Global structs with array members not being initialized.

[blucia0a]

This issue is about static initializers for struct fields. I have a struct that contains an array. I have a global instance of the struct and I am attempting to initialize an array that is a member of that struct. The minimal example below illustrates the problem.

>$cat staticinit.c
typedef struct t_t{
  int a[1];
} t;

t o1 = {.a = {1}};

int f(){
  return o1.a[0];
}

When I build with cgeist, I see the following output:

>$ ../mlir-build/bin/cgeist -S --function=* ./staticinit.c -o staticinit.mlir
VarDecl 0x55e2a204b4b0 <./staticinit.c:5:1, col:17> col:3 used o1 't':'struct t_t' cinit
`-InitListExpr 0x55e2a204b6b8 <col:8, col:17> 't':'struct t_t'
  `-InitListExpr 0x55e2a204b710 <col:14, col:16> 'int[1]'
    `-IntegerLiteral 0x55e2a204b560 <col:15> 'int' 1
InitListExpr 0x55e2a204b6b8 't':'struct t_t'
`-InitListExpr 0x55e2a204b710 'int[1]'
  `-IntegerLiteral 0x55e2a204b560 'int' 1
 warning not initializing global: o1

And inspecting the resultant MLIR, I see that, indeed, my global o1 is being left uninitialized.

$ cat staticinit.mlir
module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<"dlti.endianness", "little">, #dlti.dl_entry<i64, dense<64> : vector<2xi32>>, #dlti.dl_entry<f80, dense<128> : vector<2xi32>>, #dlti.dl_entry<i1, dense<8> : vector<2xi32>>, #dlti.dl_entry<i8, dense<8> : vector<2xi32>>, #dlti.dl_entry<i16, dense<16> : vector<2xi32>>, #dlti.dl_entry<i32, dense<32> : vector<2xi32>>, #dlti.dl_entry<f16, dense<16> : vector<2xi32>>, #dlti.dl_entry<f64, dense<64> : vector<2xi32>>, #dlti.dl_entry<f128, dense<128> : vector<2xi32>>>, llvm.data_layout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128", llvm.target_triple = "x86_64-unknown-linux-gnu", "polygeist.target-cpu" = "x86-64", "polygeist.target-features" = "+cx8,+fxsr,+mmx,+sse,+sse2,+x87", "polygeist.tune-cpu" = "generic"} {
  memref.global @o1 : memref<1x!llvm.struct<(array<1 x i32>)>> = uninitialized
  func.func @f() -> i32 attributes {llvm.linkage = #llvm.linkage<external>} {
    %0 = memref.get_global @o1 : memref<1x!llvm.struct<(array<1 x i32>)>>
    %1 = "polygeist.memref2pointer"(%0) : (memref<1x!llvm.struct<(array<1 x i32>)>>) -> !llvm.ptr<struct<(array<1 x i32>)>>
    %2 = llvm.getelementptr %1[0, 0] : (!llvm.ptr<struct<(array<1 x i32>)>>) -> !llvm.ptr<array<1 x i32>>
    %3 = llvm.bitcast %2 : !llvm.ptr<array<1 x i32>> to !llvm.ptr<i32>
    %4 = llvm.load %3 : !llvm.ptr<i32>
    return %4 : i32
  }
}

The important line in that output is this one:

memref.global @o1 : memref<1x!llvm.struct<(array<1 x i32>)>> = uninitialized

The behavior that I would expect here is that the global would be initialized. It seems like that warning should be a fail-stop condition. As it is, programs that produce that warning during compilation are miscompiled, with their globals left uninitialized.