[CIR][HIP] Proper Handling of address spaces in ptr-diff

clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

@@ -1513,17 +1513,41 @@ mlir::Value ScalarExprEmitter::emitSub(const BinOpInfo &Ops) {
   if (!mlir::isa<cir::PointerType>(Ops.RHS.getType()))
     return emitPointerArithmetic(CGF, Ops, /*isSubtraction=*/true);
 
-  // Otherwise, this is a pointer subtraction
+  const BinaryOperator *Expr = cast<BinaryOperator>(Ops.E);
+  QualType ElementType = Expr->getLHS()->getType()->getPointeeType();
 
-  // Do the raw subtraction part.
-  //
+  // Check if this is a VLA pointee type.
+  if (const auto *VLA = CGF.getContext().getAsVariableArrayType(ElementType)) {
+    llvm_unreachable("NYI: CIR ptrdiff on VLA pointee");
+  }
   // TODO(cir): note for LLVM lowering out of this; when expanding this into
   // LLVM we shall take VLA's, division by element size, etc.
+  // now we just ensure that all pointers are on the proper address space.
+  mlir::Value LHS = Ops.LHS;
+  mlir::Value RHS = Ops.RHS;
+  mlir::Location loc = CGF.getLoc(Ops.Loc);
+
+  cir::PointerType LHSPtrTy = mlir::dyn_cast<cir::PointerType>(LHS.getType());
+  cir::PointerType RHSPtrTy = mlir::dyn_cast<cir::PointerType>(RHS.getType());
+
+  if (LHSPtrTy && RHSPtrTy) {
+    auto LHSAS = LHSPtrTy.getAddrSpace();
+    auto RHSAS = RHSPtrTy.getAddrSpace();
+
+    if (LHSAS != RHSAS) {
+      // Different address spaces → use addrspacecast
+      RHS = Builder.createAddrSpaceCast(RHS, LHSPtrTy);
+    } else if (LHSPtrTy != RHSPtrTy) {
+      // Same addrspace but different pointee/type → bitcast is fine
+      RHS = Builder.createBitcast(RHS, LHSPtrTy);
+    }
+  }
+  // Do the raw subtraction part.
   //
   // See more in `EmitSub` in CGExprScalar.cpp.
   assert(!cir::MissingFeatures::llvmLoweringPtrDiffConsidersPointee());
   return cir::PtrDiffOp::create(Builder, CGF.getLoc(Ops.Loc), CGF.PtrDiffTy,
-                                Ops.LHS, Ops.RHS);
+                                LHS, RHS);
 }
 
 mlir::Value ScalarExprEmitter::emitShl(const BinOpInfo &Ops) {

clang/test/CIR/CodeGen/HIP/ptr-diff.cpp

@@ -0,0 +1,60 @@
+#include "cuda.h"
+
+// RUN: %clang_cc1 -triple=amdgcn-amd-amdhsa -x hip -fclangir \
+// RUN:            -fcuda-is-device -fhip-new-launch-api \
+// RUN:            -I%S/../Inputs/ -emit-cir %s -o %t.ll
+// RUN: FileCheck --check-prefix=CIR-DEVICE --input-file=%t.ll %s
+
+// RUN: %clang_cc1 -triple=amdgcn-amd-amdhsa -x hip -fclangir \
+// RUN:            -fcuda-is-device -fhip-new-launch-api \
+// RUN:            -I%S/../Inputs/ -emit-llvm %s -o %t.ll
+// RUN: FileCheck --check-prefix=LLVM-DEVICE --input-file=%t.ll %s
+
+// RUN: %clang_cc1 -triple=amdgcn-amd-amdhsa -x hip  \
+// RUN:            -fcuda-is-device -fhip-new-launch-api \
+// RUN:            -I%S/../Inputs/ -emit-llvm %s -o %t.ll
+// RUN: FileCheck --check-prefix=OGCG-DEVICE --input-file=%t.ll %s
+
+__device__ int ptr_diff() {
+  const char c_str[] = "c-string"; 
+  const char* len =  c_str;  
+  return c_str - len;
+}
+
+
+// CIR-DEVICE: %[[#LenLocalAddr:]] = cir.alloca !cir.ptr<!s8i>, !cir.ptr<!cir.ptr<!s8i>>, ["len", init]
+// CIR-DEVICE: %[[#GlobalPtr:]] = cir.get_global @_ZZ8ptr_diffvE5c_str : !cir.ptr<!cir.array<!s8i x 9>, addrspace(offload_constant)>
+// CIR-DEVICE: %[[#CastDecay:]] = cir.cast array_to_ptrdecay %[[#GlobalPtr]] : !cir.ptr<!cir.array<!s8i x 9>, addrspace(offload_constant)>
+// CIR-DEVICE: %[[#LenLocalAddrCast:]] = cir.cast bitcast %[[#LenLocalAddr]] : !cir.ptr<!cir.ptr<!s8i>> -> !cir.ptr<!cir.ptr<!s8i, addrspace(offload_constant)>>
+// CIR-DEVICE: cir.store align(8) %[[#CastDecay]], %[[#LenLocalAddrCast]] : !cir.ptr<!s8i, addrspace(offload_constant)>, !cir.ptr<!cir.ptr<!s8i, addrspace(offload_constant)>>
+// CIR-DEVICE: %[[#CStr:]] = cir.cast array_to_ptrdecay %[[#GlobalPtr]] : !cir.ptr<!cir.array<!s8i x 9>, addrspace(offload_constant)> -> !cir.ptr<!s8i, addrspace(offload_constant)>
+// CIR-DEVICE: %[[#LoadedLenAddr:]] = cir.load align(8) %[[#LenLocalAddr]] : !cir.ptr<!cir.ptr<!s8i>>, !cir.ptr<!s8i> loc(#loc7)
+// CIR-DEVICE: %[[#AddrCast:]] = cir.cast address_space %[[#LoadedLenAddr]] : !cir.ptr<!s8i> -> !cir.ptr<!s8i, addrspace(offload_constant)>
+// CIR-DEVICE: %[[#DIFF:]] = cir.ptr_diff %[[#CStr]], %[[#AddrCast]] : !cir.ptr<!s8i, addrspace(offload_constant)>
+
+// LLVM-DEVICE: define dso_local i32 @_Z8ptr_diffv()
+// LLVM-DEVICE: %[[#GlobalPtrAddr:]] = alloca i32, i64 1, align 4, addrspace(5)
+// LLVM-DEVICE: %[[#GlobalPtrCast:]] = addrspacecast ptr addrspace(5) %[[#GlobalPtrAddr]] to ptr
+// LLVM-DEVICE: %[[#LenLocalAddr:]] = alloca ptr, i64 1, align 8, addrspace(5)
+// LLVM-DEVICE: %[[#LenLocalAddrCast:]] = addrspacecast ptr addrspace(5) %[[#LenLocalAddr]] to ptr
+// LLVM-DEVICE: store ptr addrspace(4) @_ZZ8ptr_diffvE5c_str, ptr %[[#LenLocalAddrCast]], align 8
+// LLVM-DEVICE: %[[#LoadedAddr:]] = load ptr, ptr %[[#LenLocalAddrCast]], align 8
+// LLVM-DEVICE: %[[#CastedVal:]] = addrspacecast ptr %[[#LoadedAddr]] to ptr addrspace(4)
+// LLVM-DEVICE: %[[#IntVal:]] = ptrtoint ptr addrspace(4) %[[#CastedVal]] to i64
+// LLVM-DEVICE: %[[#SubVal:]] = sub i64 ptrtoint (ptr addrspace(4) @_ZZ8ptr_diffvE5c_str to i64), %[[#IntVal]]
+
+// OGCG-DEVICE: define dso_local noundef i32 @_Z8ptr_diffv() #0
+// OGCG-DEVICE: %[[RETVAL:.*]] = alloca i32, align 4, addrspace(5)
+// OGCG-DEVICE: %[[C_STR:.*]] = alloca [9 x i8], align 1, addrspace(5)
+// OGCG-DEVICE: %[[LEN:.*]] = alloca ptr, align 8, addrspace(5)
+// OGCG-DEVICE: %[[RETVAL_ASCAST:.*]] = addrspacecast ptr addrspace(5) %[[RETVAL]] to ptr
+// OGCG-DEVICE: %[[C_STR_ASCAST:.*]] = addrspacecast ptr addrspace(5) %[[C_STR]] to ptr
+// OGCG-DEVICE: %[[LEN_ASCAST:.*]] = addrspacecast ptr addrspace(5) %[[LEN]] to ptr
+// OGCG-DEVICE: %[[ARRAYDECAY:.*]] = getelementptr inbounds [9 x i8], ptr %[[C_STR_ASCAST]], i64 0, i64 0
+// OGCG-DEVICE: store ptr %[[ARRAYDECAY]], ptr %[[LEN_ASCAST]], align 8
+// OGCG-DEVICE: %[[ARRAYDECAY1:.*]] = getelementptr inbounds [9 x i8], ptr %[[C_STR_ASCAST]], i64 0, i64 0
+// OGCG-DEVICE: %[[LOADED:.*]] = load ptr, ptr %[[LEN_ASCAST]], align 8
+// OGCG-DEVICE: %[[LHS:.*]] = ptrtoint ptr %[[ARRAYDECAY1]] to i64
+// OGCG-DEVICE: %[[RHS:.*]] = ptrtoint ptr %[[LOADED]] to i64
+// OGCG-DEVICE: %[[SUB:.*]] = sub i64 %[[LHS]], %[[RHS]]
+// OGCG-DEVICE: %[[CONV:.*]] = trunc i64 %[[SUB]] to i32