1 files changed, 31 insertions, 0 deletions

diff --git a/src/codegen.cpp b/src/codegen.cpp
index 1033ed8120..08dd11800a 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -3814,6 +3814,11 @@ static LLVMValueRef get_int_builtin_fn(CodeGen *g, ZigType *int_type, BuiltinFnI
         n_args = 1;
         key.id = ZigLLVMFnIdPopCount;
         key.data.pop_count.bit_count = (uint32_t)int_type->data.integral.bit_count;
+    } else if (fn_id == BuiltinFnIdBswap) {
+        fn_name = "bswap";
+        n_args = 1;
+        key.id = ZigLLVMFnIdBswap;
+        key.data.bswap.bit_count = (uint32_t)int_type->data.integral.bit_count;
     } else {
         zig_unreachable();
     }
@@ -5098,6 +5103,29 @@ static LLVMValueRef ir_render_sqrt(CodeGen *g, IrExecutable *executable, IrInstr
     return LLVMBuildCall(g->builder, fn_val, &op, 1, "");
 }
 
+static LLVMValueRef ir_render_bswap(CodeGen *g, IrExecutable *executable, IrInstructionBswap *instruction) {
+    LLVMValueRef op = ir_llvm_value(g, instruction->op);
+    ZigType *int_type = instruction->base.value.type;
+    assert(int_type->id == ZigTypeIdInt);
+    if (int_type->data.integral.bit_count % 16 == 0) {
+        LLVMValueRef fn_val = get_int_builtin_fn(g, instruction->base.value.type, BuiltinFnIdBswap);
+        return LLVMBuildCall(g->builder, fn_val, &op, 1, "");
+    }
+    // Not an even number of bytes, so we zext 1 byte, then bswap, shift right 1 byte, truncate
+    ZigType *extended_type = get_int_type(g, int_type->data.integral.is_signed,
+            int_type->data.integral.bit_count + 8);
+    // aabbcc
+    LLVMValueRef extended = LLVMBuildZExt(g->builder, op, extended_type->type_ref, "");
+    // 00aabbcc
+    LLVMValueRef fn_val = get_int_builtin_fn(g, extended_type, BuiltinFnIdBswap);
+    LLVMValueRef swapped = LLVMBuildCall(g->builder, fn_val, &extended, 1, "");
+    // ccbbaa00
+    LLVMValueRef shifted = ZigLLVMBuildLShrExact(g->builder, swapped,
+            LLVMConstInt(extended_type->type_ref, 8, false), "");
+    // 00ccbbaa
+    return LLVMBuildTrunc(g->builder, shifted, int_type->type_ref, "");
+}
+
 static void set_debug_location(CodeGen *g, IrInstruction *instruction) {
     AstNode *source_node = instruction->source_node;
     Scope *scope = instruction->scope;
@@ -5335,6 +5363,8 @@ static LLVMValueRef ir_render_instruction(CodeGen *g, IrExecutable *executable,
             return ir_render_mark_err_ret_trace_ptr(g, executable, (IrInstructionMarkErrRetTracePtr *)instruction);
         case IrInstructionIdSqrt:
             return ir_render_sqrt(g, executable, (IrInstructionSqrt *)instruction);
+        case IrInstructionIdBswap:
+            return ir_render_bswap(g, executable, (IrInstructionBswap *)instruction);
     }
     zig_unreachable();
 }
@@ -6757,6 +6787,7 @@ static void define_builtin_fns(CodeGen *g) {
     create_builtin_fn(g, BuiltinFnIdToBytes, "sliceToBytes", 1);
     create_builtin_fn(g, BuiltinFnIdFromBytes, "bytesToSlice", 2);
     create_builtin_fn(g, BuiltinFnIdThis, "This", 0);
+    create_builtin_fn(g, BuiltinFnIdBswap, "bswap", 2);
 }
 
 static const char *bool_to_str(bool b) {