[Bug]: Generate trap due to failure to identify return stmt in function decl body

[kumarak]

VAST version

v0.0.66

LLVM version

19

Operating system

MacOS

Description

Vast codegen fails to identify return stmt in the function body because it only looks into the last effective stmt of the scope. Ref:

vast/lib/vast/CodeGen/CodeGenFunction.cpp

Line 258 in 27d3596

operation get_last_effective_operation(block_t &block) {

It can be reproduced with following snippet of code

static unsigned int var_error;
static unsigned int var_1;

unsigned int func(void) {
    unsigned int local_c;
    goto basic_0;
  basic_3:
    return local_c;
  basic_2:
    local_c = 0U;
    goto basic_3;
  basic_0:
    if (var_error == 0U)
        goto basic_1;
    else
        goto basic_2;
  basic_1:
    local_c = var_1;
    goto basic_3;
}  

Steps to Reproduce

cat << EOF > test.c
static unsigned int var_error;
static unsigned int var_1;

unsigned int func(void) {
    unsigned int local_c;
    goto basic_0;
  basic_3:
    return local_c;
  basic_2:
    local_c = 0U;
    goto basic_3;
  basic_0:
    if (var_error == 0U)
        goto basic_1;
    else
        goto basic_2;
  basic_1:
    local_c = var_1;
    goto basic_3;
}  
EOF

// Emit hl mlir 
./tools/vast-front/vast-front -vast-emit-mlir=hl test.c -o test.mlir