Placement of `deref` attribute on `cir.load`

[Arthur-Chang016]

by definition of deref attribute in LifetimeCheckPass::checkLoad

// Only interested in checking deference on top of pointer types.
// Note that usually the use of the invalid address happens at the
// load or store using the result of this loadOp.

given the c++ code:

int simple = *p;

we get cir:

%11 = cir.load deref align(8) %0 : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
%12 = cir.load align(4) %11 : !cir.ptr<!s32i>, !s32i
cir.store align(4) %12, %3 : !s32i, !cir.ptr<!s32i>

however the %0 is actually the address storing p but not the p itself.
Shouldn't the deref be placed on statement %12 where the dereference actually happens.

[Arthur-Chang016]

Find the issue when looking into this issue #1549

[Arthur-Chang016]

Given the c++ code:

void test_reference_binding() {
  int *ptr;
  int &ref1 = *ptr; // only reference binding, no deref attribute
}

void test_simple_assignment() {
  int *ptr;
  int value = *ptr; // deref
}

It generates:

module @"/root/clangir/tmp/test.raw" attributes {cir.lang = #cir.lang<cxx>, cir.sob = #cir.signed_overflow_behavior<undefined>, cir.triple = "x86_64-unknown-linux-gnu", cir.type_size_info = #cir.type_size_info<char = 8, int = 32, size_t = 64>, dlti.dl_spec = #dlti.dl_spec<f80 = dense<128> : vector<2xi64>, i128 = dense<128> : vector<2xi64>, !llvm.ptr<270> = dense<32> : vector<4xi64>, i8 = dense<8> : vector<2xi64>, i16 = dense<16> : vector<2xi64>, !llvm.ptr = dense<64> : vector<4xi64>, i1 = dense<8> : vector<2xi64>, f128 = dense<128> : vector<2xi64>, f16 = dense<16> : vector<2xi64>, f64 = dense<64> : vector<2xi64>, i32 = dense<32> : vector<2xi64>, !llvm.ptr<271> = dense<32> : vector<4xi64>, i64 = dense<64> : vector<2xi64>, !llvm.ptr<272> = dense<64> : vector<4xi64>, "dlti.stack_alignment" = 128 : i64, "dlti.mangling_mode" = "e", "dlti.endianness" = "little">} {
  cir.func dso_local @_Z22test_reference_bindingv() extra(#fn_attr) {
    %0 = cir.alloca !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>, ["ptr"] {alignment = 8 : i64}
    %1 = cir.alloca !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>, ["ref1", init, const] {alignment = 8 : i64}
    %2 = cir.load deref align(8) %0 : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i> 
    cir.store align(8) %2, %1 : !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>> 
    cir.return
  }
  cir.func dso_local @_Z22test_simple_assignmentv() extra(#fn_attr) {
    %0 = cir.alloca !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>, ["ptr"] {alignment = 8 : i64} 
    %1 = cir.alloca !s32i, !cir.ptr<!s32i>, ["value", init] {alignment = 4 : i64}
    %2 = cir.load deref align(8) %0 : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
    %3 = cir.load align(4) %2 : !cir.ptr<!s32i>, !s32i
    cir.store align(4) %3, %1 : !s32i, !cir.ptr<!s32i>
    cir.return
  }
}

But should we expect to generate the cir:

module @"/root/clangir/tmp/test_reference.cpp" attributes {cir.lang = #cir.lang<cxx>, cir.sob = #cir.signed_overflow_behavior<undefined>, cir.triple = "x86_64-unknown-linux-gnu", cir.type_size_info = #cir.type_size_info<char = 8, int = 32, size_t = 64>, cir.uwtable = #cir.uwtable<async>, dlti.dl_spec = #dlti.dl_spec<i8 = dense<8> : vector<2xi64>, i1 = dense<8> : vector<2xi64>, !llvm.ptr = dense<64> : vector<4xi64>, f16 = dense<16> : vector<2xi64>, i32 = dense<32> : vector<2xi64>, i16 = dense<16> : vector<2xi64>, !llvm.ptr<272> = dense<64> : vector<4xi64>, f128 = dense<128> : vector<2xi64>, f64 = dense<64> : vector<2xi64>, f80 = dense<128> : vector<2xi64>, !llvm.ptr<270> = dense<32> : vector<4xi64>, !llvm.ptr<271> = dense<32> : vector<4xi64>, i128 = dense<128> : vector<2xi64>, i64 = dense<64> : vector<2xi64>, "dlti.endianness" = "little", "dlti.mangling_mode" = "e", "dlti.stack_alignment" = 128 : i64>} {
  cir.func dso_local @_Z22test_reference_bindingv() extra(#fn_attr) {
    %0 = cir.alloca !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>, ["ptr"] {alignment = 8 : i64}
    %1 = cir.alloca !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>, ["ref1", init, const] {alignment = 8 : i64}
    %2 = cir.load align(8) %0 : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
    cir.store align(8) %2, %1 : !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>
    cir.return
  }
  cir.func dso_local @_Z22test_simple_assignmentv() extra(#fn_attr) {
    %0 = cir.alloca !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>, ["ptr"] {alignment = 8 : i64}
    %1 = cir.alloca !s32i, !cir.ptr<!s32i>, ["value", init] {alignment = 4 : i64}
    %2 = cir.load align(8) %0 : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
    %3 = cir.load deref align(4) %2 : !cir.ptr<!s32i>, !s32i
    cir.store align(4) %3, %1 : !s32i, !cir.ptr<!s32i>
    cir.return
  }
}

The deref should only happen in %3 but not in the reference binding.

The test : CIR/CodeGen/address-space-conversion.cpp generates deref attr in reference binding.