Hello Steven,

On 3 August 2016 at 08:48, Shi, Steven <steven.shi@...> wrote:

This adds support for LLVM 3.8.x in LTO mode for IA32 and X64.
CLANG38 enable LLVM Link Time Optimization (LTO) and code size
optimization flag (-Oz) by default for aggressive code size
improvement. CLANG38 X64 code is small code model + PIE.

CLANG LTO needs PIE in link flags to generate PIE code correctly,
otherwise the PIE is not really enabled. (e.g. OvmfPkgX64 will
hang in 64bits SEC at high address because of small model code
displacement overflow).

This is probably caused by the same issue I am addressing with the
series I sent out yesterday, to pass the CC flags to the DLINK
command.

The reason is that code is generated by the link pass, so it needs to
see the same -fpie -mcmodel=small options that we passed to the
compiler as wel.

Could you check whether replacing '-Wl,-pie' with -fpie does the trick
as well? As I mentioned before, creating a PIE executable at link time
is not the same as generatic position independent code at compile time
(whether it is via $(CC) or via $(DLINK)). The PIE executable will
contain a .rela section that partially overlaps with other absolute
relocations, so it is best to avoid it.

Some more comments below

Test pass platforms: OVMF (OvmfPkgIa32.dsc, OvmfPkgX64.dsc and
OvmfPkgIa32X64.dsc).
Test compiler and linker version: LLVM 3.8, GNU ld 2.26.

Example steps to use the CLANG38 tool chain to build OVMF platform:
1. Download and extract the llvm 3.8.0 Pre-Built Binaries from
http://www.llvm.org/releases/ (e.g. http://www.llvm.org/releases/
3.8.0/clang+llvm-3.8.0-x86_64-linux-gnu-ubuntu-16.04.tar.xz and
extract it as ~/clang38).
2. Copy LLVMgold.so from https://github.com/shijunjing/edk2/blob/
llvm/BaseTools/Bin/LLVMgold.so to above clang lib folder (e.g.
~/clang38/lib/LLVMgold.so)
3. Install new version linker with plugin support (e.g. ld 2.26 in
GNU Binutils 2.26 or Ubuntu16.04)
$ cd edk2
$ git checkout llvm
$ export CLANG38_BIN=path/to/your/clang38/
(e.g. export CLANG38_BIN=~/clang38/bin/)
$ source edksetup.sh
$ make -C BaseTools/Source/C
$ build -t CLANG38 -a X64 -p OvmfPkg/OvmfPkgX64.dsc -n 5 -b DEBUG
-DDEBUG_ON_SERIAL_PORT
$ cd edk2/Build/OvmfX64/DEBUG_CLANG38/FV
$ qemu-system-x86_64.exe -bios OVMF.fd -serial file:serial.log -m 4096
-hda fat:.

If you want, you can build and install GNU Binutils 2.26 as below steps
in Ubuntu:
Download binutils-2.26 source code from http://ftp.gnu.org/gnu/binutils/
and extract it to ~/binutils-2.26
$sudo apt-get install bison
$sudo apt-get install flex
Install other necessary binutils build tools if missing
$ mkdir build
$ cd build
$ ../binutils-2.26/configure --enable-gold --enable-plugins
--disable-werror --prefix=/usr
$ make -j 5
$ sudo make install

If you want, you can build LLVMgold.so as below steps
Download llvm-3.8.0 source code from http://www.llvm.org/releases/
3.8.0/llvm-3.8.0.src.tar.xz and extract it to ~/llvm-3.8.0.src
Download clang3.8.0 source code from http://www.llvm.org/releases/
3.8.0/cfe-3.8.0.src.tar.xz and extract it to ~/llvm-3.8.0.src/tools/clang
Refer http://clang.llvm.org/get_started.html to Install other necessary
clang build tools if missing
$ mkdir llvm38build
$ cd llvm38build
If your GNU Binutils 2.26 is in /home/jshi19/binutils-2.26,
$ cmake ../llvm-3.8.0.src -G "Unix Makefiles" -DCMAKE_BUILD_TYPE="Release"
-DLLVM_TARGETS_TO_BUILD="X86" -DCMAKE_VERBOSE_MAKEFILE=ON
-DCMAKE_CXX_COMPILER="/usr/bin/g++" -DCMAKE_C_COMPILER="/usr/bin/gcc"
-DLLVM_BINUTILS_INCDIR=/home/jshi19/binutils-2.26/include
$ make -j 5 LLVMgold The LLVMgold.so is in ~/llvm38build/lib/LLVMgold.so

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Steven Shi <steven.shi@...>
---
BaseTools/Conf/tools_def.template | 81 +++++++++++++++++++++++++++++++++++++++
1 file changed, 81 insertions(+)
mode change 100644 => 100755 BaseTools/Conf/tools_def.template

diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
old mode 100644
new mode 100755
index fd9eccb..6d964f1
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -5428,6 +5428,87 @@ RELEASE_CLANG35_AARCH64_CC_FLAGS = DEF(CLANG35_AARCH64_CC_FLAGS) $(ARCHCC_FLAGS)

####################################################################################
#
+# Clang 3.8 - This configuration is used to compile under Linux to produce
+# PE/COFF binaries using LLVM/Clang 3.8 with Link Time Optimization enabled
+#
+####################################################################################
+*_CLANG38_*_*_FAMILY = GCC
+*_CLANG38_*_MAKE_PATH = DEF(GCC5_IA32_PREFIX)make
+*_CLANG38_*_*_DLL = ENV(CLANG38_DLL)
+*_CLANG38_*_ASL_PATH = DEF(UNIX_IASL_BIN)
+
+*_CLANG38_*_APP_FLAGS =
+*_CLANG38_*_ASL_FLAGS = DEF(IASL_FLAGS)
+*_CLANG38_*_ASL_OUTFLAGS = DEF(IASL_OUTFLAGS)
+
+DEFINE CLANG38_IA32_PREFIX = ENV(CLANG38_BIN)
+DEFINE CLANG38_X64_PREFIX = ENV(CLANG38_BIN)
+
+DEFINE CLANG38_IA32_TARGET = -target i686-pc-linux-gnu
+DEFINE CLANG38_X64_TARGET = -target x86_64-pc-linux-gnu
+
+DEFINE CLANG38_ALL_CC_FLAGS = DEF(GCC44_ALL_CC_FLAGS) -Wno-empty-body -fno-stack-protector -fno-builtin -mms-bitfields -Wno-address -Wno-shift-negative-value -Wno-parentheses-equality -Wno-unknown-pragmas -Wno-tautological-constant-out-of-range-compare -Wno-incompatible-library-redeclaration -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -msoft-float -mno-implicit-float -ftrap-function=undefined_behavior_has_been_optimized_away_by_clang -funsigned-char -fno-ms-extensions -Wno-null-dereference -Wno-tautological-compare
+
+###########################
+# CLANG38 IA32 definitions
+###########################
+*_CLANG38_IA32_OBJCOPY_PATH = DEF(GCC5_IA32_PREFIX)objcopy

Why are you using the GCC5 prefix here? A clang user may not set GCC5_BIN

+*_CLANG38_IA32_CC_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_SLINK_PATH = DEF(CLANG38_IA32_PREFIX)llvm-ar
+*_CLANG38_IA32_DLINK_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_ASLDLINK_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_ASM_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_PP_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_VFRPP_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_ASLCC_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_ASLPP_PATH = DEF(CLANG38_IA32_PREFIX)clang
+*_CLANG38_IA32_RC_PATH = DEF(GCC5_IA32_PREFIX)objcopy
+
+*_CLANG38_IA32_ASLCC_FLAGS = -x c -Os -m32 DEF(CLANG38_IA32_TARGET) -flto

Does LTO make any sense for ACPI tables?

+*_CLANG38_IA32_ASLDLINK_FLAGS = DEF(GCC5_IA32_X64_DLINK_FLAGS) -Wl,-Oz -Wl,-melf_i386 -Wl,--entry,ReferenceAcpiTable -Wl,-u,ReferenceAcpiTable
+*_CLANG38_IA32_ASM_FLAGS = DEF(GCC5_ASM_FLAGS) -m32 -march=i386 DEF(CLANG38_IA32_TARGET)
+DEBUG_CLANG38_IA32_CC_FLAGS = DEF(CLANG38_ALL_CC_FLAGS) -m32 -Oz -flto -march=i586 DEF(CLANG38_IA32_TARGET) -g
+RELEASE_CLANG38_IA32_CC_FLAGS = DEF(CLANG38_ALL_CC_FLAGS) -m32 -Oz -flto -march=i586 DEF(CLANG38_IA32_TARGET)
+*_CLANG38_IA32_DLINK_FLAGS = DEF(GCC5_IA32_X64_DLINK_FLAGS) -Wl,-Oz -Wl,-melf_i386 -Wl,--oformat=elf32-i386
+*_CLANG38_IA32_DLINK2_FLAGS = DEF(GCC5_IA32_DLINK2_FLAGS)
+*_CLANG38_IA32_RC_FLAGS = DEF(GCC_IA32_RC_FLAGS)
+*_CLANG38_IA32_OBJCOPY_FLAGS =
+*_CLANG38_IA32_NASM_FLAGS = -f elf32
+*_CLANG38_IA32_PP_FLAGS = DEF(GCC_PP_FLAGS) DEF(CLANG38_IA32_TARGET)
+*_CLANG38_IA32_ASLPP_FLAGS = DEF(GCC_ASLPP_FLAGS) DEF(CLANG38_IA32_TARGET)
+*_CLANG38_IA32_VFRPP_FLAGS = DEF(GCC_VFRPP_FLAGS) DEF(CLANG38_IA32_TARGET)
+
+##########################
+# CLANG38 X64 definitions
+##########################
+*_CLANG38_X64_OBJCOPY_PATH = DEF(GCC5_X64_PREFIX)objcopy
+*_CLANG38_X64_CC_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_SLINK_PATH = DEF(CLANG38_X64_PREFIX)llvm-ar
+*_CLANG38_X64_DLINK_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_ASLDLINK_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_ASM_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_PP_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_VFRPP_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_ASLCC_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_ASLPP_PATH = DEF(CLANG38_X64_PREFIX)clang
+*_CLANG38_X64_RC_PATH = DEF(GCC5_X64_PREFIX)objcopy
+
+*_CLANG38_X64_ASLCC_FLAGS = -x c -Os -m64 -flto DEF(CLANG38_X64_TARGET)
+*_CLANG38_X64_ASLDLINK_FLAGS = DEF(GCC5_IA32_X64_DLINK_FLAGS) -Wl,-Oz -Wl,-melf_x86_64 -Wl,--entry,ReferenceAcpiTable -Wl,-u,ReferenceAcpiTable -Wl,-pie -mcmodel=small
+*_CLANG38_X64_ASM_FLAGS = DEF(GCC5_ASM_FLAGS) -m64 DEF(CLANG38_X64_TARGET)
+DEBUG_CLANG38_X64_CC_FLAGS = DEF(CLANG38_ALL_CC_FLAGS) -m64 "-DEFIAPI=__attribute__((ms_abi))" -mno-red-zone -mcmodel=small -fpie -Oz -flto DEF(CLANG38_X64_TARGET) -g
+RELEASE_CLANG38_X64_CC_FLAGS = DEF(CLANG38_ALL_CC_FLAGS) -m64 "-DEFIAPI=__attribute__((ms_abi))" -mno-red-zone -mcmodel=small -fpie -Oz -flto DEF(CLANG38_X64_TARGET)
+*_CLANG38_X64_DLINK_FLAGS = DEF(GCC5_IA32_X64_DLINK_FLAGS) -Wl,-Oz -Wl,-melf_x86_64 -Wl,--oformat=elf64-x86-64 -Wl,-pie -mcmodel=small
+*_CLANG38_X64_DLINK2_FLAGS = DEF(GCC5_X64_DLINK2_FLAGS)
+*_CLANG38_X64_RC_FLAGS = DEF(GCC_X64_RC_FLAGS)
+*_CLANG38_X64_OBJCOPY_FLAGS =
+*_CLANG38_X64_NASM_FLAGS = -f elf64
+*_CLANG38_X64_PP_FLAGS = DEF(GCC_PP_FLAGS) DEF(CLANG38_X64_TARGET)
+*_CLANG38_X64_ASLPP_FLAGS = DEF(GCC_ASLPP_FLAGS) DEF(CLANG38_X64_TARGET)
+*_CLANG38_X64_VFRPP_FLAGS = DEF(GCC_VFRPP_FLAGS) DEF(CLANG38_X64_TARGET)
+
+####################################################################################
+#
# Cygwin GCC And Intel ACPI Compiler
#
####################################################################################
--
2.7.4

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