From de0a3e0ab986f6ea9c73315a8405103a4e147bb8 Mon Sep 17 00:00:00 2001
From: gingerBill <bill@gingerbill.org>
Date: Fri, 3 Feb 2023 15:07:44 +0000
Subject: Minor change to `byval` for readonly parameters

---
 src/llvm_backend_utility.cpp | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

(limited to 'src/llvm_backend_utility.cpp')

diff --git a/src/llvm_backend_utility.cpp b/src/llvm_backend_utility.cpp
index dbed32b82..a4ef61531 100644
--- a/src/llvm_backend_utility.cpp
+++ b/src/llvm_backend_utility.cpp
@@ -868,6 +868,45 @@ gb_internal lbValue lb_address_from_load(lbProcedure *p, lbValue value) {
 	return {};
 }
 
+gb_internal lbValue lb_address_from_load_if_readonly_parameter(lbProcedure *p, lbValue x) {
+	if (!LLVMIsALoadInst(x.value)) {
+		return {};
+	}
+
+	LLVMValueRef optr = LLVMGetOperand(x.value, 0);
+	while (optr && LLVMIsABitCastInst(optr)) {
+		optr = LLVMGetOperand(optr, 0);
+	}
+	LLVMAttributeIndex param_index = 1;
+	if (p->return_ptr.addr.value) {
+		param_index++;
+	}
+
+	bool is_parameter = false;
+	for (LLVMValueRef param : p->raw_input_parameters) {
+		if (param == optr) {
+			is_parameter = true;
+			break;
+		}
+		param_index++;
+	}
+	if (is_parameter) {
+		unsigned readonly_attr_kind = LLVMGetEnumAttributeKindForName("readonly", 8);
+		unsigned n = LLVMGetAttributeCountAtIndex(p->value, param_index);
+		if (n) {
+			TEMPORARY_ALLOCATOR_GUARD();
+			LLVMAttributeRef *attrs = gb_alloc_array(temporary_allocator(), LLVMAttributeRef, n);
+			LLVMGetAttributesAtIndex(p->value, param_index, attrs);
+			for (unsigned i = 0; i < n; i++) {
+				if (LLVMGetEnumAttributeKind(attrs[i]) == readonly_attr_kind) {
+					return lb_address_from_load_or_generate_local(p, x);
+				}
+			}
+		}
+	}
+	return {};
+}
+
 
 gb_internal lbStructFieldRemapping lb_get_struct_remapping(lbModule *m, Type *t) {
 	t = base_type(t);
-- 
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