Commit Graph

115 Commits

Author SHA1 Message Date
Jakob Stoklund Olesen
4314268128 Replace TargetRegisterInfo::printReg with a PrintReg class that also works without a TRI instance.
Print virtual registers numbered from 0 instead of the arbitrary
FirstVirtualRegister. The first virtual register is printed as %vreg0.
TRI::NoRegister is printed as %noreg.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123107 91177308-0d34-0410-b5e6-96231b3b80d8
2011-01-09 03:05:53 +00:00
Eric Christopher
f299da8ec3 Fix comment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121285 91177308-0d34-0410-b5e6-96231b3b80d8
2010-12-08 21:35:09 +00:00
Owen Anderson
081c34b725 Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which
must be called in the pass's constructor.  This function uses static dependency declarations to recursively initialize
the pass's dependencies.

Clients that only create passes through the createFooPass() APIs will require no changes.  Clients that want to use the
CommandLine options for passes will need to manually call the appropriate initialization functions in PassInitialization.h
before parsing commandline arguments.

I have tested this with all standard configurations of clang and llvm-gcc on Darwin.  It is possible that there are problems
with the static dependencies that will only be visible with non-standard options.  If you encounter any crash in pass
registration/creation, please send the testcase to me directly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116820 91177308-0d34-0410-b5e6-96231b3b80d8
2010-10-19 17:21:58 +00:00
Devang Patel
4bafda9618 Add DEBUG message.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113614 91177308-0d34-0410-b5e6-96231b3b80d8
2010-09-10 20:32:09 +00:00
Jim Grosbach
ee72651df4 previous patch was a little too tricky for its own good. Don't try to
overload UserInInstr. Explicitly check Allocatable. The early exit in the
condition will mean the performance impact of the extra test should be
minimal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113016 91177308-0d34-0410-b5e6-96231b3b80d8
2010-09-03 21:45:15 +00:00
Jim Grosbach
1f758831cb The register allocator shouldn't consider allocating reserved registers.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112728 91177308-0d34-0410-b5e6-96231b3b80d8
2010-09-01 19:28:41 +00:00
Jim Grosbach
07cb689d62 tidy up a few 80-column and trailing whitespace bits.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112726 91177308-0d34-0410-b5e6-96231b3b80d8
2010-09-01 19:16:29 +00:00
Jakob Stoklund Olesen
9d4b51b696 Ignore unallocatable registers in RegAllocFast.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112632 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-31 19:54:25 +00:00
Eli Friedman
24a1182184 Delete dead comment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111744 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-21 20:19:51 +00:00
Owen Anderson
90c579de5a Reapply r110396, with fixes to appease the Linux buildbot gods.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110460 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-06 18:33:48 +00:00
Devang Patel
31defcf234 While emitting DBG_VALUE for registers spilled at the end of a block do not use location of MBB->end(). If a block does not have terminator then incoming iterator points to end().
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110411 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-06 00:26:18 +00:00
Owen Anderson
1f74590e9d Revert r110396 to fix buildbots.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110410 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-06 00:23:35 +00:00
Owen Anderson
9ccaf53ada Don't use PassInfo* as a type identifier for passes. Instead, use the address of the static
ID member as the sole unique type identifier.  Clean up APIs related to this change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110396 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-05 23:42:04 +00:00
Devang Patel
459a36bd34 While spilling live registers at the end of block check whether they are used by DBG_VALUE machine instructions or not. If a spilled register is used by DBG_VALUE machine instruction then insert a new DBG_VALUE machine instruction to encode variable's new location on stack.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110235 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-04 18:42:02 +00:00
Jakob Stoklund Olesen
4bd94f7bbe Fix a bug in the -regalloc=fast handling of exotic two-address instruction with
multiple defs, like t2LDRSB_POST.

The first def could accidentally steal the physreg that the second, tied def was
required to be allocated to.

Now, the tied use-def is treated more like an early clobber, and the physreg is
reserved before allocating the other defs.

This would never be a problem when the tied def was the only def which is the
usual case.

This fixes MallocBench/gs for thumb2 -O0.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109715 91177308-0d34-0410-b5e6-96231b3b80d8
2010-07-29 00:52:19 +00:00
Devang Patel
58b8176ed3 Fix memory leak reported by valgrind.
Do not visit operands of old instruction. Visit all operands of new instruction.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108767 91177308-0d34-0410-b5e6-96231b3b80d8
2010-07-19 23:25:39 +00:00
Jakob Stoklund Olesen
04c528a0c8 Remove many calls to TII::isMoveInstr. Targets should be producing COPY anyway.
TII::isMoveInstr is going tobe completely removed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108507 91177308-0d34-0410-b5e6-96231b3b80d8
2010-07-16 04:45:42 +00:00
Devang Patel
7a029b6d7e Update DBG_VALUE to refer appropriate stack slot in case of a spill.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108023 91177308-0d34-0410-b5e6-96231b3b80d8
2010-07-09 21:48:31 +00:00
Jakob Stoklund Olesen
273f7e4299 Detect and handle COPY in many places.
This code is transitional, it will soon be possible to eliminate
isExtractSubreg, isInsertSubreg, and isMoveInstr in most places.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107547 91177308-0d34-0410-b5e6-96231b3b80d8
2010-07-03 00:04:37 +00:00
Jakob Stoklund Olesen
d1303d2a66 Fix the handling of partial redefines in the fast register allocator.
A partial redefine needs to be treated like a tied operand, and the register
must be reloaded while processing use operands.

This fixes a bug where partially redefined registers were processed as normal
defs with a reload added. The reload could clobber another use operand if it was
a kill that allowed register reuse.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107193 91177308-0d34-0410-b5e6-96231b3b80d8
2010-06-29 19:15:30 +00:00
Jakob Stoklund Olesen
d843b3925f Add more special treatment for inline asm in RegAllocFast.
When an instruction has tied operands and physreg defines, we must take extra
care that the tied operands conflict with neither physreg defs nor uses.

The special treatment is given to inline asm and instructions with tied operands
/ early clobbers and physreg defines.

This fixes PR7509.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107043 91177308-0d34-0410-b5e6-96231b3b80d8
2010-06-28 18:34:34 +00:00
Jakob Stoklund Olesen
75ac4d9c2d Avoid processing early clobbers twice in RegAllocFast.
Early clobbers defining a virtual register were first alocated to a physreg and
then processed as a physreg EC, spilling the virtreg.

This fixes PR7382.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105998 91177308-0d34-0410-b5e6-96231b3b80d8
2010-06-15 16:20:57 +00:00
Jakob Stoklund Olesen
6de07178e1 Keep track of the call instructions whose clobber lists were skipped during fast
register allocation.

Process all of the clobber lists at the end of the function, marking the
registers as used in MachineRegisterInfo.

This is necessary in case the calls clobber callee-saved registers (sic).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105473 91177308-0d34-0410-b5e6-96231b3b80d8
2010-06-04 18:08:29 +00:00
Jakob Stoklund Olesen
d32e735ae6 Add support for partial redefs to the fast register allocator.
A partial redef now triggers a reload if required. Also don't add
<imp-def,dead> operands for physical superregisters.

Kill flags are still treated as full register kills, and <imp-use,kill> operands
are added for physical superregisters as before.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104167 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-19 21:36:05 +00:00
Jakob Stoklund Olesen
0eeb05c969 Properly handle multiple definitions of a virtual register in the same
instruction.

This can happen on ARM:

>> %reg1035:5<def>, %reg1035:6<def> = VLD1q16 %reg1028, 0, pred:14, pred:%reg0
Regs: Q0=%reg1032* R0=%reg1028* R1=%reg1029* R2 R3=%reg1031*
Killing last use: %reg1028
Allocating %reg1035 from QPR
Assigning %reg1035 to Q1
<< %D2<def>, %D3<def> = VLD1q16 %R0<kill>, 0, pred:14, pred:%reg0, %Q1<imp-def>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104056 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-18 21:10:50 +00:00
Jakob Stoklund Olesen
b8acb7be80 Pull the UsedInInstr.test() calls into calcSpillCost() and remember aliases.
This fixes the miscompilations of MultiSource/Applications/JM/l{en,de}cod.
Clang now successfully self hosts in a debug build with the fast register allocator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103975 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 21:02:08 +00:00
Jakob Stoklund Olesen
2997985b4c Remove debug option. Add comment on spill order determinism.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103961 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 20:01:22 +00:00
Jakob Stoklund Olesen
aa4b0159da Avoid allocating the same physreg to multiple virtregs in one instruction.
While that approach works wonders for register pressure, it tends to break
everything.

This should unbreak the arm-linux builder and fix a number of miscompilations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103946 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 17:18:59 +00:00
Jakob Stoklund Olesen
f3ea06b108 Minor optimizations. DenseMap::begin() is surprisingly slow on an empty map.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103940 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 15:30:37 +00:00
Jakob Stoklund Olesen
548643c573 Extract spill cost calculation to a new method, and use definePhysReg() to clear
out aliases when allocating. Clean up allocVirtReg().

Use calcSpillCost() to allow more aggressive hinting. Now the hint is always
taken unless blocked by a reserved register. This leads to more coalescing,
lower register pressure, and less spilling.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103939 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 15:30:32 +00:00
Jakob Stoklund Olesen
0c9e4f5f3f Only use clairvoyance when defining a register, and then only if it has one use.
This makes allocation independent on the ordering of use-def chains.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103935 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 04:50:57 +00:00
Jakob Stoklund Olesen
646dd7c899 Eliminate a hash table probe when killing virtual registers.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103934 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 03:26:09 +00:00
Jakob Stoklund Olesen
ac3e529831 Execute virtreg kills immediately instead of after processing all uses.
This is safe to do because the physreg has been marked UsedInInstr and the kill flag will be set on the last operand using the virtreg if there are more then one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103933 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 03:26:06 +00:00
Jakob Stoklund Olesen
41e1401de5 Sprinkle superregister <imp-def> and <imp-kill> operands when dealing with subregister indices.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103931 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 02:49:21 +00:00
Jakob Stoklund Olesen
4b6bbe885d Now that we don't keep live registers across calls, there is not reason to go
through the very long list of call-clobbered registers. We just assume all
registers are clobbered.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103930 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 02:49:18 +00:00
Jakob Stoklund Olesen
844db9cc6f Boldly attempt consistent capitalization. Functional changes unintended.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103929 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 02:49:15 +00:00
Jakob Stoklund Olesen
e6aba83797 Spill and kill all virtual registers across a call.
Debug code doesn't use callee saved registers anyway, and the code is simpler this way. Now spillVirtReg always kills, and the isKill parameter is not needed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103927 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 02:07:32 +00:00
Jakob Stoklund Olesen
01dcbf8507 Reduce hashtable probes by using DenseMap::insert() for lookup.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103926 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 02:07:29 +00:00
Jakob Stoklund Olesen
6fb69d85e9 Make MBB a class member instead of passing it around everywhere.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103925 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 02:07:22 +00:00
Chandler Carruth
2c13ab2bb8 Fix an GCC warning that seems to have actually caught a bug (!!!) in
a condition's grouping. Every other use of Allocatable.test(Hint) groups it the
same way as it is indented, so move the parentheses to agree with that
grouping.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103869 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-15 10:23:23 +00:00
Jakob Stoklund Olesen
1e03ff4243 Calculate liveness on the fly for local registers.
When working top-down in a basic block, substituting physregs for virtregs, the use-def chains are kept up to date. That means we can recognize a virtreg kill by the use-def chain becoming empty.

This makes the fast allocator independent of incoming kill flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103866 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-15 06:09:08 +00:00
Jakob Stoklund Olesen
6a6328ba3d Don't bother spilling before a return
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103831 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 22:40:43 +00:00
Jakob Stoklund Olesen
efa155fd6e Track allocatable instead of reserved regs, and never take an unallocatable hint.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103828 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 22:02:56 +00:00
Jakob Stoklund Olesen
e97dda4fc5 Avoid scanning the long tail of physreg operands on calls
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103823 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 21:55:52 +00:00
Jakob Stoklund Olesen
8a65c510a4 Count coalesced copies
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103821 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 21:55:50 +00:00
Jakob Stoklund Olesen
a0e618de5d Allow virtreg redefines when verifying for RegAllocFast
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103820 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 21:55:44 +00:00
Jakob Stoklund Olesen
1b2c761a9c When verifying two-address instructions, check the following:
- Kill is implicit when use and def registers are identical.
- Only virtual registers can differ.

Add a -verify-fast-regalloc to run the verifier before the fast allocator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103797 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 20:28:32 +00:00
Jakob Stoklund Olesen
4ed1082683 Simplify the handling of physreg defs and uses in RegAllocFast.
This adds extra security against using clobbered physregs, and it adds kill
markers to physreg uses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103784 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 18:03:25 +00:00
Jakob Stoklund Olesen
7ff82e1501 Enable opportunistic coalescing
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103764 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 04:30:51 +00:00
Jakob Stoklund Olesen
57b6076d34 Trust kill flags from isel and later passes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103748 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 00:02:23 +00:00
Jakob Stoklund Olesen
7d4f25904d Fix an embarrassing runtime regression for RegAllocFast.
This loop is quadratic in the capacity for a DenseMap:

  while(!map.empty())
    map.erase(map.begin());

Instead we now do a normal begin() - end() iteration followed by map.clear().
That also has the nice sideeffect of shrinking the map capacity on demand.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103747 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 00:02:20 +00:00
Jakob Stoklund Olesen
c9c4dacd03 Clean up RegAllocFast debug output
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103739 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-13 20:43:17 +00:00
Jakob Stoklund Olesen
4bf4bafcce Take allocation hints from copy instructions to/from physregs.
This causes way more identity copies to be generated, ripe for coalescing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103686 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-13 00:19:43 +00:00
Jakob Stoklund Olesen
63e34f690c More asserts around physreg uses
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103685 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-13 00:19:39 +00:00
Jakob Stoklund Olesen
804291e316 Make sure to add kill flags to the last use of a virtreg when it is redefined.
The X86 floating point stack pass and others depend on good kill flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103635 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-12 18:46:03 +00:00
Jakob Stoklund Olesen
1a1ad578a3 Avoid scoping issues, fix buildbots
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103530 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-12 00:11:19 +00:00
Daniel Dunbar
0efd768aea Make Clang happy.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103528 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-11 23:53:13 +00:00
Jakob Stoklund Olesen
210e2afcc7 Store the Dirty bit in the LiveReg structure instead of a bit vector.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103522 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-11 23:24:47 +00:00
Jakob Stoklund Olesen
76b4d5a021 Keep track of the last place a live virtreg was used.
This allows us to add accurate kill markers, something the scavenger likes.
Add some more tests from ARM that needed this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103521 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-11 23:24:45 +00:00
Jakob Stoklund Olesen
82b07dc499 Simplify the tracking of used physregs to a bulk bitor followed by a transitive
closure after allocating all blocks.

Add a few more test cases for -regalloc=fast.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103500 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-11 20:30:28 +00:00
Jakob Stoklund Olesen
bbf33b38aa Mostly rewrite RegAllocFast.
Sorry for the big change. The path leading up to this patch had some TableGen
changes that I didn't want to commit before I knew they were useful. They
weren't, and this version does not need them.

The fast register allocator now does no liveness calculations. Instead it relies
on kill flags provided by isel. (Currently those kill flags are also ignored due
to isel bugs). The allocation algorithm is supposed to work with any subset of
valid kill flags. More kill flags simply means fewer spills inserted.

Registers are allocated from a working set that contains no aliases. That means
most allocations can be done directly without expensive alias checks. When the
working set runs out of registers we do the full alias check to find new free
registers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103488 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-11 18:54:45 +00:00
Evan Cheng
31b9c44cc1 It's not safe eliminate copies where src and dst have different sub-register indices.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103450 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-11 00:20:03 +00:00
Evan Cheng
746ad69e08 Add argument TargetRegisterInfo to loadRegFromStackSlot and storeRegToStackSlot.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103193 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-06 19:06:44 +00:00
Jakob Stoklund Olesen
a063e19593 Run LiveVariables instead of computing liveness locally in -regalloc=fast.
This actually makes everything slower, but the plan is to have isel add <kill>
flags the way it is already adding <dead> flags. Then LiveVariables can be
removed again.

When ignoring the time spent in LiveVariables, -regalloc=fast is now twice as
fast as -regalloc=local.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102034 91177308-0d34-0410-b5e6-96231b3b80d8
2010-04-21 23:18:07 +00:00
Jakob Stoklund Olesen
00207237dd Add fast register allocator, enabled with -regalloc=fast.
So far this is just a clone of -regalloc=local that has been lobotomized to run
25% faster. It drops the least-recently-used calculations, and is just plain
stupid when it runs out of registers.

The plan is to make this go even faster for -O0 by taking advantage of the short
live intervals in unoptimized code. It should not be necessary to calculate
liveness when most virtual registers are killed 2-3 instructions after they are
born.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102006 91177308-0d34-0410-b5e6-96231b3b80d8
2010-04-21 18:02:42 +00:00