[ARM GlobalISel] Legalize G_FPEXT and G_FPTRUNC

Mark G_FPEXT and G_FPTRUNC as legal or libcall, depending on hardware
support, but only for conversions between float and double.

Also add the necessary boilerplate so that the LegalizerHelper can
introduce the required libcalls. This also works only for float and
double, but isn't too difficult to extend when the need arises.

llvm-svn: 322651

1 files changed, 47 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 200d6b8abec..f1cb5c0ad02 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -126,6 +126,7 @@ llvm::createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
   return LegalizerHelper::Legalized;
 }
 
+// Useful for libcalls where all operands have the same type.
 static LegalizerHelper::LegalizeResult
 simpleLibcall(MachineInstr &MI, MachineIRBuilder &MIRBuilder, unsigned Size,
               Type *OpType) {
@@ -138,6 +139,28 @@ simpleLibcall(MachineInstr &MI, MachineIRBuilder &MIRBuilder, unsigned Size,
                        Args);
 }
 
+static RTLIB::Libcall getConvRTLibDesc(unsigned Opcode, Type *ToType,
+                                       Type *FromType) {
+  auto ToMVT = MVT::getVT(ToType);
+  auto FromMVT = MVT::getVT(FromType);
+
+  switch (Opcode) {
+  case TargetOpcode::G_FPEXT:
+    return RTLIB::getFPEXT(FromMVT, ToMVT);
+  case TargetOpcode::G_FPTRUNC:
+    return RTLIB::getFPROUND(FromMVT, ToMVT);
+  }
+  llvm_unreachable("Unsupported libcall function");
+}
+
+static LegalizerHelper::LegalizeResult
+conversionLibcall(MachineInstr &MI, MachineIRBuilder &MIRBuilder, Type *ToType,
+                  Type *FromType) {
+  RTLIB::Libcall Libcall = getConvRTLibDesc(MI.getOpcode(), ToType, FromType);
+  return createLibcall(MIRBuilder, Libcall, {MI.getOperand(0).getReg(), ToType},
+                       {{MI.getOperand(1).getReg(), FromType}});
+}
+
 LegalizerHelper::LegalizeResult
 LegalizerHelper::libcall(MachineInstr &MI) {
   LLT LLTy = MRI.getType(MI.getOperand(0).getReg());
@@ -172,6 +195,30 @@ LegalizerHelper::libcall(MachineInstr &MI) {
       return Status;
     break;
   }
+  case TargetOpcode::G_FPEXT: {
+    // FIXME: Support other floating point types (half, fp128 etc)
+    unsigned FromSize = MRI.getType(MI.getOperand(1).getReg()).getSizeInBits();
+    unsigned ToSize = MRI.getType(MI.getOperand(0).getReg()).getSizeInBits();
+    if (ToSize != 64 || FromSize != 32)
+      return UnableToLegalize;
+    LegalizeResult Status = conversionLibcall(
+        MI, MIRBuilder, Type::getDoubleTy(Ctx), Type::getFloatTy(Ctx));
+    if (Status != Legalized)
+      return Status;
+    break;
+  }
+  case TargetOpcode::G_FPTRUNC: {
+    // FIXME: Support other floating point types (half, fp128 etc)
+    unsigned FromSize = MRI.getType(MI.getOperand(1).getReg()).getSizeInBits();
+    unsigned ToSize = MRI.getType(MI.getOperand(0).getReg()).getSizeInBits();
+    if (ToSize != 32 || FromSize != 64)
+      return UnableToLegalize;
+    LegalizeResult Status = conversionLibcall(
+        MI, MIRBuilder, Type::getFloatTy(Ctx), Type::getDoubleTy(Ctx));
+    if (Status != Legalized)
+      return Status;
+    break;
+  }
   }
 
   MI.eraseFromParent();