ARM: implement support for the UDF mnemonic

The UDF instruction is a reserved undefined instruction space.  The assembler
mnemonic was introduced with ARM ARM rev C.a.  The instruction is not predicated
and the immediate constant is ignored by the CPU.  Add support for the three
encodings for this instruction.

The changes to the invalid instruction test is due to the fact that the invalid
instructions actually overlap with the undefined instruction.  Introduction of
the new instruction results in a partial decode as an undefined sequence.  Drop
the tests as they are invalid instruction patterns anyways.

llvm-svn: 208751

4 files changed, 37 insertions, 2 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 1d2a7e1be43..d449730e999 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -1967,6 +1967,18 @@ def DBG : AI<(outs), (ins imm0_15:$opt), MiscFrm, NoItinerary, "dbg", "\t$opt",
   let Inst{3-0} = opt;
 }
 
+// A8.8.247  UDF - Undefined (Encoding A1)
+def UDF : AInoP<(outs), (ins imm0_65535:$imm16), MiscFrm, NoItinerary,
+                "udf", "\t$imm16", []> {
+  bits<16> imm16;
+  let Inst{31-28} = 0b1110; // AL
+  let Inst{27-25} = 0b011;
+  let Inst{24-20} = 0b11111;
+  let Inst{19-8} = imm16{15-4};
+  let Inst{7-4} = 0b1111;
+  let Inst{3-0} = imm16{3-0};
+}
+
 /*
  * A5.4 Permanently UNDEFINED instructions.
  *
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb.td b/llvm/lib/Target/ARM/ARMInstrThumb.td
index 170c2ffab54..ff3832d98b5 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb.td
@@ -1193,6 +1193,15 @@ def tTST :                      // A8.6.230
                [(ARMcmpZ (and_su tGPR:$Rn, tGPR:$Rm), 0)]>,
                Sched<[WriteALU]>;
 
+// A8.8.247  UDF - Undefined (Encoding T1)
+def tUDF : TI<(outs), (ins imm0_255:$imm8), IIC_Br, "udf\t$imm8", []>,
+           Encoding16 {
+  bits<8> imm8;
+  let Inst{15-12} = 0b1101;
+  let Inst{11-8} = 0b1110;
+  let Inst{7-0} = imm8;
+}
+
 // Zero-extend byte
 def tUXTB :                     // A8.6.262
   T1pIMiscEncode<{0,0,1,0,1,1,?}, (outs tGPR:$Rd), (ins tGPR:$Rm),
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index 1e4aa0d6abe..28f528a510e 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -2407,6 +2407,19 @@ def t2UBFX: T2TwoRegBitFI<
   let Inst{15} = 0;
 }
 
+// A8.8.247  UDF - Undefined (Encoding T2)
+def t2UDF
+    : T2XI<(outs), (ins imm0_65535:$imm16), IIC_Br, "udf.w\t$imm16", []> {
+  bits<16> imm16;
+  let Inst{31-29} = 0b111;
+  let Inst{28-27} = 0b10;
+  let Inst{26-20} = 0b1111111;
+  let Inst{19-16} = imm16{15-12};
+  let Inst{15} = 0b1;
+  let Inst{14-12} = 0b010;
+  let Inst{11-0} = imm16{11-0};
+}
+
 // A8.6.18  BFI - Bitfield insert (Encoding T1)
 let Constraints = "$src = $Rd" in {
   def t2BFI : T2TwoRegBitFI<(outs rGPR:$Rd),
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 987f14d5dcb..d24c83abe11 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5094,8 +5094,9 @@ getMnemonicAcceptInfo(StringRef Mnemonic, StringRef FullInst,
 
   if (Mnemonic == "bkpt" || Mnemonic == "cbnz" || Mnemonic == "setend" ||
       Mnemonic == "cps" ||  Mnemonic == "it" ||  Mnemonic == "cbz" ||
-      Mnemonic == "trap" || Mnemonic == "hlt" || Mnemonic.startswith("crc32") ||
-      Mnemonic.startswith("cps") || Mnemonic.startswith("vsel") ||
+      Mnemonic == "trap" || Mnemonic == "hlt" || Mnemonic == "udf" ||
+      Mnemonic.startswith("crc32") || Mnemonic.startswith("cps") ||
+      Mnemonic.startswith("vsel") ||
       Mnemonic == "vmaxnm" || Mnemonic == "vminnm" || Mnemonic == "vcvta" ||
       Mnemonic == "vcvtn" || Mnemonic == "vcvtp" || Mnemonic == "vcvtm" ||
       Mnemonic == "vrinta" || Mnemonic == "vrintn" || Mnemonic == "vrintp" ||