[llvm] [CodeGen] Forbid passing a PointerType to MVT::getVT and EVT::getEVT (PR #92671)

[Jessica Clarke via llvm-commits]

https://github.com/jrtc27 updated https://github.com/llvm/llvm-project/pull/92671

>From c66ee009729fdf56aef1b53efe3588ef4e387e09 Mon Sep 17 00:00:00 2001
From: Jessica Clarke <jrtc27 at jrtc27.com>
Date: Sat, 18 May 2024 21:18:38 +0100
Subject: [PATCH] [CodeGen] Forbid passing a PointerType to MVT::getVT and
 EVT::getEVT

There is the expectation throughout CodeGen that, for types representing
"real" values, the MVT or EVT is self-contained. However, MVT::iPTR is
challenging, because it has no address space, and even if it did, there
often is no DataLayout immediately accessible to determine what actually
is the underlying type.

Historically it was documented as being TableGen-only, but that was lost
in 631bfdbee5b45eda9f99dff6a716d63c5698e4bd's conversion to using the
generated defines. Let's preserve that intent by not allowing it to
originate through accidental calls to get(E)VT with a PointerType. If
you need to support that, be sure to use something like TargetLowering's
getValueType, which takes a DataLayout and can map pointers to their
concrete MVTs.
---
 llvm/include/llvm/CodeGen/ValueTypes.h            |  4 ++--
 llvm/include/llvm/CodeGenTypes/MachineValueType.h |  6 +++---
 llvm/lib/CodeGen/ValueTypes.cpp                   | 13 ++++++-------
 3 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/ValueTypes.h b/llvm/include/llvm/CodeGen/ValueTypes.h
index b66c66d1bfc45..a4d57fba7a7a0 100644
--- a/llvm/include/llvm/CodeGen/ValueTypes.h
+++ b/llvm/include/llvm/CodeGen/ValueTypes.h
@@ -488,8 +488,8 @@ namespace llvm {
     Type *getTypeForEVT(LLVMContext &Context) const;
 
     /// Return the value type corresponding to the specified type.
-    /// This returns all pointers as iPTR.  If HandleUnknown is true, unknown
-    /// types are returned as Other, otherwise they are invalid.
+    /// If HandleUnknown is true, unknown types are returned as Other,
+    /// otherwise they are invalid.
     static EVT getEVT(Type *Ty, bool HandleUnknown = false);
 
     intptr_t getRawBits() const {
diff --git a/llvm/include/llvm/CodeGenTypes/MachineValueType.h b/llvm/include/llvm/CodeGenTypes/MachineValueType.h
index 9aceb9896021c..f3280d0276399 100644
--- a/llvm/include/llvm/CodeGenTypes/MachineValueType.h
+++ b/llvm/include/llvm/CodeGenTypes/MachineValueType.h
@@ -476,9 +476,9 @@ namespace llvm {
       return getVectorVT(VT, EC.getKnownMinValue());
     }
 
-    /// Return the value type corresponding to the specified type.  This returns
-    /// all pointers as iPTR.  If HandleUnknown is true, unknown types are
-    /// returned as Other, otherwise they are invalid.
+    /// Return the value type corresponding to the specified type.
+    /// If HandleUnknown is true, unknown types are returned as Other,
+    /// otherwise they are invalid.
     static MVT getVT(Type *Ty, bool HandleUnknown = false);
 
   public:
diff --git a/llvm/lib/CodeGen/ValueTypes.cpp b/llvm/lib/CodeGen/ValueTypes.cpp
index 58db686ec7d57..38d2438f76b9d 100644
--- a/llvm/lib/CodeGen/ValueTypes.cpp
+++ b/llvm/lib/CodeGen/ValueTypes.cpp
@@ -579,9 +579,9 @@ Type *EVT::getTypeForEVT(LLVMContext &Context) const {
   // clang-format on
 }
 
-/// Return the value type corresponding to the specified type.  This returns all
-/// pointers as MVT::iPTR.  If HandleUnknown is true, unknown types are returned
-/// as Other, otherwise they are invalid.
+/// Return the value type corresponding to the specified type.
+/// If HandleUnknown is true, unknown types are returned as Other, otherwise
+/// they are invalid.
 MVT MVT::getVT(Type *Ty, bool HandleUnknown){
   assert(Ty != nullptr && "Invalid type");
   switch (Ty->getTypeID()) {
@@ -611,7 +611,6 @@ MVT MVT::getVT(Type *Ty, bool HandleUnknown){
   case Type::X86_AMXTyID:   return MVT(MVT::x86amx);
   case Type::FP128TyID:     return MVT(MVT::f128);
   case Type::PPC_FP128TyID: return MVT(MVT::ppcf128);
-  case Type::PointerTyID:   return MVT(MVT::iPTR);
   case Type::FixedVectorTyID:
   case Type::ScalableVectorTyID: {
     VectorType *VTy = cast<VectorType>(Ty);
@@ -622,9 +621,9 @@ MVT MVT::getVT(Type *Ty, bool HandleUnknown){
   }
 }
 
-/// getEVT - Return the value type corresponding to the specified type.  This
-/// returns all pointers as MVT::iPTR.  If HandleUnknown is true, unknown types
-/// are returned as Other, otherwise they are invalid.
+/// getEVT - Return the value type corresponding to the specified type.
+/// If HandleUnknown is true, unknown types are returned as Other, otherwise
+/// they are invalid.
 EVT EVT::getEVT(Type *Ty, bool HandleUnknown){
   switch (Ty->getTypeID()) {
   default: