Bruno Cardoso Lopes 6bf5b2b094 [AsmPrinter] Access pointers to globals via pcrel GOT entries ... Front-ends could use global unnamed_addr to hold pointers to other symbols, like @gotequivalent below: @foo = global i32 42 @gotequivalent = private unnamed_addr constant i32* @foo @delta = global i32 trunc (i64 sub (i64 ptrtoint (i32** @gotequivalent to i64), i64 ptrtoint (i32* @delta to i64)) to i32) The global @delta holds a data "PC"-relative offset to @gotequivalent, an unnamed pointer to @foo. The darwin/x86-64 assembly output for this follows: .globl _foo _foo: .long 42 .globl _gotequivalent _gotequivalent: .quad _foo .globl _delta _delta: .long _gotequivalent-_delta Since unnamed_addr indicates that the address is not significant, only the content, we can optimize the case above by replacing pc-relative accesses to "GOT equivalent" globals, by a PC relative access to the GOT entry of the final symbol instead. Therefore, "delta" can contain a pc relative relocation to foo's GOT entry and we avoid the emission of "gotequivalent", yielding the assembly code below: .globl _foo _foo: .long 42 .globl _delta _delta: .long _foo@GOTPCREL+4 There are a couple of advantages of doing this: (1) Front-ends that need to emit a great deal of data to store pointers to external symbols could save space by not emitting such "got equivalent" globals and (2) IR constructs combined with this opt opens a way to represent GOT pcrel relocations by using the LLVM IR, which is something we previously had no way to express. Differential Revision: http://reviews.llvm.org/D6922 rdar://problem/18534217 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230264 91177308-0d34-0410-b5e6-96231b3b80d8		2015-02-23 21:26:18 +00:00
..
AddressPool.cpp
AddressPool.h
ARMException.cpp
AsmPrinter.cpp	[AsmPrinter] Access pointers to globals via pcrel GOT entries	2015-02-23 21:26:18 +00:00
AsmPrinterDwarf.cpp	Migrate away a use of the subtarget (and TargetMachine) from	2015-02-19 23:29:42 +00:00
AsmPrinterHandler.h
AsmPrinterInlineAsm.cpp	Unconditionally create a new MCInstrInfo in the asm printer for	2015-02-21 09:09:15 +00:00
ByteStreamer.h
CMakeLists.txt
DbgValueHistoryCalculator.cpp
DbgValueHistoryCalculator.h
DebugLocEntry.h
DebugLocList.h
DIE.cpp
DIEHash.cpp
DIEHash.h
DwarfAccelTable.cpp
DwarfAccelTable.h	Removing LLVM_DELETED_FUNCTION, as MSVC 2012 was the last reason for requiring the macro. NFC; LLVM edition.	2015-02-15 22:54:22 +00:00
DwarfCFIException.cpp
DwarfCompileUnit.cpp	Used the cached subtarget off of the MachineFunction.	2015-02-20 22:36:11 +00:00
DwarfCompileUnit.h
DwarfDebug.cpp	Used the cached subtarget off of the MachineFunction.	2015-02-20 22:36:11 +00:00
DwarfDebug.h	80-column fixups.	2015-02-17 20:02:28 +00:00
DwarfException.h
DwarfExpression.cpp	AsmPrinter: Take range in DwarfExpression::AddExpression(), NFC	2015-02-17 22:30:56 +00:00
DwarfExpression.h	AsmPrinter: Take range in DwarfExpression::AddExpression(), NFC	2015-02-17 22:30:56 +00:00
DwarfFile.cpp
DwarfFile.h
DwarfStringPool.cpp
DwarfStringPool.h
DwarfUnit.cpp	Make the ARM AsmPrinter independent of global subtarget	2015-02-17 20:02:32 +00:00
DwarfUnit.h
EHStreamer.cpp
EHStreamer.h
ErlangGCPrinter.cpp
LLVMBuild.txt
Makefile
OcamlGCPrinter.cpp
Win64Exception.cpp
Win64Exception.h
WinCodeViewLineTables.cpp
WinCodeViewLineTables.h