llvm: unify lowering via Resolver and Cursor; remove non-sealed PHI wiring; apply Resolver to extern/call/boxcall/arrays/maps/mem; add llvmlite harness docs; add LLVM layer overview; add LoopForm preheader

src/llvm_py/instructions/const.py

@@ -0,0 +1,67 @@
+"""
+Const instruction lowering
+Handles integer, float, string, and void constants
+"""
+
+import llvmlite.ir as ir
+from typing import Dict, Any
+
+def lower_const(
+    builder: ir.IRBuilder,
+    module: ir.Module,
+    dst: int,
+    value: Dict[str, Any],
+    vmap: Dict[int, ir.Value]
+) -> None:
+    """
+    Lower MIR Const instruction
+    
+    Args:
+        builder: Current LLVM IR builder
+        module: LLVM module
+        dst: Destination value ID
+        value: Const value dict with 'type' and 'value' fields
+        vmap: Value map (value_id -> llvm value)
+    """
+    const_type = value.get('type', 'void')
+    const_val = value.get('value')
+    
+    if const_type == 'i64':
+        # Integer constant
+        i64 = ir.IntType(64)
+        llvm_val = ir.Constant(i64, int(const_val))
+        vmap[dst] = llvm_val
+        
+    elif const_type == 'f64':
+        # Float constant
+        f64 = ir.DoubleType()
+        llvm_val = ir.Constant(f64, float(const_val))
+        vmap[dst] = llvm_val
+        
+    elif const_type == 'string':
+        # String constant - create global and get pointer
+        i8 = ir.IntType(8)
+        str_val = str(const_val)
+        str_const = ir.Constant.literal_string(str_val.encode('utf-8') + b'\0')
+        
+        # Create global string constant
+        global_name = f".str.{dst}"
+        global_str = ir.GlobalVariable(module, str_const.type, name=global_name)
+        global_str.initializer = str_const
+        global_str.linkage = 'private'
+        global_str.global_constant = True
+        
+        # Get pointer to first element
+        indices = [ir.Constant(ir.IntType(32), 0), ir.Constant(ir.IntType(32), 0)]
+        ptr = builder.gep(global_str, indices, name=f"str_ptr_{dst}")
+        vmap[dst] = ptr
+        
+    elif const_type == 'void':
+        # Void/null constant - use i64 zero
+        i64 = ir.IntType(64)
+        vmap[dst] = ir.Constant(i64, 0)
+        
+    else:
+        # Unknown type - default to i64 zero
+        i64 = ir.IntType(64)
+        vmap[dst] = ir.Constant(i64, 0)