RELEASE_NOTES - manifest_repos/llvm_toolchain - Git at Google

 The following are the changes to 3.5.2.5 compared to 3.5.2.1
 1. The 64-bit C library support for ARMv8 without neon or fp is
 available as libc_nofp.a and libc_nofp.so libraries.

 2. New QC Linker for ARM that is capable of replacing GNU linker.

 3. Fix for issues in elftools (elfcopy, archiver).

 4. Fix incorrect dwarf info for a stack variable that compiler knows to be a
 constant.

 5. The builtins library for ARMv7 is now built with AEABI div0 functions that
 are part of the base platform ABI specification.

 The following are the changes to 3.5.2.1 since 3.5 version release
 1. Fix PIC option passing with Android NDK LTO plugin
 2. Add workaround for Cortex-A53 erratum (835769)

 Please see below for more details on the Snapdragon LLVM ARM 3.5 release
 ----------------------------------------------------------------------------
 This is the release of Snapdragon LLVM ARM C/C++ Compiler version 3.5. This is
 a cross compiler built to run on x86 64-bit Ubuntu Linux (version 10.04 and
 later) and Windows platform (Windows 7 32-bit and 64-bit). This Snapdragon LLVM
 ARM Compiler will generate code only for ARM targets and will not generate code
 for any of the other targets supported by llvm.org LLVM.

 The version 3.5 of Snapdragon LLVM ARM Compiler is based off the llvm.org tip
 as of June 20, 2014. Certain patches after this date from the llvm.org tip have
 been cherry-picked into Snapdragon LLVM to improve stability. In other words
 the Snapdragon LLVM 3.5 release is not based off llvm.org 3.5 release branch
 and hence there are some differences between Snapdragon LLVM 3.5 and llvm.org
 3.5 release; one such example is the "#pragma clang loop" feature that is
 available in llvm.org 3.5 release, but not in the Snapdragon LLVM 3.5 release.
 An additional difference from the llvm.org 3.5 release  is that the Snapdragon
 LLVM ARM Compiler includes proprietary features and optimizations that
 are not available in the llvm.org release.

 The Snapdragon LLVM ARM Compiler uses the integrated assembler for assembling
 and relies on GNU tools for linking.


 NOTE: GLIBCXX_3.4.18 or higher is required to run Snapdragon LLVM 3.5 on Ubuntu
 x86 64-bit hosts; this library is typically available as part of Ubuntu
 distribution or GCC-4.8 x86 distributions.

 The complete user guide for this release of the Snapdragon LLVM ARM Compiler
 can be downloaded from Agile by following the link below:

 http://agiledocument.qualcomm.com/AgileDocument/spring/authorize?itemno=80-VB419-96

 Please send all questions about this release to llvm-arm-support@qualcomm.com.

 The following are some of the key features in the 3.5 version compared to the
 3.4 version

 1. Optimizations for ARMv8 64-bit mode: Snapdragon LLVM ARM 3.5 Compiler now
 supports optimized code generation for both AArch32 and AArch64 (64-bit)
 modes. This includes
   - Exploiting newer capabilities of AArch64 ISA such as double-precision
     vectorization
   - Exploiting more GPRs available in AArch64 ISA to speed up performance
   - Auto-vectorizer tuned to exploit AArch64 ISA capabilities
   - Code generation tuning for Cortex-a53 cores (we expect tuned code
     generation for Cortex-a57 in our next release)

 2. Sanitizers: This release introduces support for Undefined Behavior
 sanitizer, a new security checker that checks usage of semantics that
 result in undefined behavior such as unsigned integer overflow.

 3. Significantly improved Link time optimizer (LTO): This release includes new
 LTO flags that allow users to optimize performance or size. The LTO compiler
 flow has also been updated to use the Gold linker plugin. At the time of
 release, Gold does not support ARMv8, so LTO is only available for ARMv7 targets.

 4. A mature Auto-parallelizer runtime is available for 32-bit ARMv7
 targets and an initial version of the Auto-parallelizer and runtime for
 the 64-bit Linux environment (Android support for 64-bit
 Auto-parallelizer will be available in the next release).


 Basic Usage & Examples:

 clang and clang++ are the C and C++ drivers respectively of Snapdragon
 LLVM ARM Compiler. They require users to specify the assembler and linker
 explicitly.

 For Windows:

 In order to use the drivers you need to specify a Windows version of the GCC
 cross toolchain as the sysroot.

 To invoke the compiler from a Windows command prompt:

 set PATH=<path-to-compiler-bin>;<path-to-sysroot-bin>;%PATH%

 clang.exe -mfloat-abi=softfp --sysroot=<path/to/sysroot> -ccc-gcc-name
 arm-none-linux-gnueabi-g++ foo.c

 where arm-none-linux-gnueabi-g++ is the name of the compiler in <sysroot>/bin

 NOTE:
 Microsoft Visual C++ 2013 x86 Redistributable is required in order to use the
 Windows version of Snapdragon LLVM ARM 3.5. If the invocation of clang.exe
 results in a "Missing DLL" message popup on your windows system, you are likely
 missing the Redistributable dlls. Please install the 32-bit version of MSVC++
 redistributables if they are reported missing.  If your system does not already
 have the required dll,  you can download and install it from the following
 link:

 https://www.microsoft.com/en-us/download/details.aspx?id=40784

 Click "Download" and select "vcredist_x86.exe" to install the 32-bit version of
 MSVC++ redistributable required for Snapdragon LLVM ARM 3.5

 NOTE:
 The Gold linker plugin is not available for Windows platform. Hence the LTO feature
 cannot be used with the Windows version of Snapdragon LLVM ARM 3.5 compiler.

 For Linux:

 Note that the Linux version of clang is built with support for using GCC
 sysroot at /pkg/qct/software/llvm/build_tools/gcc-4.6.1-cs/arm-2011.09 by
 default. Users can use a different sysroot (such as GCC-4.9 sysroot) by using
 the --sysroot option as described in section 3.7 of the Snapdragon ARM LLVM
 Compiler guide.

 Examples of Linux driver usage:
 clang -march=armv7-a -mfloat-abi=softfp -mfpu=neon -O3 -o foo foo.c
 clang++ -mcpu=krait2 -mfloat-abi=softfp -mfpu=neon -Os -mthumb -o bar bar.cpp
 clang++ -mcpu=krait2 -mfpu=neon -mfloat-abi=softfp -mfpu=neon
 --sysroot=</path/to/another-gcc-sysroot> -Ofast -c test.cpp

 For Android:

 If you would like to use Snapdragon LLVM ARM Compiler to target an Android platform
 for building Android components, please contact llvm-arm-support@qualcomm.com

 For generating executables that can be executed on ARM Linux and Android
 environment, we recommend using -static linker flag to enable generation of
 static executables which do not have dependence on runtime OS libraries.

 Options:

 To find out the most common options, please pass -help flag to the clang
 driver. This will report the Snapdragon LLVM ARM specific options and
 general ARM options first, before listing target independent options
 available in Snapdragon LLVM ARM Compiler.

 Compiler options for best performance:

 For 64-bit applications, we recommend using "-Ofast -mcpu=cortex-a53" options
 for best performance on all 64-bit cores, including Cortex-a57, since our
 evaluation on Cortex-a57 has shown that -mcpu=cortex-a53 option performs
 better than the -mcpu=cortex-a57.

 For 32-bit, we recommend using the "-Ofast -mcpu=krait2" options for best
 performance of your application on Krait cores. For non-Krait 32-bit cores, we
 recommend using the "-Ofast" option. If you would like to avoid the generation
 of Krait specific instructions (hardware divide, fused-mac) to enable running
 on a variety of ARMv7 cores, but still optimize for best performance on Krait
 cores, we recommend the "-Ofast -mtune=krait2 -march=armv7-a" option list.

 The -Ofast option enables several high performance optimizations such as
 Auto-vectorizer. Please refer to section 3.4.18 of the Snapdragon LLVM ARM
 Compiler guide for more details.

 Compiler options for smallest code-size:

 We recommending using the "-Osize -mthumb" options to generate the most compact
 code with the Snapdragon LLVM 3.5 compiler. Please refer to section 3.4.18 for
 more details on the -Osize optimization level

 Compiling for AArch64:

 To compile for AArch64 (ARMv8 64-bit mode), please pass

 -target aarch64-linux-gnu

 option to clang.

 Compiling for AArch32:

 To compile for AArch32 please pass

 -target armv8-linux-gnueabi

 option to clang. Note that even though AArch32 ISA is fully backward compatible
 with ARMv7 ISA, there are new instructions in AArch32 ISA compared to ARMv7
 ISA. This means that AArch32 executables cannot be executed on ARMv7 cores such
 as Krait.

 Please refer to section 3.6 of the Snapdragon LLVM ARM Compiler user guide to
 learn about various optimizations flags.

 LLVM's Support for GCC command line options:

 Most of the commonly used GCC options are supported by LLVM as well. A detailed
 list of options supported is listed in chapter 3 of the Snapdragon LLVM ARM
 Compiler user guide.

 Use and Distribution:

 This release is strictly for internal distribution and should not be
 distributed outside of Qualcomm. An external release is available on
 QDevNet for customer access.

 Contacts & Bug Reporting
 llvm-arm-support@qualcomm.com
	The following are the changes to 3.5.2.5 compared to 3.5.2.1
	1. The 64-bit C library support for ARMv8 without neon or fp is
	available as libc_nofp.a and libc_nofp.so libraries.

	2. New QC Linker for ARM that is capable of replacing GNU linker.

	3. Fix for issues in elftools (elfcopy, archiver).

	4. Fix incorrect dwarf info for a stack variable that compiler knows to be a
	constant.

	5. The builtins library for ARMv7 is now built with AEABI div0 functions that
	are part of the base platform ABI specification.

	The following are the changes to 3.5.2.1 since 3.5 version release
	1. Fix PIC option passing with Android NDK LTO plugin
	2. Add workaround for Cortex-A53 erratum (835769)

	Please see below for more details on the Snapdragon LLVM ARM 3.5 release
	----------------------------------------------------------------------------
	This is the release of Snapdragon LLVM ARM C/C++ Compiler version 3.5. This is
	a cross compiler built to run on x86 64-bit Ubuntu Linux (version 10.04 and
	later) and Windows platform (Windows 7 32-bit and 64-bit). This Snapdragon LLVM
	ARM Compiler will generate code only for ARM targets and will not generate code
	for any of the other targets supported by llvm.org LLVM.

	The version 3.5 of Snapdragon LLVM ARM Compiler is based off the llvm.org tip
	as of June 20, 2014. Certain patches after this date from the llvm.org tip have
	been cherry-picked into Snapdragon LLVM to improve stability. In other words
	the Snapdragon LLVM 3.5 release is not based off llvm.org 3.5 release branch
	and hence there are some differences between Snapdragon LLVM 3.5 and llvm.org
	3.5 release; one such example is the "#pragma clang loop" feature that is
	available in llvm.org 3.5 release, but not in the Snapdragon LLVM 3.5 release.
	An additional difference from the llvm.org 3.5 release is that the Snapdragon
	LLVM ARM Compiler includes proprietary features and optimizations that
	are not available in the llvm.org release.

	The Snapdragon LLVM ARM Compiler uses the integrated assembler for assembling
	and relies on GNU tools for linking.


	NOTE: GLIBCXX_3.4.18 or higher is required to run Snapdragon LLVM 3.5 on Ubuntu
	x86 64-bit hosts; this library is typically available as part of Ubuntu
	distribution or GCC-4.8 x86 distributions.

	The complete user guide for this release of the Snapdragon LLVM ARM Compiler
	can be downloaded from Agile by following the link below:

	http://agiledocument.qualcomm.com/AgileDocument/spring/authorize?itemno=80-VB419-96

	Please send all questions about this release to llvm-arm-support@qualcomm.com.

	The following are some of the key features in the 3.5 version compared to the
	3.4 version

	1. Optimizations for ARMv8 64-bit mode: Snapdragon LLVM ARM 3.5 Compiler now
	supports optimized code generation for both AArch32 and AArch64 (64-bit)
	modes. This includes
	- Exploiting newer capabilities of AArch64 ISA such as double-precision
	vectorization
	- Exploiting more GPRs available in AArch64 ISA to speed up performance
	- Auto-vectorizer tuned to exploit AArch64 ISA capabilities
	- Code generation tuning for Cortex-a53 cores (we expect tuned code
	generation for Cortex-a57 in our next release)

	2. Sanitizers: This release introduces support for Undefined Behavior
	sanitizer, a new security checker that checks usage of semantics that
	result in undefined behavior such as unsigned integer overflow.

	3. Significantly improved Link time optimizer (LTO): This release includes new
	LTO flags that allow users to optimize performance or size. The LTO compiler
	flow has also been updated to use the Gold linker plugin. At the time of
	release, Gold does not support ARMv8, so LTO is only available for ARMv7 targets.

	4. A mature Auto-parallelizer runtime is available for 32-bit ARMv7
	targets and an initial version of the Auto-parallelizer and runtime for
	the 64-bit Linux environment (Android support for 64-bit
	Auto-parallelizer will be available in the next release).


	Basic Usage & Examples:

	clang and clang++ are the C and C++ drivers respectively of Snapdragon
	LLVM ARM Compiler. They require users to specify the assembler and linker
	explicitly.

	For Windows:

	In order to use the drivers you need to specify a Windows version of the GCC
	cross toolchain as the sysroot.

	To invoke the compiler from a Windows command prompt:

	set PATH=<path-to-compiler-bin>;<path-to-sysroot-bin>;%PATH%

	clang.exe -mfloat-abi=softfp --sysroot=<path/to/sysroot> -ccc-gcc-name
	arm-none-linux-gnueabi-g++ foo.c

	where arm-none-linux-gnueabi-g++ is the name of the compiler in <sysroot>/bin

	NOTE:
	Microsoft Visual C++ 2013 x86 Redistributable is required in order to use the
	Windows version of Snapdragon LLVM ARM 3.5. If the invocation of clang.exe
	results in a "Missing DLL" message popup on your windows system, you are likely
	missing the Redistributable dlls. Please install the 32-bit version of MSVC++
	redistributables if they are reported missing. If your system does not already
	have the required dll, you can download and install it from the following
	link:

	https://www.microsoft.com/en-us/download/details.aspx?id=40784

	Click "Download" and select "vcredist_x86.exe" to install the 32-bit version of
	MSVC++ redistributable required for Snapdragon LLVM ARM 3.5

	NOTE:
	The Gold linker plugin is not available for Windows platform. Hence the LTO feature
	cannot be used with the Windows version of Snapdragon LLVM ARM 3.5 compiler.

	For Linux:

	Note that the Linux version of clang is built with support for using GCC
	sysroot at /pkg/qct/software/llvm/build_tools/gcc-4.6.1-cs/arm-2011.09 by
	default. Users can use a different sysroot (such as GCC-4.9 sysroot) by using
	the --sysroot option as described in section 3.7 of the Snapdragon ARM LLVM
	Compiler guide.

	Examples of Linux driver usage:
	clang -march=armv7-a -mfloat-abi=softfp -mfpu=neon -O3 -o foo foo.c
	clang++ -mcpu=krait2 -mfloat-abi=softfp -mfpu=neon -Os -mthumb -o bar bar.cpp
	clang++ -mcpu=krait2 -mfpu=neon -mfloat-abi=softfp -mfpu=neon
	--sysroot=</path/to/another-gcc-sysroot> -Ofast -c test.cpp

	For Android:

	If you would like to use Snapdragon LLVM ARM Compiler to target an Android platform
	for building Android components, please contact llvm-arm-support@qualcomm.com

	For generating executables that can be executed on ARM Linux and Android
	environment, we recommend using -static linker flag to enable generation of
	static executables which do not have dependence on runtime OS libraries.

	Options:

	To find out the most common options, please pass -help flag to the clang
	driver. This will report the Snapdragon LLVM ARM specific options and
	general ARM options first, before listing target independent options
	available in Snapdragon LLVM ARM Compiler.

	Compiler options for best performance:

	For 64-bit applications, we recommend using "-Ofast -mcpu=cortex-a53" options
	for best performance on all 64-bit cores, including Cortex-a57, since our
	evaluation on Cortex-a57 has shown that -mcpu=cortex-a53 option performs
	better than the -mcpu=cortex-a57.

	For 32-bit, we recommend using the "-Ofast -mcpu=krait2" options for best
	performance of your application on Krait cores. For non-Krait 32-bit cores, we
	recommend using the "-Ofast" option. If you would like to avoid the generation
	of Krait specific instructions (hardware divide, fused-mac) to enable running
	on a variety of ARMv7 cores, but still optimize for best performance on Krait
	cores, we recommend the "-Ofast -mtune=krait2 -march=armv7-a" option list.

	The -Ofast option enables several high performance optimizations such as
	Auto-vectorizer. Please refer to section 3.4.18 of the Snapdragon LLVM ARM
	Compiler guide for more details.

	Compiler options for smallest code-size:

	We recommending using the "-Osize -mthumb" options to generate the most compact
	code with the Snapdragon LLVM 3.5 compiler. Please refer to section 3.4.18 for
	more details on the -Osize optimization level

	Compiling for AArch64:

	To compile for AArch64 (ARMv8 64-bit mode), please pass

	-target aarch64-linux-gnu

	option to clang.

	Compiling for AArch32:

	To compile for AArch32 please pass

	-target armv8-linux-gnueabi

	option to clang. Note that even though AArch32 ISA is fully backward compatible
	with ARMv7 ISA, there are new instructions in AArch32 ISA compared to ARMv7
	ISA. This means that AArch32 executables cannot be executed on ARMv7 cores such
	as Krait.

	Please refer to section 3.6 of the Snapdragon LLVM ARM Compiler user guide to
	learn about various optimizations flags.

	LLVM's Support for GCC command line options:

	Most of the commonly used GCC options are supported by LLVM as well. A detailed
	list of options supported is listed in chapter 3 of the Snapdragon LLVM ARM
	Compiler user guide.

	Use and Distribution:

	This release is strictly for internal distribution and should not be
	distributed outside of Qualcomm. An external release is available on
	QDevNet for customer access.

	Contacts & Bug Reporting
	llvm-arm-support@qualcomm.com