[llvm] 7bb7fa1 - [OpaquePtr] Support changing load type in InstCombine

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2021-06-22T21:16:15+02:00
New Revision: 7bb7fa12e73bd3c9fb66f05825758d729dd96ba5

URL: https://github.com/llvm/llvm-project/commit/7bb7fa12e73bd3c9fb66f05825758d729dd96ba5
DIFF: https://github.com/llvm/llvm-project/commit/7bb7fa12e73bd3c9fb66f05825758d729dd96ba5.diff

LOG: [OpaquePtr] Support changing load type in InstCombine

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.

Differential Revision: https://reviews.llvm.org/D104718

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/IR/Type.h b/llvm/include/llvm/IR/Type.h
index 8f16306ab817..1cf4db599082 100644
--- a/llvm/include/llvm/IR/Type.h
+++ b/llvm/include/llvm/IR/Type.h
@@ -483,6 +483,7 @@ class Type {
 
   /// Return a pointer to the current type. This is equivalent to
   /// PointerType::get(Foo, AddrSpace).
+  /// TODO: Remove this after opaque pointer transition is complete.
   PointerType *getPointerTo(unsigned AddrSpace = 0) const;
 
 private:

diff  --git a/llvm/lib/IR/Type.cpp b/llvm/lib/IR/Type.cpp
index 914ac1d10096..8c960f614af2 100644
--- a/llvm/lib/IR/Type.cpp
+++ b/llvm/lib/IR/Type.cpp
@@ -725,8 +725,13 @@ PointerType::PointerType(LLVMContext &C, unsigned AddrSpace)
   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) {

diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index e61eadf435b3..61b0bc7320be 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -463,11 +463,11 @@ LoadInst *InstCombinerImpl::combineLoadToNewType(LoadInst &LI, Type *NewTy,
 
   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);

diff  --git a/llvm/test/Transforms/InstCombine/opaque-ptr.ll b/llvm/test/Transforms/InstCombine/opaque-ptr.ll
index 81d611408cf1..0249b9686cf2 100644
--- a/llvm/test/Transforms/InstCombine/opaque-ptr.ll
+++ b/llvm/test/Transforms/InstCombine/opaque-ptr.ll
@@ -87,3 +87,24 @@ define ptr @gep_constexpr_2(ptr %a) {
 ;
   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
+}