Fix list.pop() for negative arguments

Author: faze-geek

integration_tests/test_list_pop.py

@@ -4,6 +4,7 @@ def test_list_pop():
     l1: list[i32]
     l2: list[tuple[i32, f64]]
     l3: list[list[str]]
+    l4: list[i32]
     i: i32
     j: i32
     total: i32
@@ -45,6 +46,10 @@ def test_list_pop():
     assert l1.pop(len(l1) - 1) == 4
     assert l1 == [1, 2]
 
+    l4 = [1, 2, 3, 4, 5]
+    assert l4.pop(-5) == 1
+    assert l4.pop(-1) == 5
+
     total = 10
     l1 = []
     for i in range(total):

src/libasr/codegen/llvm_utils.cpp

@@ -4659,10 +4659,26 @@ namespace LCompilers {
 
         llvm::Value* end_point_ptr = get_pointer_to_current_end_point(list);
         llvm::Value* end_point = LLVM::CreateLoad(*builder, end_point_ptr);
+        llvm::Value* zero = llvm::ConstantInt::get(llvm::Type::getInt32Ty(context),
+                                                   llvm::APInt(32, 0));
+        llvm::Value* adjusted_pos = pos;
+        llvm::Value* is_negative = builder->CreateICmpSLT(pos, zero);
+        llvm::Value* abs_pos = builder->CreateSelect(is_negative,
+            builder->CreateNeg(pos),
+            pos
+        );
+        llvm::Value* is_negative_and_in_bounds = builder->CreateAnd(is_negative,
+            builder->CreateICmpULE(abs_pos, end_point)
+        );
 
+        // If the index is negative, convert it to the corresponding positive index
+        adjusted_pos = builder->CreateSelect(is_negative_and_in_bounds,
+            builder->CreateAdd(end_point, pos),
+            adjusted_pos
+        );
         llvm::AllocaInst *pos_ptr = builder0.CreateAlloca(
                                     llvm::Type::getInt32Ty(context), nullptr);
-        LLVM::CreateStore(*builder, pos, pos_ptr);
+        LLVM::CreateStore(*builder, adjusted_pos, pos_ptr);
         llvm::Value* tmp = nullptr;
 
         // Get element to return