Quentin Colombet fb57392a8d [RegAlloc] Make tryInstructionSplit less aggressive. ... The greedy register allocator tries to split a live-range around each instruction where it is used or defined to relax the constraints on the entire live-range (this is a last chance split before falling back to spill). The goal is to have a big live-range that is unconstrained (i.e., that can use the largest legal register class) and several small local live-range that carry the constraints implied by each instruction. E.g., Let csti be the constraints on operation i. V1= op1 V1(cst1) op2 V1(cst2) V1 live-range is constrained on the intersection of cst1 and cst2. tryInstructionSplit relaxes those constraints by aggressively splitting each def/use point: V1= V2 = V1 V3 = V2 op1 V3(cst1) V4 = V2 op2 V4(cst2) Because of how the coalescer infrastructure works, each new variable (V3, V4) that is alive at the same time as V1 (or its copy, here V2) interfere with V1. Thus, we end up with an uncoalescable copy for each split point. To make tryInstructionSplit less aggressive, we check if the split point actually relaxes the constraints on the whole live-range. If it does not, we do not insert it. Indeed, it will not help the global allocation problem: - V1 will have the same constraints. - V1 will have the same interference + possibly the newly added split variable VS. - VS will produce an uncoalesceable copy if alive at the same time as V1. <rdar://problem/15570057> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198369 91177308-0d34-0410-b5e6-96231b3b80d8		2014-01-02 22:47:22 +00:00
..
Analysis	BasicAA: Fix value equality and phi cycles	2014-01-02 03:31:36 +00:00
AsmParser	Begin adding docs and IR-level support for the inalloca attribute	2013-12-19 02:14:12 +00:00
Bitcode	Begin adding docs and IR-level support for the inalloca attribute	2013-12-19 02:14:12 +00:00
CodeGen	[RegAlloc] Make tryInstructionSplit less aggressive.	2014-01-02 22:47:22 +00:00
DebugInfo	DebugInfo: Move type units into the debug_types section with appropriate comdat grouping and type unit headers	2013-12-13 21:33:40 +00:00
ExecutionEngine	There are no __register_frame and __deregister_frame functions	2013-12-17 08:40:11 +00:00
IR	Allow addrspacecast in global aliases	2014-01-02 20:55:01 +00:00
IRReader	[llvm-c] Expose IRReader interface	2013-11-06 09:21:15 +00:00
Linker	Revert "Move copying of global initializers below the cloning of functions."	2013-11-09 00:43:18 +00:00
LTO	Add TargetLibraryInfo in LTO passes builder	2013-12-12 01:37:39 +00:00
MC	AsmParser: cleanup diagnostics for .rep/.rept	2013-12-28 06:39:29 +00:00
Object	Support for microMIPS TLS relocations.	2013-12-19 16:02:32 +00:00
Option	Avoid buffer copies when a Twine already is a StringRef.	2013-12-03 18:18:28 +00:00
Support	Make llvm::Regex non-copyable but movable.	2014-01-02 19:04:59 +00:00
TableGen	[TableGen] Correctly generate implicit anonymous prototype defs in multiclasses	2014-01-02 20:47:09 +00:00
Target	[PPC] Fix comment to match function name	2014-01-02 22:09:39 +00:00
Transforms	Disable compare sinking in CodeGenPrepare when multiple condition registers are available	2014-01-02 21:13:43 +00:00
CMakeLists.txt	Move LTO support library to a component, allowing it to be tested	2013-09-24 23:52:22 +00:00
LLVMBuild.txt	Move LTO support library to a component, allowing it to be tested	2013-09-24 23:52:22 +00:00
Makefile	Reformat Makefile. No other changes.	2013-10-30 04:03:03 +00:00