Commit Graph

184 Commits

Author SHA1 Message Date
Matt Arsenault d8ed207a20 AMDGPU: Constant fold rcp node
When doing arcp optimization with a constant denominator,
this was leaving behind rcps with constant inputs.

llvm-svn: 297248
2017-03-08 00:48:46 +00:00
Matt Arsenault eb522e68bc AMDGPU: Support v2i16/v2f16 packed operations
llvm-svn: 296396
2017-02-27 22:15:25 +00:00
Wei Ding 4d3d4ca1b3 AMDGPU : Replace FMAD with FMA when denormals are enabled.
Differential Revision: http://reviews.llvm.org/D29958

llvm-svn: 296186
2017-02-24 23:00:29 +00:00
Matt Arsenault 1f17c66890 AMDGPU: Add cvt.pkrtz intrinsic
Convert llvm.SI.packf16 test uses

llvm-svn: 295797
2017-02-22 00:27:34 +00:00
Matt Arsenault 9417505f7d AMDGPU: Remove llvm.AMDGPU.clamp intrinsic
llvm-svn: 295789
2017-02-21 23:46:04 +00:00
Matt Arsenault 2fdf2a1a18 AMDGPU: Redefine clamp node as clamp 0.0-1.0
Change implementation to use max instead of add.
min/max/med3 do not flush denormals regardless of the mode,
so it is OK to use it whether or not they are enabled.

Also allow using clamp with f16, and use knowledge
of dx10_clamp.

llvm-svn: 295788
2017-02-21 23:35:48 +00:00
Matt Arsenault 0699ef39ce AMDGPU: Add pass to expand memcpy/memmove/memset
llvm-svn: 294635
2017-02-09 22:00:42 +00:00
Matt Arsenault e1b595306d AMDGPU: Fold fneg into fmin/fmax_legacy
llvm-svn: 293972
2017-02-03 00:51:50 +00:00
Matt Arsenault 2511c031de AMDGPU: Fold fneg into fminnum/fmaxnum
llvm-svn: 293968
2017-02-03 00:23:15 +00:00
Matt Arsenault a8fcfadf46 AMDGPU: Check if users of fneg can fold mods
In multi-use cases this can save a few instructions.

llvm-svn: 293962
2017-02-02 23:21:23 +00:00
Nirav Dave 93f9d5ce04 Revert "In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled."
This reverts commit r293893 which is miscompiling lua on ARM and
bootstrapping for x86-windows.

llvm-svn: 293915
2017-02-02 18:24:55 +00:00
Nirav Dave 4442667fc5 In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled.
Recommiting after fixing X86 inc/dec chain bug.

    * Simplify Consecutive Merge Store Candidate Search

    Now that address aliasing is much less conservative, push through
    simplified store merging search and chain alias analysis which only
    checks for parallel stores through the chain subgraph. This is cleaner
    as the separation of non-interfering loads/stores from the
    store-merging logic.

    When merging stores search up the chain through a single load, and
    finds all possible stores by looking down from through a load and a
    TokenFactor to all stores visited.

    This improves the quality of the output SelectionDAG and the output
    Codegen (save perhaps for some ARM cases where we correctly constructs
    wider loads, but then promotes them to float operations which appear
    but requires more expensive constant generation).

    Some minor peephole optimizations to deal with improved SubDAG shapes (listed below)

    Additional Minor Changes:

      1. Finishes removing unused AliasLoad code

      2. Unifies the chain aggregation in the merged stores across code
         paths

      3. Re-add the Store node to the worklist after calling
         SimplifyDemandedBits.

      4. Increase GatherAllAliasesMaxDepth from 6 to 18. That number is
         arbitrary, but seems sufficient to not cause regressions in
         tests.

      5. Remove Chain dependencies of Memory operations on CopyfromReg
         nodes as these are captured by data dependence

      6. Forward loads-store values through tokenfactors containing
          {CopyToReg,CopyFromReg} Values.

      7. Peephole to convert buildvector of extract_vector_elt to
         extract_subvector if possible (see
         CodeGen/AArch64/store-merge.ll)

      8. Store merging for the ARM target is restricted to 32-bit as
         some in some contexts invalid 64-bit operations are being
         generated. This can be removed once appropriate checks are
         added.

    This finishes the change Matt Arsenault started in r246307 and
    jyknight's original patch.

    Many tests required some changes as memory operations are now
    reorderable, improving load-store forwarding. One test in
    particular is worth noting:

      CodeGen/PowerPC/ppc64-align-long-double.ll - Improved load-store
      forwarding converts a load-store pair into a parallel store and
      a memory-realized bitcast of the same value. However, because we
      lose the sharing of the explicit and implicit store values we
      must create another local store. A similar transformation
      happens before SelectionDAG as well.

    Reviewers: arsenm, hfinkel, tstellarAMD, jyknight, nhaehnle

llvm-svn: 293893
2017-02-02 14:39:42 +00:00
Matt Arsenault 9dba9bd4cf AMDGPU: Use source modifiers with f16->f32 conversions
The operand types were defined to fit the fp16_to_fp node, which
has the half as an integer type. v_cvt_f32_f16 does support
source modifiers, so change this to have an FP type and modifiers.

For targets without legal f16, this requires recognizing the
bit operations and trying to produce them.

llvm-svn: 293857
2017-02-02 02:27:04 +00:00
Matt Arsenault da7a656542 AMDGPU: Cleanup fmin/fmax legacy function
Use a more specific subtarget check and combine hasOneUse checks

llvm-svn: 293726
2017-02-01 00:42:40 +00:00
Tom Stellard ca16621b2a Re-commit AMDGPU/GlobalISel: Add support for simple shaders
Fix build when global-isel is disabled and fix a warning.

Summary: We can select constant/global G_LOAD, global G_STORE, and G_GEP.

Reviewers: qcolombet, MatzeB, t.p.northover, ab, arsenm

Subscribers: mehdi_amini, vkalintiris, kzhuravl, wdng, nhaehnle, mgorny, yaxunl, tony-tye, modocache, llvm-commits, dberris

Differential Revision: https://reviews.llvm.org/D26730

llvm-svn: 293551
2017-01-30 21:56:46 +00:00
Tom Stellard 7a19d56f73 Revert "AMDGPU/GlobalISel: Add support for simple shaders"
This reverts commit r293503.

Revert while I investigate some of the buildbot failures.

llvm-svn: 293509
2017-01-30 17:42:41 +00:00
Tom Stellard e48f60aec8 AMDGPU/GlobalISel: Add support for simple shaders
Summary: We can select constant/global G_LOAD, global G_STORE, and G_GEP.

Reviewers: qcolombet, MatzeB, t.p.northover, ab, arsenm

Subscribers: mehdi_amini, vkalintiris, kzhuravl, wdng, nhaehnle, mgorny, yaxunl, tony-tye, modocache, llvm-commits, dberris

Differential Revision: https://reviews.llvm.org/D26730

llvm-svn: 293503
2017-01-30 17:09:15 +00:00
Matthias Braun 8c209aa877 Cleanup dump() functions.
We had various variants of defining dump() functions in LLVM. Normalize
them (this should just consistently implement the things discussed in
http://lists.llvm.org/pipermail/cfe-dev/2014-January/034323.html

For reference:
- Public headers should just declare the dump() method but not use
  LLVM_DUMP_METHOD or #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
- The definition of a dump method should look like this:
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  LLVM_DUMP_METHOD void MyClass::dump() {
    // print stuff to dbgs()...
  }
  #endif

llvm-svn: 293359
2017-01-28 02:02:38 +00:00
Nirav Dave d32a421f75 Revert "In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled."
This reverts commit r293184 which is failing in LTO builds

llvm-svn: 293188
2017-01-26 16:46:13 +00:00
Nirav Dave de6516c466 In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled.
* Simplify Consecutive Merge Store Candidate Search

    Now that address aliasing is much less conservative, push through
    simplified store merging search and chain alias analysis which only
    checks for parallel stores through the chain subgraph. This is cleaner
    as the separation of non-interfering loads/stores from the
    store-merging logic.

    When merging stores search up the chain through a single load, and
    finds all possible stores by looking down from through a load and a
    TokenFactor to all stores visited.

    This improves the quality of the output SelectionDAG and the output
    Codegen (save perhaps for some ARM cases where we correctly constructs
    wider loads, but then promotes them to float operations which appear
    but requires more expensive constant generation).

    Some minor peephole optimizations to deal with improved SubDAG shapes (listed below)

    Additional Minor Changes:

      1. Finishes removing unused AliasLoad code

      2. Unifies the chain aggregation in the merged stores across code
         paths

      3. Re-add the Store node to the worklist after calling
         SimplifyDemandedBits.

      4. Increase GatherAllAliasesMaxDepth from 6 to 18. That number is
         arbitrary, but seems sufficient to not cause regressions in
         tests.

      5. Remove Chain dependencies of Memory operations on CopyfromReg
         nodes as these are captured by data dependence

      6. Forward loads-store values through tokenfactors containing
          {CopyToReg,CopyFromReg} Values.

      7. Peephole to convert buildvector of extract_vector_elt to
         extract_subvector if possible (see
         CodeGen/AArch64/store-merge.ll)

      8. Store merging for the ARM target is restricted to 32-bit as
         some in some contexts invalid 64-bit operations are being
         generated. This can be removed once appropriate checks are
         added.

    This finishes the change Matt Arsenault started in r246307 and
    jyknight's original patch.

    Many tests required some changes as memory operations are now
    reorderable, improving load-store forwarding. One test in
    particular is worth noting:

      CodeGen/PowerPC/ppc64-align-long-double.ll - Improved load-store
      forwarding converts a load-store pair into a parallel store and
      a memory-realized bitcast of the same value. However, because we
      lose the sharing of the explicit and implicit store values we
      must create another local store. A similar transformation
      happens before SelectionDAG as well.

    Reviewers: arsenm, hfinkel, tstellarAMD, jyknight, nhaehnle

llvm-svn: 293184
2017-01-26 16:02:24 +00:00
Matt Arsenault 53f0cc238c AMDGPU: Fold fneg into round instructions
llvm-svn: 293127
2017-01-26 01:25:36 +00:00
Matt Arsenault 7b49ad74ed AMDGPU: Propagate fast math flags in fneg combines
Can't for fma/mad since it seems they can't have flags currently.

llvm-svn: 292818
2017-01-23 19:08:34 +00:00
Jan Vesely f170504c41 AMDGPU/R600: Serialize vector trunc stores to private AS
Add DUMMY_CHAIN SDNode to denote stores of interest

Bugzilla: https://llvm.org/bugs/show_bug.cgi?id=28915
Bugzilla: https://llvm.org/bugs/show_bug.cgi?id=30411

Differential Revision: https://reviews.llvm.org/D27964

llvm-svn: 292651
2017-01-20 21:24:26 +00:00
Matt Arsenault 3e6f9b5773 AMDGPU: Disable some fneg combines unless nsz
For -(x + y) -> (-x) + (-y), if x == -y, this would
change the result from -0.0 to 0.0. Since the fma/fmad
combine is an extension of this problem it also
applies there.

fmul should be fine, and I don't think any of the unary
operators or conversions should be a problem either.

llvm-svn: 292473
2017-01-19 06:35:27 +00:00
Matt Arsenault 45337df08f AMDGPU: Skip fneg/select combine if it can fold into other
llvm-svn: 291792
2017-01-12 18:58:15 +00:00
Matt Arsenault 31c039ef2e AMDGPU: Fold free fneg into sin
llvm-svn: 291790
2017-01-12 18:48:09 +00:00
Matt Arsenault a8c325e2f5 AMDGPU: Fold fneg into fmul_legacy
llvm-svn: 291784
2017-01-12 18:26:30 +00:00
Matt Arsenault ff7e5aadf5 AMDGPU: Fold fneg into rcp
llvm-svn: 291779
2017-01-12 17:46:35 +00:00
Matt Arsenault 4242d48c36 AMDGPU: Fold fneg into fp_round
llvm-svn: 291778
2017-01-12 17:46:33 +00:00
Matt Arsenault 98d2bf1024 AMDGPU: Fold fneg into fp_extend
llvm-svn: 291777
2017-01-12 17:46:28 +00:00
Matt Arsenault 63f953795e AMDGPU: Fold fneg into fma or fmad
Patch mostly by Fiona Glaser

llvm-svn: 291733
2017-01-12 00:32:16 +00:00
Matt Arsenault 4103a81d6d AMDGPU: Fold fneg into fmul
Patch mostly by Fiona Glaser

llvm-svn: 291732
2017-01-12 00:23:20 +00:00
Matt Arsenault 2529fba989 AMDGPU: Fold fneg into fadd
Patch mostly by Fiona Glaser

llvm-svn: 291731
2017-01-12 00:09:34 +00:00
Matt Arsenault 2a04ff97ad AMDGPU: Pull fneg/fabs out of a select
Allows better source modifier usage.

llvm-svn: 291729
2017-01-11 23:57:38 +00:00
Matt Arsenault 8871683d60 AMDGPU: Add tests for HasMultipleConditionRegisters
This was enabled without many specific tests or the comment.

llvm-svn: 291586
2017-01-10 19:08:15 +00:00
Jan Vesely 06200bd7bc AMDGPU/R600: Don't use REGISTER_{LOAD,STORE} ISD nodes
This will make transition to SCRATCH_MEMORY easier

Differential Revision: https://reviews.llvm.org/D24746

llvm-svn: 291279
2017-01-06 21:00:46 +00:00
Jan Vesely d48445d513 AMDGPU/SI: Implement sendmsghalt intrinsic
v2: expose using amdgcn prefix

Differential Revision: https://reviews.llvm.org/D23511

llvm-svn: 290977
2017-01-04 18:06:55 +00:00
Matt Arsenault 0b26e47345 AMDGPU: Invert cmp + select with constant
Canonicalize a select with a constant to the false side. This
enables more instruction shrinking opportunities since an
inline immediate can be used for the false side of v_cndmask_b32_e32.

This seems to usually be better but causes some code size regressions
in some tests.

llvm-svn: 290372
2016-12-22 21:40:08 +00:00
Matt Arsenault 4e55c1ec11 AMDGPU: Update isFPImmLegal for f16
I don't think this matters because ConstantFP is legal.

llvm-svn: 290299
2016-12-22 03:05:30 +00:00
Tom Stellard 6f9ef14b9d AMDGPU/SI: Add a MachineMemOperand when lowering llvm.amdgcn.buffer.load.*
Reviewers: arsenm, nhaehnle, mareko

Subscribers: kzhuravl, wdng, yaxunl, llvm-commits, tony-tye

Differential Revision: https://reviews.llvm.org/D27834

llvm-svn: 290184
2016-12-20 17:19:44 +00:00
Matt Arsenault 0b386360c5 AMDGPU: Fix asserting on returned tail calls
llvm-svn: 289868
2016-12-15 20:50:12 +00:00
Nirav Dave f5bf03c7ef Revert "In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled."
Reverting due to ARM MCJIT and MIPS LLD error.

This reverts commit r289659.

llvm-svn: 289667
2016-12-14 16:43:44 +00:00
Nirav Dave 8527ab0ad2 In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled.
Retrying after fixing after removing load-store factoring through
token factors in favor of improved token factor operand pruning

Simplify Consecutive Merge Store Candidate Search

Now that address aliasing is much less conservative, push through
simplified store merging search which only checks for parallel stores
through the chain subgraph. This is cleaner as the separation of
non-interfering loads/stores from the store-merging logic.

Whem merging stores, search up the chain through a single load, and
finds all possible stores by looking down from through a load and a
TokenFactor to all stores visited. This improves the quality of the
output SelectionDAG and generally the output CodeGen (with some
exceptions).

Additional Minor Changes:

   1. Finishes removing unused AliasLoad code
   2. Unifies the the chain aggregation in the merged stores across
      code paths
   3. Re-add the Store node to the worklist after calling
      SimplifyDemandedBits.
   4. Increase GatherAllAliasesMaxDepth from 6 to 18. That number is
      arbitrary, but seemed sufficient to not cause regressions in
      tests.

This finishes the change Matt Arsenault started in r246307 and
jyknight's original patch.

Many tests required some changes as memory operations are now
reorderable. Some tests relying on the order were changed to use
volatile memory operations

Noteworthy tests:

    CodeGen/AArch64/argument-blocks.ll -
      It's not entirely clear what the test_varargs_stackalign test is
      supposed to be asserting, but the new code looks right.

    CodeGen/AArch64/arm64-memset-inline.lli -
    CodeGen/AArch64/arm64-stur.ll -
    CodeGen/ARM/memset-inline.ll -

      The backend now generates *worse* code due to store merging
      succeeding, as we do do a 16-byte constant-zero store efficiently.

    CodeGen/AArch64/merge-store.ll -
      Improved, but there still seems to be an extraneous vector insert
      from an element to itself?

    CodeGen/PowerPC/ppc64-align-long-double.ll -
      Worse code emitted in this case, due to the improved store->load
      forwarding.

    CodeGen/X86/dag-merge-fast-accesses.ll -
    CodeGen/X86/MergeConsecutiveStores.ll -
    CodeGen/X86/stores-merging.ll -
    CodeGen/Mips/load-store-left-right.ll -
      Restored correct merging of non-aligned stores

    CodeGen/AMDGPU/promote-alloca-stored-pointer-value.ll -
      Improved. Correctly merges buffer_store_dword calls

    CodeGen/AMDGPU/si-triv-disjoint-mem-access.ll -
      Improved. Sidesteps loading a stored value and
      merges two stores

    CodeGen/X86/pr18023.ll -
      This test has been removed, as it was asserting incorrect
      behavior. Non-volatile stores *CAN* be moved past volatile loads,
      and now are.

    CodeGen/X86/vector-idiv.ll -
    CodeGen/X86/vector-lzcnt-128.ll -
      It's basically impossible to tell what these tests are actually
      testing. But, looks like the code got better due to the memory
      operations being recognized as non-aliasing.

    CodeGen/X86/win32-eh.ll -
      Both loads of the securitycookie are now merged.

Reviewers: arsenm, hfinkel, tstellarAMD, jyknight, nhaehnle

Subscribers: wdng, nhaehnle, nemanjai, arsenm, weimingz, niravd, RKSimon, aemerson, qcolombet, dsanders, resistor, tstellarAMD, t.p.northover, spatel

Differential Revision: https://reviews.llvm.org/D14834

llvm-svn: 289659
2016-12-14 15:44:26 +00:00
Stephan Bergmann 17c7f70362 Replace APFloatBase static fltSemantics data members with getter functions
At least the plugin used by the LibreOffice build
(<https://wiki.documentfoundation.org/Development/Clang_plugins>) indirectly
uses those members (through inline functions in LLVM/Clang include files in turn
using them), but they are not exported by utils/extract_symbols.py on Windows,
and accessing data across DLL/EXE boundaries on Windows is generally
problematic.

Differential Revision: https://reviews.llvm.org/D26671

llvm-svn: 289647
2016-12-14 11:57:17 +00:00
Matt Arsenault 38d8ed2b75 AMDGPU: Fix i128 mul
llvm-svn: 289231
2016-12-09 17:49:14 +00:00
Nirav Dave bedb5d906c Revert "In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled."
This reverts commit r289221 which appears to be triggering an assertion

llvm-svn: 289226
2016-12-09 17:18:24 +00:00
Nirav Dave fd51ff4fd8 In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled.
Retrying after fixing overly aggressive load-store forwarding optimization.

Simplify Consecutive Merge Store Candidate Search

Now that address aliasing is much less conservative, push through
simplified store merging search which only checks for parallel stores
through the chain subgraph. This is cleaner as the separation of
non-interfering loads/stores from the store-merging logic.

Whem merging stores, search up the chain through a single load, and
finds all possible stores by looking down from through a load and a
TokenFactor to all stores visited. This improves the quality of the
output SelectionDAG and generally the output CodeGen (with some
exceptions).

Additional Minor Changes:

   1. Finishes removing unused AliasLoad code
   2. Unifies the the chain aggregation in the merged stores across
      code paths
   3. Re-add the Store node to the worklist after calling
      SimplifyDemandedBits.
   4. Increase GatherAllAliasesMaxDepth from 6 to 18. That number is
      arbitrary, but seemed sufficient to not cause regressions in
      tests.

This finishes the change Matt Arsenault started in r246307 and
jyknight's original patch.

Many tests required some changes as memory operations are now
reorderable. Some tests relying on the order were changed to use
volatile memory operations

Noteworthy tests:

    CodeGen/AArch64/argument-blocks.ll -
      It's not entirely clear what the test_varargs_stackalign test is
      supposed to be asserting, but the new code looks right.

    CodeGen/AArch64/arm64-memset-inline.lli -
    CodeGen/AArch64/arm64-stur.ll -
    CodeGen/ARM/memset-inline.ll -

      The backend now generates *worse* code due to store merging
      succeeding, as we do do a 16-byte constant-zero store efficiently.

    CodeGen/AArch64/merge-store.ll -
      Improved, but there still seems to be an extraneous vector insert
      from an element to itself?

    CodeGen/PowerPC/ppc64-align-long-double.ll -
      Worse code emitted in this case, due to the improved store->load
      forwarding.

    CodeGen/X86/dag-merge-fast-accesses.ll -
    CodeGen/X86/MergeConsecutiveStores.ll -
    CodeGen/X86/stores-merging.ll -
    CodeGen/Mips/load-store-left-right.ll -
      Restored correct merging of non-aligned stores

    CodeGen/AMDGPU/promote-alloca-stored-pointer-value.ll -
      Improved. Correctly merges buffer_store_dword calls

    CodeGen/AMDGPU/si-triv-disjoint-mem-access.ll -
      Improved. Sidesteps loading a stored value and
      merges two stores

    CodeGen/X86/pr18023.ll -
      This test has been removed, as it was asserting incorrect
      behavior. Non-volatile stores *CAN* be moved past volatile loads,
      and now are.

    CodeGen/X86/vector-idiv.ll -
    CodeGen/X86/vector-lzcnt-128.ll -
      It's basically impossible to tell what these tests are actually
      testing. But, looks like the code got better due to the memory
      operations being recognized as non-aliasing.

    CodeGen/X86/win32-eh.ll -
      Both loads of the securitycookie are now merged.

Reviewers: arsenm, hfinkel, tstellarAMD, jyknight, nhaehnle

Subscribers: wdng, nhaehnle, nemanjai, arsenm, weimingz, niravd, RKSimon, aemerson, qcolombet, dsanders, resistor, tstellarAMD, t.p.northover, spatel

Differential Revision: https://reviews.llvm.org/D14834

llvm-svn: 289221
2016-12-09 16:15:12 +00:00
Tom Stellard 8485fa096e AMDGPU : Add S_SETREG instructions to fix fdiv precision issues.
Patch By: Wei Ding

Summary: This patch fixes the fdiv precision issues.

Reviewers: b-sumner, cfang, wdng, arsenm

Subscribers: kzhuravl, nhaehnle, yaxunl, tony-tye

Differential Revision: https://reviews.llvm.org/D26424

llvm-svn: 288879
2016-12-07 02:42:15 +00:00
Matt Arsenault 7bee6ac798 AMDGPU: Refactor exp instructions
Structure the definitions a bit more like the other classes.

The main change here is to split EXP with the done bit set
to a separate opcode, so we can set mayLoad = 1 so that it won't
be reordered before the other exp stores, since this has the special
constraint that if the done bit is set then this should be the last
exp in she shader.

Previously all exp instructions were inferred to have unmodeled
side effects.

llvm-svn: 288695
2016-12-05 20:23:10 +00:00
Stanislav Mekhanoshin 0ee250eee8 [AMDGPU] Allow hoisting of comparisons out of a loop and eliminate condition copies
Codegen prepare sinks comparisons close to a user is we have only one register
for conditions. For AMDGPU we have many SGPRs capable to hold vector conditions.
Changed BE to report we have many condition registers. That way IR LICM pass
would hoist an invariant comparison out of a loop and codegen prepare will not
sink it.

With that done a condition is calculated in one block and used in another.
Current behavior is to store workitem's condition in a VGPR using v_cndmask_b32
and then restore it with yet another v_cmp instruction from that v_cndmask's
result. To mitigate the issue a propagation of source SGPR pair in place of v_cmp
is implemented. Additional side effect of this is that we may consume less VGPRs
at a cost of more SGPRs in case if holding of multiple conditions is needed, and
that is a clear win in most cases.

Differential Revision: https://reviews.llvm.org/D26114

llvm-svn: 288053
2016-11-28 18:58:49 +00:00