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Commit Graph

184 Commits

Author SHA1 Message Date
Matt Arsenault
7b541d6cfd 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
8df97c1243 AMDGPU: Support v2i16/v2f16 packed operations
llvm-svn: 296396
2017-02-27 22:15:25 +00:00
Wei Ding
eeeaa7242c 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
d2e2dba6a0 AMDGPU: Add cvt.pkrtz intrinsic
Convert llvm.SI.packf16 test uses

llvm-svn: 295797
2017-02-22 00:27:34 +00:00
Matt Arsenault
65d8dccee7 AMDGPU: Remove llvm.AMDGPU.clamp intrinsic
llvm-svn: 295789
2017-02-21 23:46:04 +00:00
Matt Arsenault
73b8eb1cc6 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
478a09d3d1 AMDGPU: Add pass to expand memcpy/memmove/memset
llvm-svn: 294635
2017-02-09 22:00:42 +00:00
Matt Arsenault
b1837f2207 AMDGPU: Fold fneg into fmin/fmax_legacy
llvm-svn: 293972
2017-02-03 00:51:50 +00:00
Matt Arsenault
a7a8104cc4 AMDGPU: Fold fneg into fminnum/fmaxnum
llvm-svn: 293968
2017-02-03 00:23:15 +00:00
Matt Arsenault
fb406eaa7d 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
63300d8c5e 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
d4909b474b 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
93d42a5136 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
97f77d5d8b 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
f2ec17e0e6 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
d839aa304c 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
ca8f087f31 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
5809e12d46 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
2a565d7a4e 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
c7f26fe4ae 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
a3987fa2ed AMDGPU: Fold fneg into round instructions
llvm-svn: 293127
2017-01-26 01:25:36 +00:00
Matt Arsenault
dd08415714 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
dc9e7b7339 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
ff7ad6a7f3 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
e493fa036b AMDGPU: Skip fneg/select combine if it can fold into other
llvm-svn: 291792
2017-01-12 18:58:15 +00:00
Matt Arsenault
9901525f48 AMDGPU: Fold free fneg into sin
llvm-svn: 291790
2017-01-12 18:48:09 +00:00
Matt Arsenault
c660bfe147 AMDGPU: Fold fneg into fmul_legacy
llvm-svn: 291784
2017-01-12 18:26:30 +00:00
Matt Arsenault
29ff5d7995 AMDGPU: Fold fneg into rcp
llvm-svn: 291779
2017-01-12 17:46:35 +00:00
Matt Arsenault
a1e740ea09 AMDGPU: Fold fneg into fp_round
llvm-svn: 291778
2017-01-12 17:46:33 +00:00
Matt Arsenault
e4f0519d94 AMDGPU: Fold fneg into fp_extend
llvm-svn: 291777
2017-01-12 17:46:28 +00:00
Matt Arsenault
595d567731 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
9b4e6e8e41 AMDGPU: Fold fneg into fmul
Patch mostly by Fiona Glaser

llvm-svn: 291732
2017-01-12 00:23:20 +00:00
Matt Arsenault
e25ed6e79f AMDGPU: Fold fneg into fadd
Patch mostly by Fiona Glaser

llvm-svn: 291731
2017-01-12 00:09:34 +00:00
Matt Arsenault
36b1afa3ef 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
9cbcb1f0dc 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
523782f6c1 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
25eec05837 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
1edd642a1d 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
5979870866 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
2c0dd4ec69 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
feb1ec1fb2 AMDGPU: Fix asserting on returned tail calls
llvm-svn: 289868
2016-12-15 20:50:12 +00:00
Nirav Dave
9fd3ae9cf9 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
afe2eccae3 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
aba15d97df 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
eb15d80d21 AMDGPU: Fix i128 mul
llvm-svn: 289231
2016-12-09 17:49:14 +00:00
Nirav Dave
0b475dec77 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
075ae0197d 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
42afa7429f 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
fdf7e5830b 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
92eac85076 [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