Address feedback, and fix deref to match allocated type

Not only was the type used in the expression potentially different than
the location op used, but we were treating all variables as being "ptr"
type, rather than the actual allocated type.

Author: slinder1

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

@@ -15,7 +15,7 @@ function add(a, b) result(ret)
 !CHECK: define float @add_({{.*}}){{.*}}!dbg ![[SP:[0-9]+]] {
 !CHECK: #dbg_declare({{.*}}, ![[A:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), !{{.*}})
 !CHECK: #dbg_declare({{.*}}, ![[B:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), !{{.*}})
-!CHECK: #dbg_declare({{.*}}, ![[RET:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr)), !{{.*}})
+!CHECK: #dbg_declare({{.*}}, ![[RET:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(float)), !{{.*}})
 !CHECK: }
 !CHECK: ![[SP]] = {{.*}}!DISubprogram(name: "add"{{.*}})
 !CHECK: ![[A]] = !DILocalVariable(name: "a", arg: 1, scope: ![[SP]]{{.*}})

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -5792,14 +5792,13 @@ static void updateDebugInfoForDeclareTargetFunctions(
     if (DR->getNumVariableLocationOps() != 1u)
       return;
     auto Loc = DR->getVariableLocationOp(0u);
-    llvm::Type *Ty = Loc->getType();
-    if (auto *Ref = dyn_cast<llvm::AddrSpaceCastInst>(Loc)) {
-      DR->replaceVariableLocationOp(0u, Loc->stripPointerCasts());
-      Ty = Ref->getPointerOperand()->getType();
-    }
+    if (!isa<llvm::AllocaInst>(Loc->stripPointerCasts()))
+      return;
+    llvm::AllocaInst *AI = cast<llvm::AllocaInst>(Loc->stripPointerCasts());
+    DR->replaceVariableLocationOp(0u, AI);
     llvm::DIExprBuilder EB(Fn->getContext());
-    EB.append<llvm::DIOp::Arg>(0u, Ty);
-    EB.append<llvm::DIOp::Deref>(Loc->getType());
+    EB.append<llvm::DIOp::Arg>(0u, AI->getType());
+    EB.append<llvm::DIOp::Deref>(AI->getAllocatedType());
     DR->setExpression(EB.intoExpression());
   };