[PATCH] D104718: [OpaquePtr] Support changing load type in InstCombine

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: aeubanks, dblaikie.
Herald added subscribers: dexonsmith, hiraditya.
nikic requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

When the load type is changed to `ptr`, we need the load pointer type to also be `ptr`, because it's not allowed to create a pointer to an opaque pointer. This is achieved by adjusting the `getPointerTo()` API to return an opaque pointer for an opaque pointer base type.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104718

Files:
  llvm/lib/IR/Type.cpp
  llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
  llvm/test/Transforms/InstCombine/opaque-ptr.ll


Index: llvm/test/Transforms/InstCombine/opaque-ptr.ll
===================================================================
--- llvm/test/Transforms/InstCombine/opaque-ptr.ll
+++ llvm/test/Transforms/InstCombine/opaque-ptr.ll
@@ -63,3 +63,24 @@
 ;
   ret ptr getelementptr (i8, ptr bitcast (i8* @g to ptr), i32 3)
 }
+
+define ptr @load_bitcast_1(ptr %a) {
+; CHECK-LABEL: @load_bitcast_1(
+; CHECK-NEXT:    [[B1:%.*]] = load ptr, ptr [[A:%.*]], align 8
+; CHECK-NEXT:    ret ptr [[B1]]
+;
+  %b = load i8*, ptr %a
+  %c = bitcast i8* %b to ptr
+  ret ptr %c
+}
+
+define ptr @load_bitcast_2(ptr %a) {
+; CHECK-LABEL: @load_bitcast_2(
+; CHECK-NEXT:    [[C1:%.*]] = load ptr, ptr [[A:%.*]], align 8
+; CHECK-NEXT:    ret ptr [[C1]]
+;
+  %b = bitcast ptr %a to i8**
+  %c = load i8*, i8** %b
+  %d = bitcast i8* %c to ptr
+  ret ptr %d
+}
Index: llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -463,11 +463,11 @@
 
   Value *Ptr = LI.getPointerOperand();
   unsigned AS = LI.getPointerAddressSpace();
+  Type *NewPtrTy = NewTy->getPointerTo(AS);
   Value *NewPtr = nullptr;
   if (!(match(Ptr, m_BitCast(m_Value(NewPtr))) &&
-        NewPtr->getType()->getPointerElementType() == NewTy &&
-        NewPtr->getType()->getPointerAddressSpace() == AS))
-    NewPtr = Builder.CreateBitCast(Ptr, NewTy->getPointerTo(AS));
+        NewPtr->getType() == NewPtrTy))
+    NewPtr = Builder.CreateBitCast(Ptr, NewPtrTy);
 
   LoadInst *NewLoad = Builder.CreateAlignedLoad(
       NewTy, NewPtr, LI.getAlign(), LI.isVolatile(), LI.getName() + Suffix);
Index: llvm/lib/IR/Type.cpp
===================================================================
--- llvm/lib/IR/Type.cpp
+++ llvm/lib/IR/Type.cpp
@@ -725,8 +725,13 @@
   setSubclassData(AddrSpace);
 }
 
-PointerType *Type::getPointerTo(unsigned addrs) const {
-  return PointerType::get(const_cast<Type*>(this), addrs);
+PointerType *Type::getPointerTo(unsigned AddrSpace) const {
+  // Pointer to opaque pointer is opaque pointer.
+  if (auto *PTy = dyn_cast<PointerType>(this))
+    if (PTy->isOpaque())
+      return PointerType::get(getContext(), AddrSpace);
+
+  return PointerType::get(const_cast<Type*>(this), AddrSpace);
 }
 
 bool PointerType::isValidElementType(Type *ElemTy) {


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