Note that all of this is predicated on High Level Synthesis (HLS) becoming real, after many years of industry over-promises and under-deliveries.
A jaded RTL engineer may fairly ask, "what's different this time?" I'm convinced it's two things:
1. These chips have scaled to the point where the toolflow isn't just annoying, it's crippling. (I say that as an RTL designer who likes Vivado, believe it or not.) Making effective use of the largest FPGAs in traditional FPGA applications is difficult enough. Plus, the marginal cost of baking e.g. ARM cores onto an FPGA is now so low that these parts are quickly becoming heterogeneous SoCs and it requires extensive cross-domain knowledge to get a modern design off the ground. More importantly, though, Xilinx is trying to expand FPGAs beyond traditional FPGA markets, and it can't do so without expanding the pool of available talent to program them. Finally, new FPGA applications (e.g. AI) come with their own technical arcana and finding FPGA designers who are proficient in all of these domains is only growing harder. It is necessary for the tools to help, and Xilinx is amply incentivized to pour money into the R&D programs necessary, even if the new tools are simply bundled alongside the old ones.
2. This may be a surprise, but LLVM. Doing HLS correctly is a forced march through every conceivable corner of compiler, language, and RTL design, and to date, that's been much too difficult for EDA companies. I believe that LLVM as an accessible compiler workshop has been instrumental to Xilinx's success to date.
I hope Xilinx does genuinely open-source some of the pieces. (Not the synthesis flow, in this case, but all the stuff built on top of it.) The open-source EDA community is small but motivated and talented, but it's crippled by balkanization caused by the commercial EDA market. This might be an interesting shot in the arm.
HLS is real. I've talked with dozens of teams who have successfully used HLS tools such as Mentor's Catapult, Xilinx's Vivado HLS, and Cadence's Stratus for a wide range of ASIC and FPGA projects. They claim they saw compelling benefits in project schedules, architectural flexibility, and overall performance. However, HLS is still (IMHO) a "power tool" for competent digital designers, not a tool that enables a software designer to create hardware. There is too much hardware-specific expertise required to create good HLS-able code and to do the tradeoffs like pipelining, unrolling, memory architecture, etc etc etc.
I'm curious: why is FPGA tooling so poor? I used a Spartan-3 over a decade ago for a simple project, and as cursory look it doesn't seem like things have changed much despite the devices becoming significantly more diverse and complicated.
It's not quite fair to say the tooling is flat-out awful. Vivado is much better than ISE. The place/route algorithms matured (analytical placement rather than simulated annealing), and the software it's wrapped in grew up (it's now tcl-driven and much more script- and revision-control-friendly.) Vivado was a heroic effort and Xilinx deserves credit for taking software seriously, and getting so much of it right. If you don't believe me, try hiring an FPGA engineer today to work on an ISE project. You'll get an earful.
That said, a solid, open-source, mixed-language simulator with good SystemVerilog and VHDL-2008 support would change my life. Bonus points if I can embed it in C/C++ code a la Verilator. And, while I'm asking, can it simulate encrypted IP too?
This is one of the places where HLS may sideswipe the traditional RTL market: if you can effectively develop FPGA designs in C++, the entire approach to development/testing/integration changes completely. It may sound like a detail, but it touches every single pain point associated with a complex FPGA design.
I'm using Vivado right now. Things I hate about it:
- It's sluggish. The underlying algorithms may be fast (they handle huge designs), but even with an empty design it's sluggish. I'm not sure if this is from the Java or the TCL. On the other handle Altera/Intel Quartus is faster.. (it also uses Java and TCL..)
- I hate TCL. This whole concept of an integrated extension language in a massive tool is terrible. It's the standard way in the EDA world, but it's not good at all. I prefer simpler tools tied together with Makefiles..
- I hate the schematic-like block designs. I just want a single Verilog file that represents the design, no XML. The block designs are difficult to integrate with git.
- I hate projects. They are difficult to integrate with git: you have to export project tcl, then regenerate the project from this checked in file. It's aweful and breaks when the design gets complicated.
- I'm using Zynq Ultrascale+ and I hate eclipse. The EDK is eclipse-based. I just want a command line tool to generate a project from the hardware description so that I never have to open the Eclipse. True, once your hardware is stabilized, you can avoid it (it does generate a Makefile). I've not tried Altera's SoCs, so not sure if better.
That being said, Xilinx did a good job with the BSP software and the Linux support. At least it's better than what we see on some embedded processors (Nvidia, ugh..)
Also I recently ported a design from Zynq (32-bit) to Zynq Ultrascale+ (64-bit). Not bad at all.
These are all fair criticisms. Block designs, XML files for project and IP management, and auto-generated .tcl are all bad things. Eclipse sucks.
I understand why vendors ship tools with all of these things. I think (hope?) they're slowly un-bundling more and more of the toolflow so you can avoid them if you want.
FWIW the ISE tooling was all command line driven and could be orchestrated from a makefile and controlled by a VCS. You'd lose some of the graphical convenience to monitor issues and reporting but it can be done.
HLS's problem is how to deal with assumptions about memory access and parallelism. You invariably end up coding to the tool to accommodate the limitations of C in this domain.
Mostly because it's (almost) all proprietary. None of the companies are investing in a truly usable solution. It speaks volumes that a handful of developers working for free where able to create a vastly better experience with yosys and friends.
Most of the development is for the military. It gets farmed to contractors who use all the same stuff you have access to, just typically several years out of date.
The ability to fully enumerate and simulate every part of the design gives them a huge hardon even though stuff frequently passes simulation and fails on the silicon. It's very common to see FPGAs in nuclear, military RF, and aerospace applications.
There are no separate tools for military use. And, the mil/aero versions of the chips are usually a generation or two behind because of the extra work to make them high-reliability, produce the required documentation, etc.
A jaded RTL engineer may fairly ask, "what's different this time?" I'm convinced it's two things:
1. These chips have scaled to the point where the toolflow isn't just annoying, it's crippling. (I say that as an RTL designer who likes Vivado, believe it or not.) Making effective use of the largest FPGAs in traditional FPGA applications is difficult enough. Plus, the marginal cost of baking e.g. ARM cores onto an FPGA is now so low that these parts are quickly becoming heterogeneous SoCs and it requires extensive cross-domain knowledge to get a modern design off the ground. More importantly, though, Xilinx is trying to expand FPGAs beyond traditional FPGA markets, and it can't do so without expanding the pool of available talent to program them. Finally, new FPGA applications (e.g. AI) come with their own technical arcana and finding FPGA designers who are proficient in all of these domains is only growing harder. It is necessary for the tools to help, and Xilinx is amply incentivized to pour money into the R&D programs necessary, even if the new tools are simply bundled alongside the old ones.
2. This may be a surprise, but LLVM. Doing HLS correctly is a forced march through every conceivable corner of compiler, language, and RTL design, and to date, that's been much too difficult for EDA companies. I believe that LLVM as an accessible compiler workshop has been instrumental to Xilinx's success to date.
I hope Xilinx does genuinely open-source some of the pieces. (Not the synthesis flow, in this case, but all the stuff built on top of it.) The open-source EDA community is small but motivated and talented, but it's crippled by balkanization caused by the commercial EDA market. This might be an interesting shot in the arm.