5935 Commits

Author SHA1 Message Date
Hans Wennborg
ba6d2568f9 Switch lowering: order bit tests by branch weight.
llvm-svn: 235912
2015-04-27 20:21:17 +00:00
Elena Demikhovsky
a480ef5494 AVX-512: added calling conventions for i1 vectors.
Fixed bug: https://llvm.org/bugs/show_bug.cgi?id=20724

llvm-svn: 235889
2015-04-27 15:11:19 +00:00
Elena Demikhovsky
d1084c5b3f AVX-512: Extend/Truncate operations for SKX,
SETCC for bit-vectors

llvm-svn: 235875
2015-04-27 12:57:59 +00:00
Simon Pilgrim
4f683c264a [X86][SSE] Add v16i8/v32i8 multiplication support
Patch to allow int8 vectors to be multiplied on the SSE unit instead of being scalarized.

The patch sign extends the i8 lanes to i16, uses the SSE2 pmullw multiplication instruction, then packs the lower byte from each result.

Differential Revision: http://reviews.llvm.org/D9115

llvm-svn: 235837
2015-04-27 07:55:46 +00:00
Sanjay Patel
3eb5146b3c add SSE run to check non-AVX codegen
llvm-svn: 235809
2015-04-25 20:41:51 +00:00
Simon Pilgrim
aedd3c5160 line endings fix
llvm-svn: 235800
2015-04-25 12:12:43 +00:00
Reid Kleckner
cfbfe6f29c [SEH] Implement GetExceptionCode in __except blocks
This introduces an intrinsic called llvm.eh.exceptioncode. It is lowered
by copying the EAX value live into whatever basic block it is called
from. Obviously, this only works if you insert it late during codegen,
because otherwise mid-level passes might reschedule it.

llvm-svn: 235768
2015-04-24 20:25:05 +00:00
David Blaikie
445e3fbc54 [opaque pointer type] Add textual IR support for explicit type parameter to the invoke instruction
Same as r235145 for the call instruction - the justification, tradeoffs,
etc are all the same. The conversion script worked the same without any
false negatives (after replacing 'call' with 'invoke').

llvm-svn: 235755
2015-04-24 19:32:54 +00:00
Hans Wennborg
ec679a8b3b Switch lowering: fix APInt overflow causing infinite loop / OOM
llvm-svn: 235729
2015-04-24 16:53:55 +00:00
Reid Kleckner
5c5facc2ce Re-commit "[SEH] Remove the old __C_specific_handler code now that WinEHPrepare works"
This reverts commit r235617.

r235649 should have addressed the problems.

llvm-svn: 235667
2015-04-23 23:22:33 +00:00
Andrew Kaylor
20ae2a311f [WinEH] Ignore filter clauses while mapping landing pad blocks.
llvm-svn: 235656
2015-04-23 22:38:36 +00:00
Quentin Colombet
796d906e06 [MachineCopyPropagation] Handle undef flags conservatively so that we do not
remove copies that are useful after breaking some hardware dependencies.
In other words, handle this kind of situations conservatively by assuming reg2
is redefined by the undef flag.
reg1 = copy reg2
= inst reg2<undef>
reg2 = copy reg1
Copy propagation used to remove the last copy.
This is incorrect because the undef flag on reg2 in inst, allows next
passes to put whatever trashed value in reg2 that may help.
In practice we end up with this code:
reg1 = copy reg2
reg2 = 0
= inst reg2<undef>
reg2 = copy reg1

This fixes PR21743.

llvm-svn: 235647
2015-04-23 21:17:39 +00:00
Reid Kleckner
909ea7e6b8 Revert "[SEH] Remove the old __C_specific_handler code now that WinEHPrepare works"
We still have some "uses remain after removal" issues in -O0 builds.

This reverts commit r235557.

llvm-svn: 235617
2015-04-23 18:34:01 +00:00
Hans Wennborg
0867b151c9 Re-commit r235560: Switch lowering: extract jump tables and bit tests before building binary tree (PR22262)
Third time's the charm. The previous commit was reverted as a
reverse for-loop in SelectionDAGBuilder::lowerWorkItem did 'I--'
on an iterator at the beginning of a vector, causing asserts
when using debugging iterators. This commit fixes that.

llvm-svn: 235608
2015-04-23 16:45:24 +00:00
Sanjay Patel
f4b0f07430 use update_llc_test_checks.py to tighten checking; remove unnecessary CPU param
llvm-svn: 235604
2015-04-23 16:07:50 +00:00
Aaron Ballman
0be238cebd Revert r235560; this commit was causing several failed assertions in Debug builds using MSVC's STL. The iterator is being used outside of its valid range.
llvm-svn: 235597
2015-04-23 13:41:59 +00:00
Simon Pilgrim
86b034bae9 [DAGCombiner] Remove extra bitcasts surrounding vector shuffles
Patch to remove extra bitcasts from shuffles, this is often a legacy of XformToShuffleWithZero being used to combine bitmaskings (of float vectors bitcast to integer vectors) into shuffles: bitcast(shuffle(bitcast(s0),bitcast(s1))) -> shuffle(s0,s1)

Differential Revision: http://reviews.llvm.org/D9097

llvm-svn: 235578
2015-04-23 08:43:13 +00:00
Andrew Kaylor
86e67f7ebc [WinEH] Removing seh-filter.ll until I can determine its validity
llvm-svn: 235566
2015-04-23 00:38:22 +00:00
Hans Wennborg
15823d49b6 Switch lowering: extract jump tables and bit tests before building binary tree (PR22262)
This is a re-commit of r235101, which also fixes the problems with the previous patch:

- Switches with only a default case and non-fallthrough were handled incorrectly

- The previous patch tickled a bug in PowerPC Early-Return Creation which is fixed here.

> This is a major rewrite of the SelectionDAG switch lowering. The previous code
> would lower switches as a binary tre, discovering clusters of cases
> suitable for lowering by jump tables or bit tests as it went along. To increase
> the likelihood of finding jump tables, the binary tree pivot was selected to
> maximize case density on both sides of the pivot.
>
> By not selecting the pivot in the middle, the binary trees would not always
> be balanced, leading to performance problems in the generated code.
>
> This patch rewrites the lowering to search for clusters of cases
> suitable for jump tables or bit tests first, and then builds the binary
> tree around those clusters. This way, the binary tree will always be balanced.
>
> This has the added benefit of decoupling the different aspects of the lowering:
> tree building and jump table or bit tests finding are now easier to tweak
> separately.
>
> For example, this will enable us to balance the tree based on profile info
> in the future.
>
> The algorithm for finding jump tables is quadratic, whereas the previous algorithm
> was O(n log n) for common cases, and quadratic only in the worst-case. This
> doesn't seem to be major problem in practice, e.g. compiling a file consisting
> of a 10k-case switch was only 30% slower, and such large switches should be rare
> in practice. Compiling e.g. gcc.c showed no compile-time difference.  If this
> does turn out to be a problem, we could limit the search space of the algorithm.
>
> This commit also disables all optimizations during switch lowering in -O0.
>
> Differential Revision: http://reviews.llvm.org/D8649

llvm-svn: 235560
2015-04-22 23:14:56 +00:00
Reid Kleckner
64a2a6a473 [SEH] Remove the old __C_specific_handler code now that WinEHPrepare works
This removes the -sehprepare flag and makes __C_specific_handler
functions always to use WinEHPrepare.

This was tested by building all of chromium_builder_tests and running a
few tests that use SEH, but if something breaks, we can revert this.

llvm-svn: 235557
2015-04-22 22:13:09 +00:00
Sanjay Patel
cab567873f [x86] Add store-folded memop patterns for vcvtps2ph
Differential Revision: http://reviews.llvm.org/D7296

llvm-svn: 235517
2015-04-22 16:11:19 +00:00
Andrea Di Biagio
6cd2f42fac [X86][AVX] Fix failure due to a missing ISel pattern to select VBROADCAST nodes (PR23259).
This fixes a regression introduced at revision 218263.

On AVX, if we optimize for size, a splat build_vector of a load
is lowered into a VBROADCAST node. This is done even if the value type of the
splat build_vector node is v2i64.

Since AVX doesn't support v2f64/v2i64 broadcasts, revision 218263 added two
extra tablegen patterns to allow selecting a VMOVDDUPrm from an X86VBroadcast
where the scalar element comes from a loadi64/loadf64.

However, revision 218263 forgot to add an extra fallback pattern for the case
where we have a X86VBroadcast of a loadi64 with multiple uses.

This patch adds the missing tablegen pattern in X86InstrSSE.td.
This patch also adds an extra test to 'splat-for-size.ll' to verify that ISel
doesn't crash with a 'fatal error in the backend' due to a missing AVX pattern
to select v2i64 X86ISD::BROADCAST nodes.

llvm-svn: 235509
2015-04-22 14:53:39 +00:00
Lang Hames
65613a634a [patchpoint] Add support for symbolic patchpoint targets to SelectionDAG and the
X86 backend.

The code generated for symbolic targets is identical to the code generated for
constant targets, except that a relocation is emitted to fix up the actual
target address at link-time. This allows IR and object files containing
patchpoints to be cached across JIT-invocations where the target address may
change.

llvm-svn: 235483
2015-04-22 06:02:31 +00:00
Sanjay Patel
fe1365ac50 [x86] allow 64-bit extracted vector element integer stores on a 32-bit system
With SSE2, we can generate a 'movq' or other 64-bit store op on a 32-bit system
even though 64-bit integers are not legal types.

So instead of producing this:

  pshufd	$229, %xmm0, %xmm1      ## xmm1 = xmm0[1,1,2,3]
  movd	%xmm0, (%eax)
  movd	%xmm1, 4(%eax)

We can do:

  movq %xmm0, (%eax)

This is a fix for the problem noted in D7296.

Differential Revision: http://reviews.llvm.org/D9134

llvm-svn: 235460
2015-04-22 00:24:30 +00:00
Reid Kleckner
d2a1a51996 Re-land r235154-r235156 under the existing -sehprepare flag
Keep the old SEH fan-in lowering on by default for now, since projects
rely on it.  This will make it easy to test this change with a simple
flag flip.

llvm-svn: 235399
2015-04-21 18:23:57 +00:00
Matthias Braun
9e9e8b3230 X86: Match for X86ISD nodes in LowerBUILD_VECTOR instead of BUILD_VECTORCombine
There doesn't seem to be a reason to perform this target ISD node matching
in an DAGCombine, moving it to lowering fixes PR23296.

Differential Revision: http://reviews.llvm.org/D9137

llvm-svn: 235394
2015-04-21 17:21:36 +00:00
Elena Demikhovsky
50b88ddb87 AVX-512: Added logical and arithmetic instructions for SKX
by Asaf Badouh (asaf.badouh@intel.com)

llvm-svn: 235375
2015-04-21 10:27:40 +00:00
Simon Pilgrim
398ce22b86 [X86][SSE] Provide execution domains for scalar floating point operations
This is an updated version of Chandler's patch D7402 that got accepted but never committed, and has bit-rotted a bit since.

I've updated the execution domain declarations to match the approach of the packed templates and also added some extra scalar unary tests.

Differential Revision: http://reviews.llvm.org/D9095

llvm-svn: 235372
2015-04-21 08:40:22 +00:00
Simon Pilgrim
860f08779c CONCAT_VECTOR of BUILD_VECTOR - minor fix
Fixed issue with the combine of CONCAT_VECTOR of 2 BUILD_VECTOR nodes - the optimisation wasn't ensuring that the scalar operands of both nodes were the same type/size for implicit truncation.

Test case spotted by Patrik Hagglund

llvm-svn: 235371
2015-04-21 08:05:43 +00:00
Pawel Bylica
57c2f7c756 Fix generic shift expansion when shift amount is 0
Summary:
This fixes http://llvm.org/bugs/show_bug.cgi?id=16439. 

This is one possible way to approach this. The other would be to split InL>>(nbits-Amt) into (InL>>(nbits-1-Amt))>>1, which is also valid since since we only need to care about Amt up nbits-1. It's hard to tell which one is better since the shift might be expensive if this stage of expansion is not yet a legal machine integer, whereas comparisons with zero are relatively cheap at all sizes, but more expensive than a shift if the shift is on a legal machine type. 

Patch by Keno Fischer!

Test Plan: regression test from http://reviews.llvm.org/D7752

Reviewers: chfast, resistor

Reviewed By: chfast, resistor

Subscribers: sanjoy, resistor, chfast, llvm-commits

Differential Revision: http://reviews.llvm.org/D4978

llvm-svn: 235370
2015-04-21 06:28:36 +00:00
Matthias Braun
b6b5aaad98 X86: Do not select X86 custom vector nodes if operand types don't match
X86ISD::ADDSUB, X86ISD::(F)HADD, X86ISD::(F)HSUB should not be selected
if the operand types do not match the result type because vector type
legalization cannot deal with this for custom nodes.

Testcase X86ISD::ADDSUB is attached. I could not create a testcase for
the FHADD/FHSUB cases because of: https://llvm.org/bugs/show_bug.cgi?id=23296

Differential Revision: http://reviews.llvm.org/D9120

llvm-svn: 235367
2015-04-21 01:13:41 +00:00
Sanjay Patel
362f89cd46 use update_llc_test_checks.py to tighten checking
Also, replace win and linux runs with a generic run because that
makes no difference in what this test is checking.

llvm-svn: 235361
2015-04-20 23:31:53 +00:00
Andrea Di Biagio
98c367093d [X86][FastIsel] Fix assertion failure when selecting int-to-double conversion (PR23273).
This fixes a regression introduced at revision 231243.
The target-independent selection algorithm in FastISel knows how to select
a SINT_TO_FP if the target is SSE but not AVX. That is because on X86, the
tablegen'd 'fastEmit' functions know how to select CVTSI2SSrr and CVTSI2SDrr.

Method X86FastISel::X86SelectSIToFP was therefore working under the
wrong assumption that the target was AVX. That assumption was incorrect since
we can have a target that is neither AVX nor SSE.

So, rather than asserting for the presence of AVX, we should have had an
early exit from 'X86SelectSIToFP' if the target was not AVX.
This patch fixes the issue replacing the invalid assertion with an early exit.

Thanks to Dimitry Andric for reporting this problem and for providing a small
reproducible testcase. Added test pr23273.ll.

llvm-svn: 235295
2015-04-20 11:56:59 +00:00
Simon Pilgrim
749953eebb [X86][SSE] Fix for getScalarValueForVectorElement to detect scalar sources requiring truncation.
The fix ensures that scalar sources inserted into a vector are the correct bit size.

Integer scalar sources from BUILD_VECTOR and SCALAR_TO_VECTOR nodes may require truncation that this function doesn't currently support.

llvm-svn: 235281
2015-04-19 22:16:49 +00:00
Simon Pilgrim
4c107b5258 [X86][SSE] Extended copysign tests to include llvm intrinsic implementation and constant folding.
llvm-svn: 235279
2015-04-19 21:34:57 +00:00
Simon Pilgrim
6292d50eda [X86][AVX2] Force execution domain on broadcast folding tests.
llvm-svn: 235260
2015-04-18 21:24:16 +00:00
Simon Pilgrim
e68c8606ed [X86][SSE] Force execution domain on float/double unpack shuffle tests.
llvm-svn: 235259
2015-04-18 18:50:55 +00:00
Sanjay Patel
2161c49a4e [X86, AVX] add an exedepfix entry for vmovq == vmovlps == vmovlpd
This is the AVX extension of r235014:
http://llvm.org/viewvc/llvm-project?view=revision&revision=235014

Review:
http://reviews.llvm.org/D8691

llvm-svn: 235210
2015-04-17 17:02:37 +00:00
Nico Weber
a762fa6c98 Revert r235154-r235156, they cause asserts when building win64 code (http://crbug.com/477988)
llvm-svn: 235170
2015-04-17 09:10:43 +00:00
Reid Kleckner
56cc879ac1 Fix test failure due to racing commits
It looks like r235145 changed the .ll syntax for variadic calls. Update
tests to use the new syntax.

llvm-svn: 235156
2015-04-17 01:09:53 +00:00
Reid Kleckner
d4523e3c51 [SEH] Reimplement x64 SEH using WinEHPrepare
This now emits simple, unoptimized xdata tables for __C_specific_handler
based on the handlers listed in @llvm.eh.actions calls produced by
WinEHPrepare.

This adds support for running __finally blocks when exceptions are
thrown, and removes the old landingpad fan-in codepath.

I ran some manual execution tests on small basic test cases with and
without optimization, as well as on Chrome base_unittests, which uses a
small amount of SEH.  I'm sure there are bugs, and we may need to
revert.

llvm-svn: 235154
2015-04-17 01:01:27 +00:00
David Blaikie
23af64846f [opaque pointer type] Add textual IR support for explicit type parameter to the call instruction
See r230786 and r230794 for similar changes to gep and load
respectively.

Call is a bit different because it often doesn't have a single explicit
type - usually the type is deduced from the arguments, and just the
return type is explicit. In those cases there's no need to change the
IR.

When that's not the case, the IR usually contains the pointer type of
the first operand - but since typed pointers are going away, that
representation is insufficient so I'm just stripping the "pointerness"
of the explicit type away.

This does make the IR a bit weird - it /sort of/ reads like the type of
the first operand: "call void () %x(" but %x is actually of type "void
()*" and will eventually be just of type "ptr". But this seems not too
bad and I don't think it would benefit from repeating the type
("void (), void () * %x(" and then eventually "void (), ptr %x(") as has
been done with gep and load.

This also has a side benefit: since the explicit type is no longer a
pointer, there's no ambiguity between an explicit type and a function
that returns a function pointer. Previously this case needed an explicit
type (eg: a function returning a void() function was written as
"call void () () * @x(" rather than "call void () * @x(" because of the
ambiguity between a function returning a pointer to a void() function
and a function returning void).

No ambiguity means even function pointer return types can just be
written alone, without writing the whole function's type.

This leaves /only/ the varargs case where the explicit type is required.

Given the special type syntax in call instructions, the regex-fu used
for migration was a bit more involved in its own unique way (as every
one of these is) so here it is. Use it in conjunction with the apply.sh
script and associated find/xargs commands I've provided in rr230786 to
migrate your out of tree tests. Do let me know if any of this doesn't
cover your cases & we can iterate on a more general script/regexes to
help others with out of tree tests.

About 9 test cases couldn't be automatically migrated - half of those
were functions returning function pointers, where I just had to manually
delete the function argument types now that we didn't need an explicit
function type there. The other half were typedefs of function types used
in calls - just had to manually drop the * from those.

import fileinput
import sys
import re

pat = re.compile(r'((?:=|:|^|\s)call\s(?:[^@]*?))(\s*$|\s*(?:(?:\[\[[a-zA-Z0-9_]+\]\]|[@%](?:(")?[\\\?@a-zA-Z0-9_.]*?(?(3)"|)|{{.*}}))(?:\(|$)|undef|inttoptr|bitcast|null|asm).*$)')
addrspace_end = re.compile(r"addrspace\(\d+\)\s*\*$")
func_end = re.compile("(?:void.*|\)\s*)\*$")

def conv(match, line):
  if not match or re.search(addrspace_end, match.group(1)) or not re.search(func_end, match.group(1)):
    return line
  return line[:match.start()] + match.group(1)[:match.group(1).rfind('*')].rstrip() + match.group(2) + line[match.end():]

for line in sys.stdin:
  sys.stdout.write(conv(re.search(pat, line), line))

llvm-svn: 235145
2015-04-16 23:24:18 +00:00
Hans Wennborg
a9e2057416 Revert the switch lowering change (r235101, r235103, r235106)
Looks like it broke the sanitizer-ppc64-linux1 build. Reverting for now.

llvm-svn: 235108
2015-04-16 15:43:26 +00:00
Hans Wennborg
feaf512839 Add a triple to switch.ll test.
llvm-svn: 235103
2015-04-16 15:09:33 +00:00
Hans Wennborg
d403664ed8 Switch lowering: extract jump tables and bit tests before building binary tree (PR22262)
This is a major rewrite of the SelectionDAG switch lowering. The previous code
would lower switches as a binary tre, discovering clusters of cases
suitable for lowering by jump tables or bit tests as it went along. To increase
the likelihood of finding jump tables, the binary tree pivot was selected to
maximize case density on both sides of the pivot.

By not selecting the pivot in the middle, the binary trees would not always
be balanced, leading to performance problems in the generated code.

This patch rewrites the lowering to search for clusters of cases
suitable for jump tables or bit tests first, and then builds the binary
tree around those clusters. This way, the binary tree will always be balanced.

This has the added benefit of decoupling the different aspects of the lowering:
tree building and jump table or bit tests finding are now easier to tweak
separately.

For example, this will enable us to balance the tree based on profile info
in the future.

The algorithm for finding jump tables is O(n^2), whereas the previous algorithm
was O(n log n) for common cases, and quadratic only in the worst-case. This
doesn't seem to be major problem in practice, e.g. compiling a file consisting
of a 10k-case switch was only 30% slower, and such large switches should be rare
in practice. Compiling e.g. gcc.c showed no compile-time difference.  If this
does turn out to be a problem, we could limit the search space of the algorithm.

This commit also disables all optimizations during switch lowering in -O0.

Differential Revision: http://reviews.llvm.org/D8649

llvm-svn: 235101
2015-04-16 14:49:23 +00:00
Ahmed Bougacha
c984b90c86 [CodeGen] Re-apply r234809 (concat of scalars), with an x86_mmx fix.
The only type that isn't an integer, isn't floating point, and isn't
a vector; ladies and gentlemen, the gift that keeps on giving: x86_mmx!

Fixes PR23246.

Original message (reverted in r235062):
[CodeGen] Combine concat_vectors of scalars into build_vector.

Combine something like:
  (v8i8 concat_vectors (v2i8 bitcast (i16)) x4)
into:
  (v8i8 (bitcast (v4i16 BUILD_VECTOR (i16) x4)))

If any of the scalars are floating point, use that throughout.

Differential Revision: http://reviews.llvm.org/D8948

llvm-svn: 235072
2015-04-16 02:39:14 +00:00
Duncan P. N. Exon Smith
62e0f454a0 DebugInfo: Remove 'inlinedAt:' field from MDLocalVariable
Remove 'inlinedAt:' from MDLocalVariable.  Besides saving some memory
(variables with it seem to be single largest `Metadata` contributer to
memory usage right now in -g -flto builds), this stops optimization and
backend passes from having to change local variables.

The 'inlinedAt:' field was used by the backend in two ways:

 1. To tell the backend whether and into what a variable was inlined.
 2. To create a unique id for each inlined variable.

Instead, rely on the 'inlinedAt:' field of the intrinsic's `!dbg`
attachment, and change the DWARF backend to use a typedef called
`InlinedVariable` which is `std::pair<MDLocalVariable*, MDLocation*>`.
This `DebugLoc` is already passed reliably through the backend (as
verified by r234021).

This commit removes the check from r234021, but I added a new check
(that will survive) in r235048, and changed the `DIBuilder` API in
r235041 to require a `!dbg` attachment whose 'scope:` is in the same
`MDSubprogram` as the variable's.

If this breaks your out-of-tree testcases, perhaps the script I used
(mdlocalvariable-drop-inlinedat.sh) will help; I'll attach it to PR22778
in a moment.

llvm-svn: 235050
2015-04-15 22:29:27 +00:00
Duncan P. N. Exon Smith
48b3503c16 DebugInfo: Add missing !dbg attachments to intrinsics
Add missing `!dbg` attachments to `@llvm.dbg.*` intrinsics.  I updated
these using a script (add-dbg-to-intrinsics.sh) that I'll attach to
PR22778 for posterity.

llvm-svn: 235040
2015-04-15 21:04:10 +00:00
Sanjay Patel
c03d93baa0 [X86] add an exedepfix entry for movq == movlps == movlpd
This is a 1-line patch (with a TODO for AVX because that will affect
even more regression tests) that lets us substitute the appropriate
64-bit store for the float/double/int domains.

It's not clear to me exactly what the difference is between the 0xD6 (MOVPQI2QImr) and 
0x7E (MOVSDto64mr) opcodes, but this is apparently the right choice.

Differential Revision: http://reviews.llvm.org/D8691

llvm-svn: 235014
2015-04-15 15:47:51 +00:00
Sanjay Patel
7024b8121a [x86] Implement combineRepeatedFPDivisors
Set the transform bar at 2 divisions because the fastest current
x86 FP divider circuit is in SandyBridge / Haswell at 10 cycle
latency (best case) relative to a 5 cycle multiplier. 
So that's the worst case for this transform (no latency win), 
but multiplies are obviously pipelined while divisions are not,
so there's still a big throughput win which we would expect to
show up in typical FP code.

These are the sequences I'm comparing:

  divss   %xmm2, %xmm0
  mulss   %xmm1, %xmm0
  divss   %xmm2, %xmm0

Becomes:

  movss   LCPI0_0(%rip), %xmm3    ## xmm3 = mem[0],zero,zero,zero
  divss   %xmm2, %xmm3
  mulss   %xmm3, %xmm0
  mulss   %xmm1, %xmm0
  mulss   %xmm3, %xmm0

[Ignore for the moment that we don't optimize the chain of 3 multiplies
into 2 independent fmuls followed by 1 dependent fmul...this is the DAG
version of: https://llvm.org/bugs/show_bug.cgi?id=21768 ...if we fix that,
then the transform becomes even more profitable on all targets.]

Differential Revision: http://reviews.llvm.org/D8941

llvm-svn: 235012
2015-04-15 15:22:55 +00:00