[mlir][LLVMIR] Add support for translating FCmp & more FP constants

[myhsu]

Summary

This patch add supports for translating FCmp and more kinds of FP constants in addition to 32 & 64-bit ones. However, we can't express ppc_fp128 constants right now because the semantics for its underlying APFloat is S_PPCDoubleDouble but mlir::FloatType doesn't support such semantics.

mlir/lib/Target/LLVMIR/ConvertFromLLVMIR.cpp

Attribute Importer::getConstantAsAttr(llvm::Constant *value) {
   if (auto *ci = dyn_cast<llvm::ConstantInt>(value))
     return b.getIntegerAttr(
         IntegerType::get(context, ci->getType()->getBitWidth()),
         ci->getValue());
   if (auto *c = dyn_cast<llvm::ConstantDataArray>(value))
     if (c->isString())
       return b.getStringAttr(c->getAsString());
   if (auto *c = dyn_cast<llvm::ConstantFP>(value)) {
-    if (c->getType()->isDoubleTy())
-      return b.getFloatAttr(FloatType::getF64(context), c->getValueAPF());
-    if (c->getType()->isFloatingPointTy())
-      return b.getFloatAttr(FloatType::getF32(context), c->getValueAPF());
+    auto *type = c->getType();
+    FloatType floatTy;
+    if (type->isBFloatTy())
+      floatTy = FloatType::getBF16(context);
+    else
+      floatTy = getDLFloatType(*context, type->getScalarSizeInBits());
+    assert(floatTy && "unsupported floating point type");
+    return b.getFloatAttr(floatTy, c->getValueAPF());
   }
   if (auto *f = dyn_cast<llvm::Function>(value))
     return SymbolRefAttr::get(b.getContext(), f->getName());
 
   // Convert constant data to a dense elements attribute.
   if (auto *cd = dyn_cast<llvm::ConstantDataSequential>(value)) {
     Type type = processType(cd->getElementType());
     if (!type)
static const DenseMap<unsigned, StringRef> opcMap = {
       INST(Trunc, Trunc), INST(ZExt, ZExt), INST(SExt, SExt),
       INST(FPToUI, FPToUI), INST(FPToSI, FPToSI), INST(UIToFP, UIToFP),
       INST(SIToFP, SIToFP), INST(FPTrunc, FPTrunc), INST(FPExt, FPExt),
       INST(PtrToInt, PtrToInt), INST(IntToPtr, IntToPtr),
       INST(BitCast, Bitcast), INST(AddrSpaceCast, AddrSpaceCast),
       // FIXME: cleanuppad
       // FIXME: catchpad
       // ICmp is handled specially.
-      // FIXME: fcmp
+      // FCmp is handled specially.
       // PHI is handled specially.
       INST(Freeze, Freeze), INST(Call, Call),
       // FIXME: select
       // FIXME: vaarg
       // FIXME: extractelement
       // FIXME: insertelement
       // FIXME: shufflevector
       // FIXME: extractvalue
case llvm::CmpInst::Predicate::ICMP_ULT:
     return LLVM::ICmpPredicate::ult;
   case llvm::CmpInst::Predicate::ICMP_ULE:
     return LLVM::ICmpPredicate::ule;
   case llvm::CmpInst::Predicate::ICMP_UGT:
     return LLVM::ICmpPredicate::ugt;
   case llvm::CmpInst::Predicate::ICMP_UGE:
     return LLVM::ICmpPredicate::uge;
   }
+  llvm_unreachable("incorrect integer comparison predicate");
+}
+
+static FCmpPredicate getFCmpPredicate(llvm::CmpInst::Predicate p) {
+  switch (p) {
+  default:
     llvm_unreachable("incorrect comparison predicate");
+  case llvm::CmpInst::Predicate::FCMP_FALSE:
+    return LLVM::FCmpPredicate::_false;
+  case llvm::CmpInst::Predicate::FCMP_TRUE:
+    return LLVM::FCmpPredicate::_true;
+  case llvm::CmpInst::Predicate::FCMP_OEQ:
+    return LLVM::FCmpPredicate::oeq;
+  case llvm::CmpInst::Predicate::FCMP_ONE:
+    return LLVM::FCmpPredicate::one;
+  case llvm::CmpInst::Predicate::FCMP_OLT:
+    return LLVM::FCmpPredicate::olt;
+  case llvm::CmpInst::Predicate::FCMP_OLE:
+    return LLVM::FCmpPredicate::ole;
+  case llvm::CmpInst::Predicate::FCMP_OGT:
+    return LLVM::FCmpPredicate::ogt;
+  case llvm::CmpInst::Predicate::FCMP_OGE:
+    return LLVM::FCmpPredicate::oge;
+  case llvm::CmpInst::Predicate::FCMP_ORD:
+    return LLVM::FCmpPredicate::ord;
+  case llvm::CmpInst::Predicate::FCMP_ULT:
+    return LLVM::FCmpPredicate::ult;
+  case llvm::CmpInst::Predicate::FCMP_ULE:
+    return LLVM::FCmpPredicate::ule;
+  case llvm::CmpInst::Predicate::FCMP_UGT:
+    return LLVM::FCmpPredicate::ugt;
+  case llvm::CmpInst::Predicate::FCMP_UGE:
+    return LLVM::FCmpPredicate::uge;
+  case llvm::CmpInst::Predicate::FCMP_UNO:
+    return LLVM::FCmpPredicate::uno;
+  case llvm::CmpInst::Predicate::FCMP_UEQ:
+    return LLVM::FCmpPredicate::ueq;
+  case llvm::CmpInst::Predicate::FCMP_UNE:
+    return LLVM::FCmpPredicate::une;
+  }
+  llvm_unreachable("incorrect floating point comparison predicate");
 }
 
 static AtomicOrdering getLLVMAtomicOrdering(llvm::AtomicOrdering ordering) {
   switch (ordering) {
   case llvm::AtomicOrdering::NotAtomic:
     return LLVM::AtomicOrdering::not_atomic;
   case llvm::AtomicOrdering::Unordered:
     return LLVM::AtomicOrdering::unordered;
case llvm::Instruction::ICmp: {
     Value rhs = processValue(inst->getOperand(1));
     if (!lhs || !rhs)
       return failure();
     v = b.create<ICmpOp>(
         loc, getICmpPredicate(cast<llvm::ICmpInst>(inst)->getPredicate()), lhs,
         rhs);
     return success();
   }
+  case llvm::Instruction::FCmp: {
+    Value lhs = processValue(inst->getOperand(0));
+    Value rhs = processValue(inst->getOperand(1));
+    if (!lhs || !rhs)
+      return failure();
+    instMap[inst] = b.create<FCmpOp>(
+        loc, b.getI1Type(),
+        getFCmpPredicate(cast<llvm::FCmpInst>(inst)->getPredicate()), lhs, rhs);
+    return success();
+  }
   case llvm::Instruction::Br: {
     auto *brInst = cast<llvm::BranchInst>(inst);
     OperationState state(loc,
                          brInst->isConditional() ? "llvm.cond_br" : "llvm.br");
     if (brInst->isConditional()) {
       Value condition = processValue(brInst->getCondition());
       if (!condition)
         return failure();

mlir/test/Target/LLVMIR/Import/basic.ll

define void @FPArithmetic(float %a, float %b, double %c, double %d) {
   %9 = fdiv double %c, %d
   ; CHECK: %[[a11:[0-9]+]] = llvm.frem %arg0, %arg1 : f32
   %10 = frem float %a, %b
   ; CHECK: %[[a13:[0-9]+]] = llvm.frem %arg2, %arg3 : f64
   %11 = frem double %c, %d
   ret void
 }
 
+; CHECK-LABEL: llvm.func @FPComparison(%arg0: f32, %arg1: f32)
+define void @FPComparison(float %a, float %b) {
+  ; CHECK: llvm.fcmp "_false" %arg0, %arg1
+  %1 = fcmp false float %a, %b
+  ; CHECK: llvm.fcmp "oeq" %arg0, %arg1
+  %2 = fcmp oeq float %a, %b
+  ; CHECK: llvm.fcmp "ogt" %arg0, %arg1
+  %3 = fcmp ogt float %a, %b
+  ; CHECK: llvm.fcmp "oge" %arg0, %arg1
+  %4 = fcmp oge float %a, %b
+  ; CHECK: llvm.fcmp "olt" %arg0, %arg1
+  %5 = fcmp olt float %a, %b
+  ; CHECK: llvm.fcmp "ole" %arg0, %arg1
+  %6 = fcmp ole float %a, %b
+  ; CHECK: llvm.fcmp "one" %arg0, %arg1
+  %7 = fcmp one float %a, %b
+  ; CHECK: llvm.fcmp "ord" %arg0, %arg1
+  %8 = fcmp ord float %a, %b
+  ; CHECK: llvm.fcmp "ueq" %arg0, %arg1
+  %9 = fcmp ueq float %a, %b
+  ; CHECK: llvm.fcmp "ugt" %arg0, %arg1
+  %10 = fcmp ugt float %a, %b
+  ; CHECK: llvm.fcmp "uge" %arg0, %arg1
+  %11 = fcmp uge float %a, %b
+  ; CHECK: llvm.fcmp "ult" %arg0, %arg1
+  %12 = fcmp ult float %a, %b
+  ; CHECK: llvm.fcmp "ule" %arg0, %arg1
+  %13 = fcmp ule float %a, %b
+  ; CHECK: llvm.fcmp "une" %arg0, %arg1
+  %14 = fcmp une float %a, %b
+  ; CHECK: llvm.fcmp "uno" %arg0, %arg1
+  %15 = fcmp uno float %a, %b
+  ; CHECK: llvm.fcmp "_true" %arg0, %arg1
+  %16 = fcmp true float %a, %b
+  ret void
+}
+
+; Testing rest of the floating point constant kinds.
+; CHECK-LABEL: llvm.func @FPConstant(%arg0: f16, %arg1: bf16, %arg2: f128, %arg3: f80)
+define void @FPConstant(half %a, bfloat %b, fp128 %c, x86_fp80 %d) {
+  ; CHECK-DAG: %[[C0:.+]] = llvm.mlir.constant(7.000000e+00 : f80) : f80
+  ; CHECK-DAG: %[[C1:.+]] = llvm.mlir.constant(0.000000e+00 : f128) : f128
+  ; CHECK-DAG: %[[C2:.+]] = llvm.mlir.constant(1.000000e+00 : bf16) : bf16
+  ; CHECK-DAG: %[[C3:.+]] = llvm.mlir.constant(1.000000e+00 : f16) : f16
+
+  ; CHECK: llvm.fadd %[[C3]], %arg0  : f16
+  %1 = fadd half 1.0, %a
+  ; CHECK: llvm.fadd %[[C2]], %arg1  : bf16
+  %2 = fadd bfloat 1.0, %b
+  ; CHECK: llvm.fadd %[[C1]], %arg2  : f128
+  %3 = fadd fp128 0xL00000000000000000000000000000000, %c
+  ; CHECK: llvm.fadd %[[C0]], %arg3  : f80
+  %4 = fadd x86_fp80 0xK4001E000000000000000, %d
+  ret void
+}
+
 ;
 ; Functions as constants.
 ;
 
 ; Calling the function that has not been defined yet.
 ; CHECK-LABEL: @precaller
 define i32 @precaller() {
   %1 = alloca i32 ()*