Live ranges with a constrained register class may benefit from splitting
around individual uses. It allows the remaining live range to use a
larger register class where it may allocate. This is like spilling to a
different register class.

This is only attempted on constrained register classes.

<rdar://problem/11438902>

llvm-svn: 157354

The dead code elimination with callbacks is still useful.

llvm-svn: 157100

llvm-svn: 153906

This is just the fallback tie-breaker ordering, the main allocation
order is still descending size.

Patch by Shamil Kurmangaleev!

llvm-svn: 153904

Refactored the LiveRangeEdit interface so that MachineFunction, TargetInstrInfo, MachineRegisterInfo, LiveIntervals, and VirtRegMap are all passed into the constructor and stored as members instead of passed in to each method.

llvm-svn: 153903

llvm-svn: 152001

Passes after RegAlloc should be able to rely on MRI->getNumVirtRegs() == 0.
This makes sharing code for pre/postRA passes more robust.
Now, to check if a pass is running before the RA pipeline begins, use MRI->isSSA().
To check if a pass is running after the RA pipeline ends, use !MRI->getNumVirtRegs().

PEI resets virtual regs when it's done scavenging.

PTX will either have to provide its own PEI pass or assign physregs.

llvm-svn: 151032

Perform all comparisons at instruction granularity, and make sure
register masks on uses count in both gaps.

llvm-svn: 150530

Again the goal is to produce identical assembly with register mask
operands enabled.

llvm-svn: 150287

This makes global live range splitting behave identically with and
without register mask operands.

This is not necessarily the best way of using register masks for live
range splitting.  It would be more efficient to first split global live
ranges around calls (i.e., register masks), and reserve the fine grained
per-physreg interference guidance for global live ranges that do not
cross calls.

For now the goal is to produce identical assembly when enabling register
masks.

llvm-svn: 150259

Creates a configurable regalloc pipeline.

Ensure specific llc options do what they say and nothing more: -reglloc=... has no effect other than selecting the allocator pass itself. This patch introduces a new umbrella flag, "-optimize-regalloc", to enable/disable the optimizing regalloc "superpass". This allows for example testing coalscing and scheduling under -O0 or vice-versa.

When a CodeGen pass requires the MachineFunction to have a particular property, we need to explicitly define that property so it can be directly queried rather than naming a specific Pass. For example, to check for SSA, use MRI->isSSA, not addRequired<PHIElimination>.

CodeGen transformation passes are never "required" as an analysis

ProcessImplicitDefs does not require LiveVariables.

We have a plan to massively simplify some of the early passes within the regalloc superpass.

llvm-svn: 150226

This only adds the interference checks required for correctness.
We still need to take advantage of register masks for the
interference driven live range splitting.

llvm-svn: 150191

Responding to code review.

llvm-svn: 148290

More short term hackery until we have a way to configure passes that work on LiveIntervals.

llvm-svn: 148289

llvm-svn: 148105

llvm-svn: 148031

llvm-svn: 147979

Nobody cared, StackSlotColoring scans the instructions to find used stack
slots.

llvm-svn: 144485

No test case, spotted by inspection.

llvm-svn: 143407

THe LRE_DidCloneVirtReg callback may be called with vitual registers
that RAGreedy doesn't even know about yet.  In that case, there are no
data structures to update.

llvm-svn: 139702

It has been enabled by default for a while, it was only there to allow
performance comparisons.

llvm-svn: 139501

SplitKit always computes a complement live range to cover the places
where the original live range was live, but no explicit region has been
allocated.

Currently, the complement live range is created to be as small as
possible - it never overlaps any of the regions.  This minimizes
register pressure, but if the complement is going to be spilled anyway,
that is not very important.  The spiller will eliminate redundant
spills, and hoist others by making the spill slot live range overlap
some of the regions created by splitting.  Stack slots are cheap.

This patch adds the interface to enable spill modes in SplitKit.  In
spill mode, SplitKit will assume that the complement is going to spill,
so it will allow it to overlap regions in order to avoid back-copies.
By doing some of the spiller's work early, the complement live range
becomes simpler.  In some cases, it can become much simpler because no
extra PHI-defs are required.  This will speed up both splitting and
spilling.

This is only the interface to enable spill modes, no implementation yet.

llvm-svn: 139500

llvm-svn: 138025

A public interface is no longer needed since RegisterCoalescer is not an
analysis any more.

llvm-svn: 137082

llvm-svn: 137023

All new local ranges are marked as RS_New now, so there is no need to
attempt splitting of RS_Spill ranges any more.

llvm-svn: 137002

The local ranges created get to stay in the RS_New stage, just like for
local and region splitting.

This gives tryLocalSplit a bit more freedom the first time it sees one
of these new local ranges.

llvm-svn: 137001

llvm-svn: 136996

No functional change.

llvm-svn: 136994

Drop the use of SplitAnalysis::getMultiUseBlocks, there is no need to go
through a SmallPtrSet any more.

llvm-svn: 136992

Normally, we don't create a live range for a single instruction in a
basic block, the spiller does that anyway. However, when splitting a
live range that belongs to a proper register sub-class, inserting these
extra COPY instructions completely remove the constraints from the
remainder interval, and it may be allocated from the larger super-class.

The spiller will mop up these small live ranges if we end up spilling
anyway. It calls them snippets.

llvm-svn: 136989

This helps generate better code in functions with high register
pressure.

The previous version of compact region splitting caused regressions
because the regions were a bit too large. A stronger negative bias
applied in r136832 fixed this problem.

llvm-svn: 136836

Apply twice the negative bias on transparent blocks when computing the
compact regions. This excludes loop backedges from the region when only
one of the loop blocks uses the register.

Previously, we would include the backedge in the region if the loop
preheader and the loop latch both used the register, but the loop header
didn't.

When both the header and latch blocks use the register, we still keep it
live on the backedge.

llvm-svn: 136832

lib/CodeGen/RegAllocGreedy.cpp:1176:18: warning: unused variable 'B' [-Wunused-variable]
    if (unsigned B = Cand.getBundles(BundleCand, BestCand)) {
                 ^
lib/CodeGen/RegAllocGreedy.cpp:1188:18: warning: unused variable 'B' [-Wunused-variable]
    if (unsigned B = Cand.getBundles(BundleCand, 0)) {
                 ^

llvm-svn: 136831

llvm-svn: 136742

This information is not used for anything yet.

llvm-svn: 136741

With a 'FirstDef' field right there, it is very confusing that FirstUse
refers to an instruction that may be a def.

llvm-svn: 136739

llvm-svn: 136584

While this generally helped x86-64, there was some large regressions
for i386.

llvm-svn: 136571

This helps generate better code in functions with high register
pressure.

llvm-svn: 136528