[IR] Add a dedicated FNeg IR Instruction

The IEEE-754 Standard makes it clear that fneg(x) and
fsub(-0.0, x) are two different operations. The former is a bitwise
operation, while the latter is an arithmetic operation. This patch
creates a dedicated FNeg IR Instruction to model that behavior.

Differential Revision: https://reviews.llvm.org/D53877

llvm-svn: 346774

2 files changed, 98 insertions, 1 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 56e05f8f085..3b1d54f82cb 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -964,6 +964,20 @@ static int getDecodedCastOpcode(unsigned Val) {
   }
 }
 
+static int getDecodedUnaryOpcode(unsigned Val, Type *Ty) {
+  bool IsFP = Ty->isFPOrFPVectorTy();
+  // UnOps are only valid for int/fp or vector of int/fp types
+  if (!IsFP && !Ty->isIntOrIntVectorTy())
+    return -1;
+
+  switch (Val) {
+  default:
+    return -1;
+  case bitc::UNOP_NEG:
+    return IsFP ? Instruction::FNeg : -1;
+  }
+}
+
 static int getDecodedBinaryOpcode(unsigned Val, Type *Ty) {
   bool IsFP = Ty->isFPOrFPVectorTy();
   // BinOps are only valid for int/fp or vector of int/fp types
@@ -2317,6 +2331,19 @@ Error BitcodeReader::parseConstants() {
       }
       break;
     }
+    case bitc::CST_CODE_CE_UNOP: {  // CE_UNOP: [opcode, opval]
+      if (Record.size() < 2)
+        return error("Invalid record");
+      int Opc = getDecodedUnaryOpcode(Record[0], CurTy);
+      if (Opc < 0) {
+        V = UndefValue::get(CurTy);  // Unknown unop.
+      } else {
+        Constant *LHS = ValueList.getConstantFwdRef(Record[1], CurTy);
+        unsigned Flags = 0;
+        V = ConstantExpr::get(Opc, LHS, Flags);
+      }
+      break;
+    }
     case bitc::CST_CODE_CE_BINOP: {  // CE_BINOP: [opcode, opval, opval]
       if (Record.size() < 3)
         return error("Invalid record");
@@ -3535,7 +3562,27 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
       I = nullptr;
       continue;
     }
+    case bitc::FUNC_CODE_INST_UNOP: {    // UNOP: [opval, ty, opcode]
+      unsigned OpNum = 0;
+      Value *LHS;
+      if (getValueTypePair(Record, OpNum, NextValueNo, LHS) ||
+          OpNum+1 > Record.size())
+        return error("Invalid record");
 
+      int Opc = getDecodedUnaryOpcode(Record[OpNum++], LHS->getType());
+      if (Opc == -1)
+        return error("Invalid record");
+      I = UnaryOperator::Create((Instruction::UnaryOps)Opc, LHS);
+      InstructionList.push_back(I);
+      if (OpNum < Record.size()) {
+        if (isa<FPMathOperator>(I)) {
+          FastMathFlags FMF = getDecodedFastMathFlags(Record[OpNum]);
+          if (FMF.any())
+            I->setFastMathFlags(FMF);
+        }
+      }
+      break;
+    }
     case bitc::FUNC_CODE_INST_BINOP: {    // BINOP: [opval, ty, opval, opcode]
       unsigned OpNum = 0;
       Value *LHS, *RHS;
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index f4634c9d3f4..06eb0f76254 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -112,6 +112,8 @@ enum {
 
   // FUNCTION_BLOCK abbrev id's.
   FUNCTION_INST_LOAD_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
+  FUNCTION_INST_UNOP_ABBREV,
+  FUNCTION_INST_UNOP_FLAGS_ABBREV,
   FUNCTION_INST_BINOP_ABBREV,
   FUNCTION_INST_BINOP_FLAGS_ABBREV,
   FUNCTION_INST_CAST_ABBREV,
@@ -513,6 +515,13 @@ static unsigned getEncodedCastOpcode(unsigned Opcode) {
   }
 }
 
+static unsigned getEncodedUnaryOpcode(unsigned Opcode) {
+  switch (Opcode) {
+  default: llvm_unreachable("Unknown binary instruction!");
+  case Instruction::FNeg: return bitc::UNOP_NEG;
+  }
+}
+
 static unsigned getEncodedBinaryOpcode(unsigned Opcode) {
   switch (Opcode) {
   default: llvm_unreachable("Unknown binary instruction!");
@@ -2384,6 +2393,16 @@ void ModuleBitcodeWriter::writeConstants(unsigned FirstVal, unsigned LastVal,
             Record.push_back(Flags);
         }
         break;
+      case Instruction::FNeg: {
+        assert(CE->getNumOperands() == 1 && "Unknown constant expr!");
+        Code = bitc::CST_CODE_CE_UNOP;
+        Record.push_back(getEncodedUnaryOpcode(CE->getOpcode()));
+        Record.push_back(VE.getValueID(C->getOperand(0)));
+        uint64_t Flags = getOptimizationFlags(CE);
+        if (Flags != 0)
+          Record.push_back(Flags);
+        break;
+      }
       case Instruction::GetElementPtr: {
         Code = bitc::CST_CODE_CE_GEP;
         const auto *GO = cast<GEPOperator>(C);
@@ -2556,7 +2575,19 @@ void ModuleBitcodeWriter::writeInstruction(const Instruction &I,
       }
     }
     break;
-
+  case Instruction::FNeg: {
+    Code = bitc::FUNC_CODE_INST_UNOP;
+    if (!pushValueAndType(I.getOperand(0), InstID, Vals))
+      AbbrevToUse = FUNCTION_INST_UNOP_ABBREV;
+    Vals.push_back(getEncodedUnaryOpcode(I.getOpcode()));
+    uint64_t Flags = getOptimizationFlags(&I);
+    if (Flags != 0) {
+      if (AbbrevToUse == FUNCTION_INST_UNOP_ABBREV)
+        AbbrevToUse = FUNCTION_INST_UNOP_FLAGS_ABBREV;
+      Vals.push_back(Flags);
+    }
+    break;
+  }
   case Instruction::GetElementPtr: {
     Code = bitc::FUNC_CODE_INST_GEP;
     AbbrevToUse = FUNCTION_INST_GEP_ABBREV;
@@ -3217,6 +3248,25 @@ void ModuleBitcodeWriter::writeBlockInfo() {
         FUNCTION_INST_LOAD_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
+  { // INST_UNOP abbrev for FUNCTION_BLOCK.
+    auto Abbv = std::make_shared<BitCodeAbbrev>();
+    Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNOP));
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
+    if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
+        FUNCTION_INST_UNOP_ABBREV)
+      llvm_unreachable("Unexpected abbrev ordering!");
+  }
+  { // INST_UNOP_FLAGS abbrev for FUNCTION_BLOCK.
+    auto Abbv = std::make_shared<BitCodeAbbrev>();
+    Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNOP));
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8)); // flags
+    if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
+        FUNCTION_INST_UNOP_FLAGS_ABBREV)
+      llvm_unreachable("Unexpected abbrev ordering!");
+  }
   { // INST_BINOP abbrev for FUNCTION_BLOCK.
     auto Abbv = std::make_shared<BitCodeAbbrev>();
     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));