C6000 Embedded Application Binary Interface Application Report Literature Number: SPRAB89A September 2011–Revised March 2014 Contents 1 Introduction ...................................................................................................................... 10 1.1 ABIs for the C6000 .................................................................................................... 10 1.2 Scope .................................................................................................................... 11 1.3 ABI Variants ............................................................................................................ 12 1.4 Toolchains and Interoperability ....................................................................................... 13 1.5 Libraries ................................................................................................................. 13 1.6 Types of Object Files .................................................................................................. 13 1.7 Segments ............................................................................................................... 14 1.8 C6000 Architecture Overview ........................................................................................ 14 1.9 Reference Documents ................................................................................................ 15 1.10 Code Fragment Notation .............................................................................................. 15 2 Data Representation .......................................................................................................... 16 2.1 Basic Types ............................................................................................................. 16 2.2 Data in Registers ....................................................................................................... 17 2.3 Data in Memory ........................................................................................................ 17 2.4 Complex Types ......................................................................................................... 18 2.5 Structures and Unions ................................................................................................. 18 2.6 Arrays .................................................................................................................... 19 2.7 Bit Fields ................................................................................................................ 19 2.7.1 Volatile Bit Fields ........................................................................................... 20 2.8 Enumeration Types .................................................................................................... 21 3 Calling Conventions .......................................................................................................... 22 3.1 Call and Return ........................................................................................................ 22 3.1.1 Return Address Computation ............................................................................. 22 3.1.2 Call Instructions ............................................................................................ 22 3.1.3 Return Instruction .......................................................................................... 22 3.1.4 Pipeline Conventions ...................................................................................... 23 3.1.5 Weak Functions ............................................................................................ 23 3.2 Register Conventions .................................................................................................. 23 3.3 Argument Passing ..................................................................................................... 25 3.4 Return Values .......................................................................................................... 25 3.5 Structures or Unions Passed and Returned by Reference ....................................................... 26 3.6 Conventions for Compiler Helper Functions ........................................................................ 26 3.7 Scratch Registers for Inter-Section Calls ........................................................................... 26 3.8 Setting Up DP .......................................................................................................... 26 4 Data Allocation and Addressing .......................................................................................... 27 4.1 Data Sections and Segments ........................................................................................ 27 4.2 Allocation and Addressing of Static Data ........................................................................... 28 4.2.1 Addressing Methods for Static Data ..................................................................... 29 4.2.1.1 Near DP-Relative Addressing ........................................................................ 29 4.2.1.2 Far DP-Relative Addressing .......................................................................... 29 4.2.1.3 Absolute Addressing .................................................................................. 30 2 Table of Contents SPRAB89A–September 2011–Revised March 2014 Submit Documentation Feedback Copyright © 2011–2014, Texas Instruments Incorporated www.ti.com 4.2.1.4 GOT-Indirect Addressing ............................................................................. 30 4.2.1.5 PC-Relative Addressing .............................................................................. 30 4.2.2 Placement Conventions for Static Data ................................................................. 30 4.2.2.1 Abstract Conventions for Placement ................................................................ 30 4.2.2.2 Abstract Conventions for Addressing ............................................................... 31 4.2.2.3 Linker Requirements .................................................................................. 31 4.2.3 Initialization of Static Data ................................................................................ 31 4.3 Automatic Variables ................................................................................................... 32 4.4 Frame Layout ........................................................................................................... 32 4.4.1 Stack Alignment ............................................................................................ 33 4.4.2 Register Save Order ....................................................................................... 34 4.4.2.1 Big-Endian Pair Swapping ............................................................................ 34 4.4.2.2 Examples ............................................................................................... 35 4.4.3 DATA_MEM_BANK ........................................................................................ 36 4.4.4 C64x+ Specific Stack Layouts ............................................................................ 36 4.4.4.1 _ _c6xabi_push_rts Layout ........................................................................... 36 4.4.4.2 Compact Frame Layout ............................................................................... 37 4.5 Heap-Allocated Objects ............................................................................................... 38 5 Code Allocation and Addressing ......................................................................................... 39 5.1 Computing the Address of a Code Label ........................................................................... 39 5.1.1 Absolute Addressing for Code ............................................................................ 39 5.1.2 PC-Relative Addressing ................................................................................... 39 5.1.3 PC-Relative Addressing Within the Same Section .................................................... 39 5.1.4 Short-Offset PC-Relative Addressing (C64x) ........................................................... 40 5.1.5 GOT-Based Addressing for Code ........................................................................ 40 5.2 Branching ............................................................................................................... 40 5.3 Calls ..................................................................................................................... 40 5.3.1 Direct PC-Relative Call .................................................................................... 40 5.3.2 Far Call Trampoline ........................................................................................ 40 5.3.3 Indirect Calls ................................................................................................ 41 5.4 Addressing Compact Instructions .................................................................................... 41 6 Addressing Model for Dynamic Linking ................................................................................ 43 6.1 Terms and Concepts .................................................................................................. 43 6.2 Overview of Dynamic Linking Mechanisms ........................................................................ 44 6.3 DSOs and DLLs 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