ARM: Fix encoding of hint instruction for Thumb.

"hint" space for Thumb actually overlaps the encoding space of the CPS
instruction. In actuality, hints can be defined as CPS instructions where imod
and M bits are all nil.

Handle decoding of permitted nop-compatible hints (i.e. nop, yield, wfi, wfe,
sev) in DecodeT2CPSInstruction.

This commit adds a proper diagnostic message for Imm0_4 and updates all tests.

Patch by Mihail Popa <Mihail.Popa@arm.com>.

llvm-svn: 180617

4 files changed, 22 insertions, 16 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 8aa608bc97a..5d5380f34c9 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -582,7 +582,11 @@ def Imm0_3AsmOperand: ImmAsmOperand { let Name = "Imm0_3"; }
 def imm0_3 : Operand<i32> { let ParserMatchClass = Imm0_3AsmOperand; }
 
 /// imm0_4 predicate - Immediate in the range [0,4].
-def Imm0_4AsmOperand : ImmAsmOperand { let Name = "Imm0_4"; }
+def Imm0_4AsmOperand : ImmAsmOperand
+{ 
+  let Name = "Imm0_4"; 
+  let DiagnosticType = "ImmRange0_4";  
+}
 def imm0_4 : Operand<i32>, ImmLeaf<i32, [{ return Imm >= 0 && Imm < 5; }]> {
   let ParserMatchClass = Imm0_4AsmOperand;
   let DecoderMethod = "DecodeImm0_4";
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index ad57de54c13..4dacb86df4c 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -3401,12 +3401,7 @@ class t2CPS<dag iops, string asm_op> : T2XI<(outs), iops, NoItinerary,
   bits<5> mode;
   bit M;
 
-  let Inst{31-27} = 0b11110;
-  let Inst{26}    = 0;
-  let Inst{25-20} = 0b111010;
-  let Inst{19-16} = 0b1111;
-  let Inst{15-14} = 0b10;
-  let Inst{12}    = 0;
+  let Inst{31-11} = 0b111100111010111110000;
   let Inst{10-9}  = imod;
   let Inst{8}     = M;
   let Inst{7-5}   = iflags;
@@ -3425,13 +3420,13 @@ let imod = 0, iflags = 0, M = 1 in
 
 // A6.3.4 Branches and miscellaneous control
 // Table A6-14 Change Processor State, and hint instructions
-def t2HINT : T2I<(outs), (ins imm0_255:$imm), NoItinerary, "hint", "\t$imm",[]>{
-  bits<8> imm;
-  let Inst{31-8} = 0b111100111010111110000000;
-  let Inst{7-0} = imm;
+def t2HINT : T2I<(outs), (ins imm0_4:$imm), NoItinerary, "hint", "\t$imm",[]> {
+  bits<3> imm;
+  let Inst{31-3} = 0b11110011101011111000000000000;
+  let Inst{2-0} = imm;
 }
 
-def : t2InstAlias<"hint$p.w $imm", (t2HINT imm0_255:$imm, pred:$p)>;
+def : t2InstAlias<"hint$p.w $imm", (t2HINT imm0_4:$imm, pred:$p)>;
 def : t2InstAlias<"nop$p.w", (t2HINT 0, pred:$p)>;
 def : t2InstAlias<"yield$p.w", (t2HINT 1, pred:$p)>;
 def : t2InstAlias<"wfe$p.w", (t2HINT 2, pred:$p)>;
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 20468af9a27..114cc9e5c05 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -7622,6 +7622,11 @@ MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
     return Error(IDLoc, "instruction variant requires ARMv6 or later");
   case Match_RequiresThumb2:
     return Error(IDLoc, "instruction variant requires Thumb2");
+  case Match_ImmRange0_4: {
+    SMLoc ErrorLoc = ((ARMOperand*)Operands[ErrorInfo])->getStartLoc();
+    if (ErrorLoc == SMLoc()) ErrorLoc = IDLoc;
+    return Error(ErrorLoc, "immediate operand must be in the range [0,4]");
+  }
   case Match_ImmRange0_15: {
     SMLoc ErrorLoc = ((ARMOperand*)Operands[ErrorInfo])->getStartLoc();
     if (ErrorLoc == SMLoc()) ErrorLoc = IDLoc;
diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 32b47fba514..ac937f35345 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -1953,10 +1953,12 @@ static DecodeStatus DecodeT2CPSInstruction(MCInst &Inst, unsigned Insn,
     Inst.addOperand(MCOperand::CreateImm(mode));
     if (iflags) S = MCDisassembler::SoftFail;
   } else {
-    // imod == '00' && M == '0' --> UNPREDICTABLE
-    Inst.setOpcode(ARM::t2CPS1p);
-    Inst.addOperand(MCOperand::CreateImm(mode));
-    S = MCDisassembler::SoftFail;
+    // imod == '00' && M == '0' --> this is a HINT instruction
+    int imm = fieldFromInstruction(Insn, 0, 8);
+    // HINT are defined only for immediate in [0..4]
+    if(imm > 4) return MCDisassembler::Fail;
+    Inst.setOpcode(ARM::t2HINT);
+    Inst.addOperand(MCOperand::CreateImm(imm));
   }
 
   return S;