Remove the `x86_mmx` IR type. (#98505)

It is now translated to `<1 x i64>`, which allows the removal of a bunch
of special casing.

This _incompatibly_ changes the ABI of any LLVM IR function with
`x86_mmx` arguments or returns: instead of passing in mmx registers,
they will now be passed via integer registers. However, the real-world
incompatibility caused by this is expected to be minimal, because Clang
never uses the x86_mmx type -- it lowers `__m64` to either `<1 x i64>`
or `double`, depending on ABI.

This change does _not_ eliminate the SelectionDAG `MVT::x86mmx` type.
That type simply no longer corresponds to an IR type, and is used only
by MMX intrinsics and inline-asm operands.

Because SelectionDAGBuilder only knows how to generate the
operands/results of intrinsics based on the IR type, it thus now
generates the intrinsics with the type MVT::v1i64, instead of
MVT::x86mmx. We need to fix this before the DAG LegalizeTypes, and thus
have the X86 backend fix them up in DAGCombine. (This may be a
short-lived hack, if all the MMX intrinsics can be removed in upcoming
changes.)

Works towards issue #98272.

1 files changed, 10 insertions, 4 deletions

diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index 2087198..9b0dd5f 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -1052,8 +1052,9 @@ static std::string getMangledTypeStr(Type *Ty, bool &HasUnnamedType) {
     case Type::DoubleTyID:    Result += "f64";      break;
     case Type::X86_FP80TyID:  Result += "f80";      break;
     case Type::FP128TyID:     Result += "f128";     break;
-    case Type::PPC_FP128TyID: Result += "ppcf128";  break;
-    case Type::X86_MMXTyID:   Result += "x86mmx";   break;
+    case Type::PPC_FP128TyID:
+      Result += "ppcf128";
+      break;
     case Type::X86_AMXTyID:   Result += "x86amx";   break;
     case Type::IntegerTyID:
       Result += "i" + utostr(cast<IntegerType>(Ty)->getBitWidth());
@@ -1397,7 +1398,8 @@ static Type *DecodeFixedType(ArrayRef<Intrinsic::IITDescriptor> &Infos,
   switch (D.Kind) {
   case IITDescriptor::Void: return Type::getVoidTy(Context);
   case IITDescriptor::VarArg: return Type::getVoidTy(Context);
-  case IITDescriptor::MMX: return Type::getX86_MMXTy(Context);
+  case IITDescriptor::MMX:
+    return llvm::FixedVectorType::get(llvm::IntegerType::get(Context, 64), 1);
   case IITDescriptor::AMX: return Type::getX86_AMXTy(Context);
   case IITDescriptor::Token: return Type::getTokenTy(Context);
   case IITDescriptor::Metadata: return Type::getMetadataTy(Context);
@@ -1580,7 +1582,11 @@ static bool matchIntrinsicType(
   switch (D.Kind) {
     case IITDescriptor::Void: return !Ty->isVoidTy();
     case IITDescriptor::VarArg: return true;
-    case IITDescriptor::MMX:  return !Ty->isX86_MMXTy();
+    case IITDescriptor::MMX: {
+      FixedVectorType *VT = dyn_cast<FixedVectorType>(Ty);
+      return !VT || VT->getNumElements() != 1 ||
+             !VT->getElementType()->isIntegerTy(64);
+    }
     case IITDescriptor::AMX:  return !Ty->isX86_AMXTy();
     case IITDescriptor::Token: return !Ty->isTokenTy();
     case IITDescriptor::Metadata: return !Ty->isMetadataTy();