Commit Graph

12986 Commits

Author SHA1 Message Date
Colin LeMahieu
c2d30aebf3 [Hexagon] Reverting r231699
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231703 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-09 21:19:02 +00:00
Colin LeMahieu
8c2919a34e [Hexagon] Updating constant set to simpler versions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231699 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-09 20:33:12 +00:00
Colin LeMahieu
a0ce232a65 [Hexagon] Eliminating immediate condition set.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231693 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-09 19:57:18 +00:00
Rafael Espindola
be886690bd Print jump tables before exception tables.
In the case where just tables are part of the function section, this produces
more readable assembly by avoiding switching to the eh section and back
to .text.

This would also break with non unique section names, as trying to switch to
a unique section actually creates a new one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231677 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-09 18:29:12 +00:00
Reed Kotler
18afdb3210 Add logical ops to Mips fast-isel
Summary:
Code is mostly copied from AArch64 port and modified where needed for Mips.

This handles the "non" legal cases of logical ops. Legal cases are handled by tablegen patterns.

Test Plan:
Make check test logopm.ll

All of test-suite passes at O0/O2 and mips32 r1/r2 with this new change.

Reviewers: dsanders

Reviewed By: dsanders

Subscribers: echristo, llvm-commits, aemerson, rfuhler

Differential Revision: http://reviews.llvm.org/D6599

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231665 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-09 16:28:10 +00:00
Marek Olsak
c4ca7b59db R600/SI: Limit SGPRs to 80 on Tonga and Iceland
This is a candidate for stable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231659 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-09 15:48:09 +00:00
Andrea Di Biagio
d1232fa1c0 Fix line ending in test CodeGen/X86/pr22774.ll. NFC.
Also, replaced line with 'target triple' with flag -mtriple on the RUN line.
Removed the data layout string as it is not needed.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231654 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-09 15:02:01 +00:00
Andrea Di Biagio
692f7382b5 [X86][AVX] Fix wrong lowering of VPERM2X128 nodes
There were cases where the backend computed a wrong permute mask for a VPERM2X128 node.

Example:
\code
define <8 x float> @foo(<8 x float> %a, <8 x float> %b) {
  %shuffle = shufflevector <8 x float> %a, <8 x float> %b, <8 x i32> <i32 undef, i32 undef, i32 6, i32 7, i32 undef, i32 undef, i32 6, i32 7>
  ret <8 x float> %shuffle
}
\code end

Before this patch, llc (with -mattr=+avx) emitted the following vperm2f128:
  vperm2f128 $0, %ymm0, %ymm0, %ymm0  # ymm0 = ymm0[0,1,0,1]

With this patch, llc emits a vperm2f128 with a correct permute mask:
  vperm2f128 $17, %ymm0, %ymm0, %ymm0  # ymm0 = ymm0[2,3,2,3]

Differential Revision: http://reviews.llvm.org/D8119


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231601 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-08 16:28:47 +00:00
Andrea Di Biagio
15d2c3fb00 [DAGCombiner] Fix wrong folding of AND dag nodes.
This patch fixes the logic in the DAGCombiner that folds an AND node according
to rule: (and (X (load V)), C) -> (X (load V))

An AND between a vector load 'X' and a constant build_vector 'C' can be folded
into the load itself only if we can prove that the AND operation is redundant.
The algorithm implemented by 'visitAND' firstly computes the splat value 'S'
from C, and then checks if S has the lower 'B' bits set (where B is the size in
bits of the vector element type). The algorithm takes into account also the
'undef' bits in the splat mask.

Unfortunately, the algorithm only worked under the assumption that the size of S
is a multiple of the vector element type. With this patch, we conservatively
avoid folding the AND if the splat bits are not compatible with the vector
element type.

Added X86 test and-load-fold.ll

Differential Revision: http://reviews.llvm.org/D8085


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231563 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-07 12:24:55 +00:00
Simon Pilgrim
62ba058dea [DAGCombiner] SCALAR_TO_VECTOR(EXTRACT_VECTOR_ELT(V,C)) -> VECTOR_SHUFFLE
This patch attempts to convert a SCALAR_TO_VECTOR using an operand from an EXTRACT_VECTOR_ELT into a VECTOR_SHUFFLE.

This prevents many cases of spilling scalar data between the gpr + simd registers. 

At present the optimization only accepts cases where there is no TRUNC of the scalar type (i.e. all types must match).

Differential Revision: http://reviews.llvm.org/D8132

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231554 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-07 05:52:42 +00:00
Eric Christopher
80d55e6bcb Remove use of misched-bench from this test and replace it with
non-temporary enabling options. This is part of removing misched-bench
as an option.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231546 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-07 01:39:06 +00:00
Eric Christopher
5dc2251b4e Recommit r231324 with a fix to the ARM execution domain code
to disable lane switching if we don't actually have the instruction
set we want to switch to. Models the earlier check above the
conditional for the pass.

The testcase is one that triggered with the assert that's added
as part of the fix, use it to avoid adding a new testcase as it
highlights the same problem.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231539 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-07 00:12:22 +00:00
Quentin Colombet
05a3f9120a [AArch64][LoadStoreOptimizer] Generate LDP + SXTW instead of LD[U]R + LD[U]RSW.
Teach the load store optimizer how to sign extend a result of a load pair when
it helps creating more pairs.
The rational is that loads are more expensive than sign extensions, so if we
gather some in one instruction this is better!

<rdar://problem/20072968>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231527 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 22:42:10 +00:00
Sanjay Patel
5bac8f9b95 fixed to test features, not CPUs
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231524 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 21:50:42 +00:00
Sanjay Patel
f528a40240 fixed to test features, not CPUs
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231523 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 21:50:27 +00:00
Sanjay Patel
5ff9d3e6ed loosen checking for buildbots
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231522 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 21:30:18 +00:00
Sanjay Patel
aedb16fc6f fixed to test only the feature, not the feature and a CPU
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231521 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 21:24:56 +00:00
Sanjay Patel
b00a131bda fixed to test only the feature, not the feature and a CPU
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231520 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 21:19:32 +00:00
Sanjay Patel
50652e746b fixed test to use FileCheck
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231519 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 21:16:15 +00:00
Sanjay Patel
6deb05e63a fixed to use CHECK-LABELs
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231517 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 21:05:02 +00:00
Sanjay Patel
d532d10275 fixed to test only the feature, not the feature and a CPU
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231516 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 20:58:15 +00:00
Sanjay Patel
f2b34a568b fixed to test only the feature, not the feature and a CPU
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231515 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 20:57:40 +00:00
Sanjay Patel
9e03e85cac fixed to test feature, not CPU
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231513 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 20:51:25 +00:00
Sanjay Patel
17392758a1 fixed to test features, not CPUs
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231512 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 20:46:16 +00:00
Sanjay Patel
91b79125ec fixed test to use SSE2 attribute
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231510 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 20:38:55 +00:00
Sanjay Patel
e7abe0cdbc fixed to test only the feature, not the feature and a CPU
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231509 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 20:34:20 +00:00
Matthias Braun
47941aa098 DAGCombiner: Canonicalize select(and/or,x,y) depending on target.
This is based on the following equivalences:
select(C0 & C1, X, Y) <=> select(C0, select(C1, X, Y), Y)
select(C0 | C1, X, Y) <=> select(C0, X, select(C1, X, Y))

Many target cannot perform and/or on the CPU flags and therefore the
right side should be choosen to avoid materializign the i1 flags in an
integer register. If the target can perform this operation efficiently
we normalize to the left form.

Differential Revision: http://reviews.llvm.org/D7622

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231507 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 19:49:10 +00:00
Michael Zolotukhin
6023ad2d37 LegalizeTypes: Handle shift by 0 in ExpandShiftByConstant.
Though such shifts are usually optimized away by combiner, we still can
encounter them after a vector shift is legalized.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231443 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-06 01:13:01 +00:00
Sanjay Patel
5f79fd2f02 [AVX] Lower / fast-isel scalar FP selects into VBLENDV instructions (PR22483)
This patch reduces code size for all AVX targets and increases speed for some chips.

SSE 4.1 introduced the useless (see code comments) 2-register form of BLENDV and
only in the packed float/double flavors.

AVX subsequently made the instruction useful by adding a 4-register operand form.

So we just need to paper over the lack of scalar forms of this instruction, complicate
the code to choose float or double forms, and use blendv on scalars since all FP is in
xmm registers anyway.

This gives us an approximately 50% speed up for a blendv microbenchmark sequence
on SandyBridge and Haswell:
blendv : 29.73 cycles/iter
logic : 43.15 cycles/iter

No new test cases with this patch because:

1. fast-isel-select-sse.ll tests the positive side for regular X86 lowering and fast-isel
2. sse-minmax.ll and fp-select-cmp-and.ll confirm that we're not firing for scalar selects without AVX
3. fp-select-cmp-and.ll and logical-load-fold.ll confirm that we're not firing for scalar selects with constants.

http://llvm.org/bugs/show_bug.cgi?id=22483

Differential Revision: http://reviews.llvm.org/D8063



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231408 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 21:46:54 +00:00
Ahmed Bougacha
77f46f4f9f [AArch64] Teach AsmPrinter about GlobalAddress operands.
Fixes PR22761, rdar://20024866.
Differential Revision: http://reviews.llvm.org/D8042


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231400 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 20:04:21 +00:00
Rafael Espindola
2f76abe7d7 Use the correct func begin symbol in all places in ppc.
I missed an occurrence of the old symbol in my previous patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231398 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 19:47:50 +00:00
Ahmed Bougacha
67297cd956 [ARM] Enable vector extload combine for legal types.
This commit enables forming vector extloads for ARM.
It only does so for legal types, and when we can't fold the extension
in a wide/long form of the user instruction.

Enabling it for larger types isn't as good an idea on ARM as it is on
X86, because: 
- we pretend that extloads are legal, but end up generating vld+vmov
- we have instructions like vld {dN, dM}, which can't be generated
  when we "manually expand" extloads to vld+vmov.

For legal types, the combine doesn't fire that often: in the
integration tests only in a big endian testcase, where it removes a
pointless AND.

Related to rdar://19723053
Differential Revision: http://reviews.llvm.org/D7423


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231396 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 19:37:53 +00:00
Rafael Espindola
2e2dbc35da Use the generic Lfunc_begin label on ppc.
This removes yet another custom label to mark the start of a function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231390 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 18:55:50 +00:00
David Majnemer
42fcf79f36 X86: Optimize address mode matching for FRAME_ALLOC_RECOVER nodes
We know that the absolute symbol will be less than 2GB and thus will
always fit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231389 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 18:50:12 +00:00
Reid Kleckner
9f7c861416 Replace llvm.frameallocate with llvm.frameescape
Turns out it's pretty straightforward and simplifies the implementation.

Reviewers: andrew.w.kaylor

Differential Revision: http://reviews.llvm.org/D8051

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231386 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 18:26:34 +00:00
Simon Pilgrim
a744a15e97 [DagCombiner] Allow shuffles to merge through bitcasts
Currently shuffles may only be combined if they are of the same type, despite the fact that bitcasts are often introduced in between shuffle nodes (e.g. x86 shuffle type widening).

This patch allows a single input shuffle to peek through bitcasts and if the input is another shuffle will merge them, shuffling using the smallest sized type, and re-applying the bitcasts at the inputs and output instead.

Dropped old ShuffleToZext test - this patch removes the use of the zext and vector-zext.ll covers these anyhow.

Differential Revision: http://reviews.llvm.org/D7939

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231380 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 17:14:04 +00:00
Kit Barton
b98636a0f8 While reviewing the changes to Clang to add builtin support for the vsld, vsrd, and vsrad instructions, it was pointed out that the builtins are generating the LLVM opcodes (shl, lshr, and ashr) not calls to the intrinsics. This patch changes the implementation of the vsld, vsrd, and vsrad instructions from from intrinsics to VXForm_1 instructions and makes them legal with P8 Altivec. It also removes the definition of the int_ppc_altivec_vsld, int_ppc_altivec_vsrd, and int_ppc_altivec_vsrad intrinsics.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231378 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 16:24:38 +00:00
Igor Laevsky
684d323b9b Revert change r231366 as it broke clang-native-arm-cortex-a9 Analysis/properties.m test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231374 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 15:41:14 +00:00
Elena Demikhovsky
e670dc7848 AVX-512, SKX: Enabled masked_load/store operations for this target.
Added lowering for ISD::CONCAT_VECTORS and ISD::INSERT_SUBVECTOR for i1 vectors,
it is needed to pass all masked_memop.ll tests for SKX.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231371 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 15:11:35 +00:00
Igor Laevsky
f8b3003ab8 Teach lowering to correctly handle invoke statepoint and gc results tied to them. Note that we still can not lower gc.relocates for invoke statepoints.
Also it extracts getCopyFromRegs helper function in SelectionDAGBuilder as we need to be able to customize type of the register exported from basic block during lowering of the gc.result.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231366 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 14:11:21 +00:00
Craig Topper
62eaac6087 [X86] Use vmovss to handle inserting an element into index 0 of a v8f32 vector of zeros.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231354 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 06:38:42 +00:00
Chandler Carruth
4197c13062 [MBP] Revert r231238 which attempted to fix a nasty bug where MBP is
just arbitrarily interleaving unrelated control flows once they get
moved "out-of-line" (both outside of natural CFG ordering and with
diamonds that cannot be fully laid out by chaining fallthrough edges).

This easy solution doesn't work in practice, and it isn't just a small
bug. It looks like a very different strategy will be required. I'm
working on that now, and it'll again go behind some flag so that
everyone can experiment and make sure it is working well for them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231332 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 01:07:03 +00:00
Matthias Braun
29aeaf5408 Improve test robustness
Improve test robustness in preparation of coming commits:
- Avoid undefs which may get propagated too much.
- Remove several pointless add 0, instructions

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231307 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 22:31:18 +00:00
Nemanja Ivanovic
b69d556c37 Add LLVM support for PPC cryptography builtins
Review: http://reviews.llvm.org/D7955


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231285 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 20:44:33 +00:00
Mehdi Amini
c94da20917 Make DataLayout Non-Optional in the Module
Summary:
DataLayout keeps the string used for its creation.

As a side effect it is no longer needed in the Module.
This is "almost" NFC, the string is no longer
canonicalized, you can't rely on two "equals" DataLayout
having the same string returned by getStringRepresentation().

Get rid of DataLayoutPass: the DataLayout is in the Module

The DataLayout is "per-module", let's enforce this by not
duplicating it more than necessary.
One more step toward non-optionality of the DataLayout in the
module.

Make DataLayout Non-Optional in the Module

Module->getDataLayout() will never returns nullptr anymore.

Reviewers: echristo

Subscribers: resistor, llvm-commits, jholewinski

Differential Revision: http://reviews.llvm.org/D7992

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231270 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 18:43:29 +00:00
Adrian Prantl
2e74ddea3a Update the out-of-date dwarf expressions in these testcases.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231261 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 17:39:59 +00:00
Marek Olsak
506d4b2cb4 R600/SI: Add an intrinsic for S_FLBIT_I32 / V_FFBH_I32
Required by OpenGL (ARB_gpu_shader5).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231259 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 17:33:45 +00:00
Jozef Kolek
2e37a6f306 [mips][microMIPS] Make usage of ADDU16 and SUBU16 by code generator
Differential Revision: http://reviews.llvm.org/D7609


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231249 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 15:47:42 +00:00
Andrea Di Biagio
da5e5688e9 [X86][FastISel] Simplify the logic in method X86SelectSIToFP.
The target-independent selection algorithm in FastISel already knows how
to select a SINT_TO_FP if the target is SSE but not AVX.

On targets that have SSE but not AVX, the tablegen'd 'fastEmit' functions
for ISD::SINT_TO_FP know how to select instruction X86::CVTSI2SSrr
(for an i32 to f32 conversion) and X86::CVTSI2SDrr (for an i32 to f64
conversion).

This patch simplifies the logic in method X86SelectSIToFP knowing that
the code would not be reachable if the subtarget doesn't have AVX.
No functional change intended.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231243 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 14:23:25 +00:00
Chandler Carruth
67fade9110 [MBP] Fix a really horrible bug in MachineBlockPlacement, but behind
a flag for now.

First off, thanks to Daniel Jasper for really pointing out the issue
here. It's been here forever (at least, I think it was there when
I first wrote this code) without getting really noticed or fixed.

The key problem is what happens when two reasonably common patterns
happen at the same time: we outline multiple cold regions of code, and
those regions in turn have diamonds or other CFGs for which we can't
just topologically lay them out. Consider some C code that looks like:

  if (a1()) { if (b1()) c1(); else d1(); f1(); }
  if (a2()) { if (b2()) c2(); else d2(); f2(); }
  done();

Now consider the case where a1() and a2() are unlikely to be true. In
that case, we might lay out the first part of the function like:

  a1, a2, done;

And then we will be out of successors in which to build the chain. We go
to find the best block to continue the chain with, which is perfectly
reasonable here, and find "b1" let's say. Laying out successors gets us
to:

  a1, a2, done; b1, c1;

At this point, we will refuse to lay out the successor to c1 (f1)
because there are still un-placed predecessors of f1 and we want to try
to preserve the CFG structure. So we go get the next best block, d1.

... wait for it ...

Except that the next best block *isn't* d1. It is b2! d1 is waaay down
inside these conditionals. It is much less important than b2. Except
that this is exactly what we didn't want. If we keep going we get the
entire set of the rest of the CFG *interleaved*!!!

  a1, a2, done; b1, c1; b2, c2; d1, f1; d2, f2;

So we clearly need a better strategy here. =] My current favorite
strategy is to actually try to place the block whose predecessor is
closest. This very simply ensures that we unwind these kinds of CFGs the
way that is natural and fitting, and should minimize the number of cache
lines instructions are spread across.

It also happens to be *dead simple*. It's like the datastructure was
specifically set up for this use case or something. We only push blocks
onto the work list when the last predecessor for them is placed into the
chain. So the back of the worklist *is* the nearest next block.

Unfortunately, a change like this is going to cause *soooo* many
benchmarks to swing wildly. So for now I'm adding this under a flag so
that we and others can validate that this is fixing the problems
described, that it seems possible to enable, and hopefully that it fixes
more of our problems long term.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231238 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 12:18:08 +00:00