From bd95d2ae66be16a8d5d4281e28347fba0ed625b3 Mon Sep 17 00:00:00 2001
From: gingerBill <gingerBill@users.noreply.github.com>
Date: Mon, 17 Aug 2026 13:32:28 +0100
Subject: [PATCH] Add `asm` directive `#align N`

---
 src/check_asm.cpp        | 31 +++++++++++++++++++++++++++++++
 src/llvm_backend_asm.cpp |  9 +++++++++
 2 files changed, 40 insertions(+)

diff --git a/src/check_asm.cpp b/src/check_asm.cpp
index ea50aa45e..c847b1932 100644
--- a/src/check_asm.cpp
+++ b/src/check_asm.cpp
@@ -1515,7 +1515,38 @@ gb_internal void check_asm_template(AsmCtx *asm_ctx, CheckerContext *ctx, Entity
 						continue;
 					}
 				}
+			} else if (name == "align") {
+				if (dir->operands.count != 1) {
+					error(dir->name, "Expected 1 integer for the asm directive #%.*s", LIT(name));
+					break;
+				}
+				array_clear(&operands);
+				for (Ast *expr : dir->operands) {
+					Operand operand = {};
+					check_asm_instruction_operand(asm_ctx, ctx, entity, &operand, expr, /*allow_memory_operands*/true);
+					array_add(&operands, operand);
+				}
+				for (auto const &op : operands) {
+					if (op.mode != Addressing_Constant) {
+						error(op.expr, "Expected a power-of-two integer for the asm directive #%.*s", LIT(name));
+						continue;
+					}
+					ExactValue ev = exact_value_to_integer(op.value);
+					if (ev.kind != ExactValue_Integer) {
+						error(op.expr, "Expected a power-of-two integer for the asm directive #%.*s", LIT(name));
+						continue;
+					}
+					i64 i = exact_value_to_i64(ev);
+					if (i < 0 || !is_power_of_two(i)) {
+						error(op.expr, "Expected a power-of-two integer for the asm directive #%.*s, got %lld", LIT(name), cast(long long)i);
+						continue;
+					}
+				}
+
+			} else {
+				error(dir->name, "Unknown asm directive: #%.*s", LIT(name));
 			}
+
 		case_end;
 
 		default:
diff --git a/src/llvm_backend_asm.cpp b/src/llvm_backend_asm.cpp
index 19a902c99..5cca6d89b 100644
--- a/src/llvm_backend_asm.cpp
+++ b/src/llvm_backend_asm.cpp
@@ -495,6 +495,15 @@ struct lbAsmGenerate_amd64 : lbAsmGenerate {
 						asm_string = gb_string_append_fmt(asm_string, "%d", cast(int)i);
 						op_index += 1;
 					}
+				} else if (name == "align") {
+					asm_string = gb_string_appendc(asm_string, ".p2align ");
+					GB_ASSERT(dir->operands.count == 1);
+					auto const &op = dir->operands[0];
+					ExactValue ev = exact_value_to_integer(op->tav.value);
+					GB_ASSERT(ev.kind == ExactValue_Integer);
+					u64 i = exact_value_to_u64(ev);
+					u64 i_log2 = floor_log2(i);
+					asm_string = gb_string_append_fmt(asm_string, "%llu", cast(unsigned long long)i_log2);
 				} else {
 					GB_PANIC("Invalid asm directive: %.*s", LIT(name));
 				}