NVIDIA® Nsight™ Development Platform, Visual Studio Edition 3.0 User Guide
PTX is a low-level parallel-thread execution virtual machine and instruction set architecture (ISA). PTX exposes the GPU as a parallel computing device.
In addition, PTX provides a stable programming model and instruction set for general purpose parallel programming, and is designed to be efficient on NVIDIA GPUs. High-level language compilers for languages such as CUDA and C/C++ generate PTX instructions, which are optimized for and translated to native target-architecture instructions.
SASS is the low-level assembly language that compiles to binary microcode, which executes natively on NVIDIA GPU hardware.
With NVIDIA Nsight 3.0, PTX and SASS assembly debugging is now available. To utilize this feature, use the following tutorial.
Currently, this only works with CUDA applications that have debug symbolics (i.e., that are built with –G0).
In addition, this displays only one CUDA function for the current stopped kernel. The user cannot scroll to other CUDA kernels in the module.
This can only work when stopped in a CUDA kernel via a breakpoint. There is no static or offline disassembly in the Visual Studio disassembly view.
Note that the Show Symbols option is currently not supported.
The number in brackets  in the Visual Studio Disassembly View is the PTX line number.
With the CUDA Debugger PTX and SASS assembly debugging feature, address breakpoints are supported. Standard Visual Studio controls for adding and removing breakpoints can be seen in the breakpoint column of the disassembly.
A few items to note with address breakpoints:
When using run control with the CUDA Debugger PTX and SASS assembly debugging, stepping in / out / over all work normally as expected. This follows the Visual Studio Source, Statement, and Instruction control. Stepping in the last line of a kernel will continue the program.
When stepping instructions (which is the default for disassembly) and SASS is showing, the CUDA Debugger will always step at the SASS level.
Note that there is no control for stepping PTX when SASS is showing.
Additional information on PTX can be found in the CUDA 4.0 documentation:
<NVIDIA GPU Computing Toolkit installation path>\CUDA\v4.0\doc\
NVIDIA® Nsight™ Development Platform, Visual Studio Edition User Guide Rev. 3.0.130507 ©2009-2013. NVIDIA Corporation. All Rights Reserved.
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