[OMPIRBuilder] Improve DIOp based expression generation. (llvm#2477)

Author: ronlieb

flang/test/Integration/amdgpu/debug-target-var.f90

@@ -19,8 +19,8 @@ end subroutine fff
 ! CHECK-DAG: store ptr %[[ARG2]], ptr %[[CAST2:[0-9]+]]{{.*}}
 ! CHECK-DAG: %[[CAST2]] = addrspacecast ptr addrspace(5) %[[AL2:[0-9]+]]
 ! CHECK-DAG: %[[AL2]] = alloca{{.*}}
-! CHECK-DAG: #dbg_declare(ptr %[[CAST1]], ![[X:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
-! CHECK-DAG: #dbg_declare(ptr %[[CAST2]], ![[Y:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
+! CHECK-DAG: #dbg_declare(ptr {{.*}}%[[AL1]], ![[X:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
+! CHECK-DAG: #dbg_declare(ptr {{.*}}%[[AL2]], ![[Y:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
 ! CHECK: }
 
 ! CHECK-DAG: ![[SP]] = {{.*}}!DISubprogram(name: "[[FN]]"{{.*}})

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -6986,22 +6986,17 @@ static void FixupDebugInfoForOutlinedFunction(
       // snippet) as location of variable. The AMDGPU backend drops the debug
       // info for variable in such cases. So we change the location to alloca
       // instead.
+      if (DR->getNumVariableLocationOps() != 1u)
+        return;
+      auto Loc = DR->getVariableLocationOp(0u);
       bool PassByRef = false;
-      llvm::Type *locType = nullptr;
-      for (auto Loc : DR->location_ops()) {
-        locType = Loc->getType();
-        if (llvm::LoadInst *Load = dyn_cast<llvm::LoadInst>(Loc)) {
-          DR->replaceVariableLocationOp(Loc, Load->getPointerOperand());
-          PassByRef = true;
-        }
+      if (llvm::LoadInst *Load = dyn_cast<llvm::LoadInst>(Loc)) {
+        Loc = Load->getPointerOperand();
+        PassByRef = true;
       }
       // Add DIOps based expression. Note that we generate an extra indirection
       // if an argument is mapped by reference. The first reads the pointer
       // from alloca and 2nd read the value of the variable from that pointer.
-      llvm::DIExprBuilder ExprBuilder(Builder.getContext());
-      unsigned int allocaAS = M->getDataLayout().getAllocaAddrSpace();
-      unsigned int defaultAS = M->getDataLayout().getProgramAddressSpace();
-      ExprBuilder.append<llvm::DIOp::Arg>(0u, Builder.getPtrTy(allocaAS));
       // We have 2 options for the variables that are mapped byRef.
       // 1. Use a single indirection but change the type to the reference to the
       // original type. It will show up in the debugger as
@@ -7010,10 +7005,15 @@ static void FixupDebugInfoForOutlinedFunction(
       // 2. Use double indirection and keep the original type. It will show up
       // in debugger as "x=5". This approached is used here as it is
       // consistent with the normal fortran parameters display.
-      if (PassByRef)
-        ExprBuilder.append<llvm::DIOp::Deref>(Builder.getPtrTy(defaultAS));
-      ExprBuilder.append<llvm::DIOp::Deref>(locType);
-      DR->setExpression(ExprBuilder.intoExpression());
+      if (auto AI = dyn_cast<llvm::AllocaInst>(Loc->stripPointerCasts())) {
+        DR->replaceVariableLocationOp(0u, AI);
+        llvm::DIExprBuilder ExprBuilder(Builder.getContext());
+        ExprBuilder.append<llvm::DIOp::Arg>(0u, AI->getType());
+        if (PassByRef)
+          ExprBuilder.append<llvm::DIOp::Deref>(AI->getAllocatedType());
+        ExprBuilder.append<llvm::DIOp::Deref>(AI->getAllocatedType());
+        DR->setExpression(ExprBuilder.intoExpression());
+      }
     }
 
     DR->setVariable(GetUpdatedDIVariable(OldVar, ArgNo));