Introduction

Gallium LLVMpipe Driver

+ +

Introduction

The Gallium llvmpipe driver is a software rasterizer that uses LLVM to do runtime code generation. Shaders, point/line/triangle rasterization and vertex processing are -implemented with LLVM IR which is translated to x86 or x86-64 machine +implemented with LLVM IR which is translated to x86, x86-64, or ppc64le machine code. Also, the driver is multithreaded to take advantage of multiple CPU cores (up to 8 at this time). @@ -28,30 +30,36 @@ It's the fastest software rasterizer for Mesa.

Requirements

-
An x86 or amd64 processor; 64-bit mode recommended.

+ For x86 or amd64 processors, 64-bit mode is recommended. Support for SSE2 is strongly encouraged. Support for SSE3 and SSE4.1 will yield the most efficient code. The fewer features the CPU has the more - likely is that you run into underperforming, buggy, or incomplete code. + likely it is that you will run into underperforming, buggy, or incomplete code. +
+
+ For ppc64le processors, use of the Altivec feature (the Vector + Facility) is recommended if supported; use of the VSX feature (the + Vector-Scalar Facility) is recommended if supported AND Mesa is + built with LLVM version 4.0 or later.

- See /proc/cpuinfo to know what your CPU supports. + See /proc/cpuinfo to know what your CPU supports.
-
LLVM: version 3.4 recommended; 3.3 or later required.
+
Unless otherwise stated, LLVM version 3.4 is recommended; 3.3 or later is required.

For Linux, on a recent Debian based distribution do:
```
-     aptitude install llvm-dev
+aptitude install llvm-dev
 
```
- If you want development snaptshot builds of LLVM for Debian and derived + If you want development snapshot builds of LLVM for Debian and derived distributions like Ubuntu, you can use the APT repository at apt.llvm.org, which are maintained by Debian's LLVM maintainer. @@ -60,13 +68,14 @@ It's the fastest software rasterizer for Mesa. For a RPM-based distribution do:
```
-     yum install llvm-devel
+yum install llvm-devel
 
```
For Windows you will need to build LLVM from source with MSVC or MINGW - (either natively or through cross compilers) and CMake, and set the LLVM - environment variable to the directory you installed it to. + (either natively or through cross compilers) and CMake, and set the + LLVM environment variable to the directory you installed + it to. LLVM will be statically linked, so when building on MSVC it needs to be built with a matching CRT as Mesa, and you'll need to pass @@ -95,8 +104,8 @@ It's the fastest software rasterizer for Mesa.
- You can build only the x86 target by passing -DLLVM_TARGETS_TO_BUILD=X86 - to cmake. + You can build only the x86 target by passing + -DLLVM_TARGETS_TO_BUILD=X86 to cmake.

Building

To build everything on Linux invoke scons as:

-  scons build=debug libgl-xlib
+scons build=debug libgl-xlib

-Alternatively, you can build it with autoconf/make with: +Alternatively, you can build it with meson with:

-  ./configure --enable-glx=gallium-xlib --with-gallium-drivers=swrast --disable-dri --disable-gbm --disable-egl
-  make
+mkdir build
+cd build
+meson -D glx=gallium-xlib -D gallium-drivers=swrast
+ninja

but the rest of these instructions assume that scons is used. @@ -125,31 +136,34 @@ but the rest of these instructions assume that scons is used. For Windows the procedure is similar except the target:

-  scons platform=windows build=debug libgl-gdi
+scons platform=windows build=debug libgl-gdi

Using

Linux

On Linux, building will create a drop-in alternative for libGL.so into

On Linux, building will create a drop-in alternative for +libGL.so into

-  build/foo/gallium/targets/libgl-xlib/libGL.so
+build/foo/gallium/targets/libgl-xlib/libGL.so

-  lib/gallium/libGL.so
+lib/gallium/libGL.so

To use it set the LD_LIBRARY_PATH environment variable accordingly.

To use it set the LD_LIBRARY_PATH environment variable +accordingly.

For performance evaluation pass build=release to scons, and use the corresponding -lib directory without the "-debug" suffix.

For performance evaluation pass build=release to scons, +and use the corresponding lib directory without the -debug +suffix.

Windows

On Windows, building will create @@ -167,7 +181,9 @@ any OpenGL drivers):

copy build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll to C:\Windows\SysWOW64\mesadrv.dll
copy build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll + to C:\Windows\SysWOW64\mesadrv.dll +

load this registry settings:

REGEDIT4
 
@@ -184,13 +200,13 @@ any OpenGL drivers):

Profiling

To profile llvmpipe you should build as

-  scons build=profile <same-as-before>
+scons build=profile <same-as-before>

@@ -198,73 +214,76 @@ This will ensure that frame pointers are used both in C and JIT functions, and that no tail call optimizations are done by gcc.

Linux perf integration

On Linux, it is possible to have symbol resolution of JIT code with Linux perf:

-	perf record -g /my/application
-	perf report
+perf record -g /my/application
+perf report

-When run inside Linux perf, llvmpipe will create a /tmp/perf-XXXXX.map file with -symbol address table. It also dumps assembly code to /tmp/perf-XXXXX.map.asm, -which can be used by the bin/perf-annotate-jit.py script to produce disassembly of -the generated code annotated with the samples. +When run inside Linux perf, llvmpipe will create a +/tmp/perf-XXXXX.map file with symbol address table. It also +dumps assembly code to /tmp/perf-XXXXX.map.asm, which can be +used by the bin/perf-annotate-jit.py script to produce +disassembly of the generated code annotated with the samples.

You can obtain a call graph via Gprof2Dot.

Unit testing

Building will also create several unit tests in -build/linux-???-debug/gallium/drivers/llvmpipe: +build/linux-???-debug/gallium/drivers/llvmpipe:

lp_test_blend: blending -
lp_test_conv: SIMD vector conversion -
lp_test_format: pixel unpacking/packing +
lp_test_blend: blending +
lp_test_conv: SIMD vector conversion +
lp_test_format: pixel unpacking/packing

-Some of this tests can output results and benchmarks to a tab-separated-file -for posterior analysis, e.g.: +Some of these tests can output results and benchmarks to a tab-separated file +for later analysis, e.g.:

-  build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
+build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv

Development Notes

- When looking to this code by the first time start in lp_state_fs.c, and - then skim through the lp_bld_* functions called in there, and the comments - at the top of the lp_bld_*.c functions. + When looking at this code for the first time, start in lp_state_fs.c, and + then skim through the lp_bld_* functions called there, and + the comments at the top of the lp_bld_*.c functions.
The driver-independent parts of the LLVM / Gallium code are found in - src/gallium/auxiliary/gallivm/. The filenames and function prefixes - need to be renamed from "lp_bld_" to something else though. + src/gallium/auxiliary/gallivm/. The filenames and function + prefixes need to be renamed from lp_bld_ to something else + though.
We use LLVM-C bindings for now. They are not documented, but follow the C++ interfaces very closely, and appear to be complete enough for code generation. See - this stand-alone example. See the llvm-c/Core.h file for reference. + this stand-alone example. See the llvm-c/Core.h file for + reference.

The Mesa 3D Graphics Library

Introduction

Gallium LLVMpipe Driver

Introduction

Requirements

Requirements

Building

Building

Using

Using

Linux

Linux

Windows

Windows

Profiling

Profiling

Linux perf integration

Linux perf integration

Unit testing

Unit testing

Development Notes

Development Notes

Recommended Reading

Recommended Reading