLoc IDLoc,
                         SmallVectorImpl<MCParsedAsmOperand*> &Operands,
@@ -3013,9 +3060,11 @@ MatchAndEmitInstruction(SMLoc IDLoc,
     return Error(ErrorLoc, "invalid operand for instruction");
   }
   case Match_MnemonicFail:
-    return Error(IDLoc, "unrecognized instruction mnemonic");
+    return Error(IDLoc, "invalid instruction");
   case Match_ConversionFail:
     return Error(IDLoc, "unable to convert operands to instruction");
+  case Match_RequiresITBlock:
+    return Error(IDLoc, "instruction only valid inside IT block");
   }
 
   llvm_unreachable("Implement any new match types added!");
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h
index 5fede1588b4..0a8fb6a03b6 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h
@@ -384,6 +384,12 @@ namespace ARMII {
     // a 16-bit Thumb instruction if certain conditions are met.
     Xform16Bit    = 1 << 14,
 
+    // ThumbArithFlagSetting - The instruction is a 16-bit flag setting Thumb
+    // instruction. Used by the parser to determine whether to require the 'S'
+    // suffix on the mnemonic (when not in an IT block) or preclude it (when
+    // in an IT block).
+    ThumbArithFlagSetting = 1 << 18,
+
     //===------------------------------------------------------------------===//
     // Code domain.
     DomainShift   = 15,