Revert [tblgen][disasm] Allow multiple encodings to disassemble to the same instruction

This reverts r363744 (git commit 9b22521)

This breaks many buildbots, e.g. http://lab.llvm.org:8011/builders/clang-atom-d525-fedora-rel/builds/203/steps/build%20stage%201/logs/stdio

llvm-svn: 363747

Author: rupprecht

llvm/include/llvm/Target/Target.td

@@ -398,49 +398,11 @@ include "llvm/Target/TargetSchedule.td"
 
 class Predicate; // Forward def
 
-class InstructionEncoding {
-  // Size of encoded instruction.
-  int Size;
-
-  // The "namespace" in which this instruction exists, on targets like ARM
-  // which multiple ISA namespaces exist.
-  string DecoderNamespace = "";
-
-  // List of predicates which will be turned into isel matching code.
-  list<Predicate> Predicates = [];
-
-  string DecoderMethod = "";
-
-  // Is the instruction decoder method able to completely determine if the
-  // given instruction is valid or not. If the TableGen definition of the
-  // instruction specifies bitpattern A??B where A and B are static bits, the
-  // hasCompleteDecoder flag says whether the decoder method fully handles the
-  // ?? space, i.e. if it is a final arbiter for the instruction validity.
-  // If not then the decoder attempts to continue decoding when the decoder
-  // method fails.
-  //
-  // This allows to handle situations where the encoding is not fully
-  // orthogonal. Example:
-  // * InstA with bitpattern 0b0000????,
-  // * InstB with bitpattern 0b000000?? but the associated decoder method
-  //   DecodeInstB() returns Fail when ?? is 0b00 or 0b11.
-  //
-  // The decoder tries to decode a bitpattern that matches both InstA and
-  // InstB bitpatterns first as InstB (because it is the most specific
-  // encoding). In the default case (hasCompleteDecoder = 1), when
-  // DecodeInstB() returns Fail the bitpattern gets rejected. By setting
-  // hasCompleteDecoder = 0 in InstB, the decoder is informed that
-  // DecodeInstB() is not able to determine if all possible values of ?? are
-  // valid or not. If DecodeInstB() returns Fail the decoder will attempt to
-  // decode the bitpattern as InstA too.
-  bit hasCompleteDecoder = 1;
-}
-
 //===----------------------------------------------------------------------===//
 // Instruction set description - These classes correspond to the C++ classes in
 // the Target/TargetInstrInfo.h file.
 //
-class Instruction : InstructionEncoding {
+class Instruction {
   string Namespace = "";
 
   dag OutOperandList;       // An dag containing the MI def operand list.
@@ -465,6 +427,10 @@ class Instruction : InstructionEncoding {
   // from the opcode.
   int Size = 0;
 
+  // DecoderNamespace - The "namespace" in which this instruction exists, on
+  // targets like ARM which multiple ISA namespaces exist.
+  string DecoderNamespace = "";
+
   // Code size, for instruction selection.
   // FIXME: What does this actually mean?
   int CodeSize = 0;
@@ -566,6 +532,31 @@ class Instruction : InstructionEncoding {
   string DisableEncoding = "";
 
   string PostEncoderMethod = "";
+  string DecoderMethod = "";
+
+  // Is the instruction decoder method able to completely determine if the
+  // given instruction is valid or not. If the TableGen definition of the
+  // instruction specifies bitpattern A??B where A and B are static bits, the
+  // hasCompleteDecoder flag says whether the decoder method fully handles the
+  // ?? space, i.e. if it is a final arbiter for the instruction validity.
+  // If not then the decoder attempts to continue decoding when the decoder
+  // method fails.
+  //
+  // This allows to handle situations where the encoding is not fully
+  // orthogonal. Example:
+  // * InstA with bitpattern 0b0000????,
+  // * InstB with bitpattern 0b000000?? but the associated decoder method
+  //   DecodeInstB() returns Fail when ?? is 0b00 or 0b11.
+  //
+  // The decoder tries to decode a bitpattern that matches both InstA and
+  // InstB bitpatterns first as InstB (because it is the most specific
+  // encoding). In the default case (hasCompleteDecoder = 1), when
+  // DecodeInstB() returns Fail the bitpattern gets rejected. By setting
+  // hasCompleteDecoder = 0 in InstB, the decoder is informed that
+  // DecodeInstB() is not able to determine if all possible values of ?? are
+  // valid or not. If DecodeInstB() returns Fail the decoder will attempt to
+  // decode the bitpattern as InstA too.
+  bit hasCompleteDecoder = 1;
 
   /// Target-specific flags. This becomes the TSFlags field in TargetInstrDesc.
   bits<64> TSFlags = 0;
@@ -602,13 +593,6 @@ class Instruction : InstructionEncoding {
   bit FastISelShouldIgnore = 0;
 }
 
-/// Defines an additional encoding that disassembles to the given instruction
-/// Like Instruction, the Inst and SoftFail fields are omitted to allow targets
-// to specify their size.
-class AdditionalEncoding<Instruction I> : InstructionEncoding {
-  Instruction AliasOf = I;
-}
-
 /// PseudoInstExpansion - Expansion information for a pseudo-instruction.
 /// Which instruction it expands to and how the operands map from the
 /// pseudo.