Commit Graph

320 Commits

Author SHA1 Message Date
Ryan Taylor 29257eb76c [AMDGPU] Increases available SGPR for Calling Convention
Summary:
SGPR in CC can be either hw initialized or set by other chained shaders
and so this increases the SGPR count availalbe to CC to 105.

Change-Id: I3dfadc750fe4a3e2bd07117a2899fd13f3e2fef3

Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61261

llvm-svn: 360778
2019-05-15 14:43:55 +00:00
Simon Pilgrim e3eec06dde [AMDGPU] Reapplied BFE canonicalization from D60462
This was committed in rL358887 but reverted in rL360066 due to a x86 regression, really it should be have been pre-committed instead of being part of the SimplifyDemandedBits bitcast patch.

llvm-svn: 360263
2019-05-08 15:49:10 +00:00
Craig Topper 55a71b575c Revert r359392 and r358887
Reverts "[X86] Remove (V)MOV64toSDrr/m and (V)MOVDI2SSrr/m. Use 128-bit result MOVD/MOVQ and COPY_TO_REGCLASS instead"
Reverts "[TargetLowering][AMDGPU][X86] Improve SimplifyDemandedBits bitcast handling"

Eric Christopher and Jorge Gorbe Moya reported some issues with these patches to me off list.

Removing the CodeGenOnly instructions has changed how fneg is handled during fast-isel with sse/sse2. We're now emitting fsub -0.0, x instead
moving to the integer domain(in a GPR), xoring the sign bit, and then moving back to xmm. This is because the fast isel table no longer
contains an entry for (f32/f64 bitcast (i32/i64)) so the target independent fneg code fails. The use of fsub changes the behavior of nan with
respect to -O2 codegen which will always use a pxor. NOTE: We still have a difference with double with -m32 since the move to GPR doesn't work
there. I'll file a separate PR for that and add test cases.

Since removing the CodeGenOnly instructions was fixing PR41619, I'm reverting r358887 which exposed that PR. Though I wouldn't be surprised
if that bug can still be hit independent of that.

This should hopefully get Google back to green. I'll work with Simon and other X86 folks to figure out how to move forward again.

llvm-svn: 360066
2019-05-06 19:29:24 +00:00
Stanislav Mekhanoshin a6322941ff [AMDGPU] gfx1010 VMEM and SMEM implementation
Differential Revision: https://reviews.llvm.org/D61330

llvm-svn: 359621
2019-04-30 22:08:23 +00:00
Simon Pilgrim 6276ce0142 [TargetLowering][AMDGPU][X86] Improve SimplifyDemandedBits bitcast handling
This patch adds support for BigBitWidth -> SmallBitWidth bitcasts, splitting the DemandedBits/Elts accordingly.

The AMDGPU backend needed an extra  (srl (and x, c1 << c2), c2) -> (and (srl(x, c2), c1) combine to encourage BFE creation, I investigated putting this in DAGCombine but it caused a lot of noise on other targets - some improvements, some regressions.

The X86 changes are all definite wins.

Differential Revision: https://reviews.llvm.org/D60462

llvm-svn: 358887
2019-04-22 14:04:35 +00:00
Tim Renouf 7c55c8d8c3 [AMDGPU] Avoid DAG combining assert with fneg(fadd(A,0))
fneg combining attempts to turn it into fadd(fneg(A), fneg(0)), but
creating the new fadd folds to just fneg(A). When A has multiple uses,
this confuses it and you get an assert. Fixed.

Differential Revision: https://reviews.llvm.org/D60633

Change-Id: I0ddc9b7286abe78edc0cd8d734fdeb05ff09821c
llvm-svn: 358640
2019-04-18 05:27:01 +00:00
Tim Renouf 677387d8dc [AMDGPU] Implemented dwordx3 variants of buffer/tbuffer load/store intrinsics
Now we have vec3 MVTs, this commit implements dwordx3 variants of the
buffer intrinsics.

On gfx6, a dwordx3 buffer load intrinsic is implemented as a dwordx4
instruction, and a dwordx3 buffer store intrinsic is not supported.
We need to support the dwordx3 load intrinsic because it is generated by
subtarget-unaware code in InstCombine.

Differential Revision: https://reviews.llvm.org/D58904

Change-Id: I016729d8557b98a52f529638ae97c340a5922a4e
llvm-svn: 356755
2019-03-22 14:58:02 +00:00
Tim Renouf 033f99a2e5 [AMDGPU] Added v5i32 and v5f32 register classes
They are not used by anything yet, but a subsequent commit will start
using them for image ops that return 5 dwords.

Differential Revision: https://reviews.llvm.org/D58903

Change-Id: I63e1904081e39a6d66e4eb96d51df25ad399d271
llvm-svn: 356735
2019-03-22 10:11:21 +00:00
Tim Renouf 361b5b2193 [AMDGPU] Support for v3i32/v3f32
Added support for dwordx3 for most load/store types, but not DS, and not
intrinsics yet.

SI (gfx6) does not have dwordx3 instructions, so they are not enabled
there.

Some of this patch is from Matt Arsenault, also of AMD.

Differential Revision: https://reviews.llvm.org/D58902

Change-Id: I913ef54f1433a7149da8d72f4af54dbb13436bd9
llvm-svn: 356659
2019-03-21 12:01:21 +00:00
Ryan Taylor 00e063ab92 [AMDGPU] Add buffer/load 8/16 bit overloaded intrinsics
Summary:
Add buffer store/load 8/16 overloaded intrinsics for buffer, raw_buffer and struct_buffer

Change-Id: I166a29f071b2ff4e4683fb0392564b1f223ac61d

Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59265

llvm-svn: 356465
2019-03-19 16:07:00 +00:00
Adhemerval Zanella 664c1ef528 [TargetLowering] Add code size information on isFPImmLegal. NFC
This allows better code size for aarch64 floating point materialization
in a future patch.

Reviewers: evandro

Differential Revision: https://reviews.llvm.org/D58690

llvm-svn: 356389
2019-03-18 18:40:07 +00:00
Tim Renouf e30aa6a136 [AMDGPU] Prepare for introduction of v3 and v5 MVTs
AMDGPU would like to have MVTs for v3i32, v3f32, v5i32, v5f32. This
commit does not add them, but makes preparatory changes:

* Fixed assumptions of power-of-2 vector type in kernel arg handling,
  and added v5 kernel arg tests and v3/v5 shader arg tests.

* Added v5 tests for cost analysis.

* Added vec3/vec5 arg test cases.

Some of this patch is from Matt Arsenault, also of AMD.

Differential Revision: https://reviews.llvm.org/D58928

Change-Id: I7279d6b4841464d2080eb255ef3c589e268eabcd
llvm-svn: 356342
2019-03-17 21:04:16 +00:00
Matt Arsenault e8c03a2511 AMDGPU: Move d16 load matching to preprocess step
When matching half of the build_vector to a load, there could still be
a hidden dependency on the other half of the build_vector the pattern
wouldn't detect. If there was an additional chain dependency on the
other value, a cycle could be introduced.

I don't think a tablegen pattern is capable of matching the necessary
conditions, so move this into PreprocessISelDAG. Check isPredecessorOf
for the other value to avoid a cycle. This has a warning that it's
expensive, so this should probably be moved into an MI pass eventually
that will have more freedom to reorder instructions to help match
this. That is currently complicated by the lack of a computeKnownBits
type mechanism for the selected function.

llvm-svn: 355731
2019-03-08 20:58:11 +00:00
Matt Arsenault aa03bcd23c AMDGPU: Fix crashes in invalid call cases
We have to at least tolerate calls to kernels, possibly with a
mismatched calling convention on the callsite.

llvm-svn: 355049
2019-02-28 00:28:44 +00:00
Craig Topper 784929d045 Implementation of asm-goto support in LLVM
This patch accompanies the RFC posted here:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/127239.html

This patch adds a new CallBr IR instruction to support asm-goto
inline assembly like gcc as used by the linux kernel. This
instruction is both a call instruction and a terminator
instruction with multiple successors. Only inline assembly
usage is supported today.

This also adds a new INLINEASM_BR opcode to SelectionDAG and
MachineIR to represent an INLINEASM block that is also
considered a terminator instruction.

There will likely be more bug fixes and optimizations to follow
this, but we felt it had reached a point where we would like to
switch to an incremental development model.

Patch by Craig Topper, Alexander Ivchenko, Mikhail Dvoretckii

Differential Revision: https://reviews.llvm.org/D53765

llvm-svn: 353563
2019-02-08 20:48:56 +00:00
Matt Arsenault a3f9b71c09 AMDGPU: Fix assert on trunc from bitcast of build_vector
The v2i64 argument is lowered to a bitcast of v4i32 build_vector.
This would then attempt to use the i32-element as the source of the
vector truncate. This really would need to collect 2 elements from the
build_vector to produce the intended truncate.

llvm-svn: 353202
2019-02-05 19:23:57 +00:00
Tim Corringham 824ca3f3dd [AMDGPU] Add intrinsics for 16 bit interpolation
Summary:
Added the intrinsics llvm.amdgcn.interp.p1.f16() and
llvm.amdgcn.interp.p2.f16() and related LIT test.

The p1 intrinsic generates code appropriate for both 16 and 32
bank LDS.

Reviewers: #amdgpu, dstuttard, arsenm, tpr

Reviewed By: #amdgpu, arsenm

Subscribers: jvesely, mgorny, arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D46754

llvm-svn: 352357
2019-01-28 13:48:59 +00:00
Matt Arsenault a5840c3c39 Codegen support for atomicrmw fadd/fsub
llvm-svn: 351851
2019-01-22 18:36:06 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
Matt Arsenault 85af701e85 AMDGPU: Remove llvm.SI.load.const
It's taken 3 years, but now all of the old AMDGPU and SI intrinsics
are finally gone

llvm-svn: 351586
2019-01-18 20:27:02 +00:00
Marek Olsak c5cec5e1fa AMDGPU: Add llvm.amdgcn.ds.ordered.add & swap
Reviewers: arsenm, nhaehnle

Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D52944

llvm-svn: 351351
2019-01-16 15:43:53 +00:00
Craig Topper 826f44b550 [TargetLowering][AMDGPU] Remove the SimplifyDemandedBits function that takes a User and OpIdx. Stop using it in AMDGPU target for simplifyI24.
As we saw in D56057 when we tried to use this function on X86, it's unsafe. It allows the operand node to have multiple users, but doesn't prevent recursing past the first node when it does have multiple users. This can cause other simplifications earlier in the graph without regard to what bits are needed by the other users of the first node. Ideally all we should do to the first node if it has multiple uses is bypass it when its not needed by the user we started from. Doing any other transformation that SimplifyDemandedBits can do like turning ZEXT/SEXT into AEXT would result in an increase in instructions.

Fortunately, we already have a function that can do just that, GetDemandedBits. It will only make transformations that involve bypassing a node.

This patch changes AMDGPU's simplifyI24, to use a combination of GetDemandedBits to handle the multiple use simplifications. And then uses the regular SimplifyDemandedBits on each operand to handle simplifications allowed when the operand only has a single use. Unfortunately, GetDemandedBits simplifies constants more aggressively than SimplifyDemandedBits. This caused the -7 constant in the changed test to be simplified to remove the upper bits. I had to modify computeKnownBits to account for this by ignoring the upper 8 bits of the input.

Differential Revision: https://reviews.llvm.org/D56087

llvm-svn: 350560
2019-01-07 19:30:43 +00:00
Simon Pilgrim 3c157d3fa3 [AMDGPU] Always use the version of computeKnownBits that returns a value. NFCI.
Continues the work started by @bogner in rL340594 to remove uses of the KnownBits output paramater version.

llvm-svn: 349912
2018-12-21 15:29:47 +00:00
Sanjay Patel 0a515595a7 [x86] allow vector load narrowing with multi-use values
This is a long-awaited follow-up suggested in D33578. Since then, we've picked up even more
opportunities for vector narrowing from changes like D53784, so there are a lot of test diffs.
Apart from 2-3 strange cases, these are all wins.

I've structured this to be no-functional-change-intended for any target except for x86
because I couldn't tell if AArch64, ARM, and AMDGPU would improve or not. All of those
targets have existing regression tests (4, 4, 10 files respectively) that would be
affected. Also, Hexagon overrides the shouldReduceLoadWidth() hook, but doesn't show
any regression test diffs. The trade-off is deciding if an extra vector load is better
than a single wide load + extract_subvector.

For x86, this is almost always better (on paper at least) because we often can fold
loads into subsequent ops and not increase the official instruction count. There's also
some unknown -- but potentially large -- benefit from using narrower vector ops if wide
ops are implemented with multiple uops and/or frequency throttling is avoided.

Differential Revision: https://reviews.llvm.org/D54073

llvm-svn: 346595
2018-11-10 20:05:31 +00:00
Matt Arsenault 8e0269ba0b AMDGPU: Fix assertion with bitcast from i64 constant to v4i16
llvm-svn: 345922
2018-11-02 02:43:55 +00:00
Stanislav Mekhanoshin 222e9c11f7 Check shouldReduceLoadWidth from SimplifySetCC
SimplifySetCC could shrink a load without checking for
profitability or legality of such shink with a target.

Added checks to prevent shrinking of aligned scalar loads
in AMDGPU below dword as scalar engine does not support it.

Differential Revision: https://reviews.llvm.org/D53846

llvm-svn: 345778
2018-10-31 21:24:30 +00:00
Matt Arsenault 687ec75d10 DAG: Change behavior of fminnum/fmaxnum nodes
Introduce new versions that follow the IEEE semantics
to help with legalization that may need quieted inputs.

There are some regressions from inserting unnecessary
canonicalizes when these are matched from fast math
fcmp + select which should be fixed in a future commit.

llvm-svn: 344914
2018-10-22 16:27:27 +00:00
Matt Arsenault ab41193312 AMDGPU: Expand atomicrmw nand in IR
llvm-svn: 343559
2018-10-02 03:50:56 +00:00
Matt Arsenault 9d49c449ec AMDGPU: Expand vector canonicalizes
llvm-svn: 342439
2018-09-18 01:51:33 +00:00
Matt Arsenault 0da6350dc8 AMDGPU: Remove remnants of old address space mapping
llvm-svn: 341165
2018-08-31 05:49:54 +00:00
Tim Renouf 904343f879 [AMDGPU] Add support for multi-dword s.buffer.load intrinsic
Summary:
Patch by Marek Olsak and David Stuttard, both of AMD.

This adds a new amdgcn intrinsic supporting s.buffer.load, in particular
multiple dword variants. These are convenient to use from some front-end
implementations.

Also modified the existing llvm.SI.load.const intrinsic to common up the
underlying implementation.

This modification also requires that we can lower to non-uniform loads correctly
by splitting larger dword variants into sizes supported by the non-uniform
versions of the load.

V2: Addressed minor review comments.
V3: i1 glc is now i32 cachepolicy for consistency with buffer and
    tbuffer intrinsics, plus fixed formatting issue.
V4: Added glc test.

Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D51098

Change-Id: I83a6e00681158bb243591a94a51c7baa445f169b
llvm-svn: 340684
2018-08-25 14:53:17 +00:00
Matt Arsenault bb8e64e7f5 AMDGPU: Fix not respecting byval alignment in call frame setup
This was hackily adding in the 4-bytes reserved for the callee's
emergency stack slot. Treat it like a normal stack allocation
so we get the correct alignment padding behavior. This fixes
an inconsistency between the caller and callee.

llvm-svn: 340396
2018-08-22 11:09:45 +00:00
Matt Arsenault 7121bed210 AMDGPU: Custom lower fexp
This will allow the library to just use __builtin_expf directly
without expanding this itself. Note f64 still won't work because
there is no exp instruction for it.

llvm-svn: 339902
2018-08-16 17:07:52 +00:00
Matt Arsenault f533e6b0ed AMDGPU: Fold fneg into fmed3
llvm-svn: 339821
2018-08-15 21:46:27 +00:00
Matt Arsenault 6c7ba82900 AMDGPU: Address todo for handling 1/(2 pi)
llvm-svn: 339814
2018-08-15 21:03:55 +00:00
Matt Arsenault 940e6075e4 AMDGPU: More canonicalized operations
llvm-svn: 339464
2018-08-10 19:20:17 +00:00
Matt Arsenault 08f3fe4fae AMDGPU: cvt_pk_rtz_f16 canonicalizes
llvm-svn: 339078
2018-08-06 23:01:31 +00:00
Matt Arsenault d49ab0b214 AMDGPU: Treat more custom operations as canonicalizing
Everything should quiet, and I think everything should
flush.

I assume the min3/med3/max3 follow the same rules
as regular min/max for flushing, which should at
least be conservatively correct.

There are still more operations that need to
be handled.

llvm-svn: 339065
2018-08-06 21:58:11 +00:00
Matt Arsenault c3dc8e65e2 DAG: Enhance isKnownNeverNaN
Add a parameter for testing specifically for
sNaNs - at least one instruction pattern on AMDGPU
needs to check specifically for this.

Also handle more cases, and add a target hook
for custom nodes, similar to the hooks for known
bits.

llvm-svn: 338910
2018-08-03 18:27:52 +00:00
Matt Arsenault f3c9a34def AMDGPU: Make fneg combine handle fcanonicalize
llvm-svn: 338243
2018-07-30 12:16:47 +00:00
Matt Arsenault 81920b0a25 DAG: Add calling convention argument to calling convention funcs
This seems like a pretty glaring omission, and AMDGPU
wants to treat kernels differently from other calling
conventions.

llvm-svn: 338194
2018-07-28 13:25:19 +00:00
Matt Arsenault 72b0e38b26 AMDGPU: Stop trying to extend arguments for clover
This was trying to replace i8/i16 arguments with i32, which
was broken and no longer necessary.

llvm-svn: 338193
2018-07-28 12:34:25 +00:00
Matt Arsenault 4bec7d4261 Reapply "AMDGPU: Fix handling of alignment padding in DAG argument lowering"
Reverts r337079 with fix for msan error.

llvm-svn: 337535
2018-07-20 09:05:08 +00:00
Farhana Aleen c370d7b33d [AMDGPU] [AMDGPU] Support a fdot2 pattern.
Summary: Optimize fma((float)S0.x, (float)S1.x fma((float)S0.y, (float)S1.y, z))
                   -> fdot2((v2f16)S0, (v2f16)S1, (float)z)

Author: FarhanaAleen

Reviewed By: rampitec, b-sumner

Subscribers: AMDGPU

Differential Revision: https://reviews.llvm.org/D49146

llvm-svn: 337198
2018-07-16 18:19:59 +00:00
Evgeniy Stepanov 1971ba097d Revert "AMDGPU: Fix handling of alignment padding in DAG argument lowering"
This reverts commit r337021.

WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x1415cd65 in void write_signed<long>(llvm::raw_ostream&, long, unsigned long, llvm::IntegerStyle) /code/llvm-project/llvm/lib/Support/NativeFormatting.cpp:95:7
    #1 0x1415c900 in llvm::write_integer(llvm::raw_ostream&, long, unsigned long, llvm::IntegerStyle) /code/llvm-project/llvm/lib/Support/NativeFormatting.cpp:121:3
    #2 0x1472357f in llvm::raw_ostream::operator<<(long) /code/llvm-project/llvm/lib/Support/raw_ostream.cpp:117:3
    #3 0x13bb9d4 in llvm::raw_ostream::operator<<(int) /code/llvm-project/llvm/include/llvm/Support/raw_ostream.h:210:18
    #4 0x3c2bc18 in void printField<unsigned int, &(amd_kernel_code_s::amd_kernel_code_version_major)>(llvm::StringRef, amd_kernel_code_s const&, llvm::raw_ostream&) /code/llvm-project/llvm/lib/Target/AMDGPU/Utils/AMDKernelCodeTUtils.cpp:78:23
    #5 0x3c250ba in llvm::printAmdKernelCodeField(amd_kernel_code_s const&, int, llvm::raw_ostream&) /code/llvm-project/llvm/lib/Target/AMDGPU/Utils/AMDKernelCodeTUtils.cpp:104:5
    #6 0x3c27ca3 in llvm::dumpAmdKernelCode(amd_kernel_code_s const*, llvm::raw_ostream&, char const*) /code/llvm-project/llvm/lib/Target/AMDGPU/Utils/AMDKernelCodeTUtils.cpp:113:5
    #7 0x3a46e6c in llvm::AMDGPUTargetAsmStreamer::EmitAMDKernelCodeT(amd_kernel_code_s const&) /code/llvm-project/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUTargetStreamer.cpp:161:3
    #8 0xd371e4 in llvm::AMDGPUAsmPrinter::EmitFunctionBodyStart() /code/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp:204:26

[...]

Uninitialized value was created by an allocation of 'KernelCode' in the stack frame of function '_ZN4llvm16AMDGPUAsmPrinter21EmitFunctionBodyStartEv'
    #0 0xd36650 in llvm::AMDGPUAsmPrinter::EmitFunctionBodyStart() /code/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp:192

llvm-svn: 337079
2018-07-14 01:20:53 +00:00
Matt Arsenault de95077780 AMDGPU: Fix handling of alignment padding in DAG argument lowering
This was completely broken if there was ever a struct argument, as
this information is thrown away during the argument analysis.

The offsets as passed in to LowerFormalArguments are not useful,
as they partially depend on the legalized result register type,
and they don't consider the alignment in the first place.

Ignore the Ins array, and instead figure out from the raw IR type
what we need to do. This seems to fix the padding computation
if the DAG lowering is forced (and stops breaking arguments
following padded arguments if the arguments were only partially
lowered in the IR)

llvm-svn: 337021
2018-07-13 16:40:25 +00:00
Matt Arsenault 4dca0a9904 AMDGPU: Fix assert in truncate combine with vectors
The piece above probably has the same problem, but I need
to try to come up with a test for it.

llvm-svn: 336935
2018-07-12 19:40:16 +00:00
Tom Stellard 5bfbae5cb1 AMDGPU: Refactor Subtarget classes
Summary:
This is a follow-up to r335942.
- Merge SISubtarget into AMDGPUSubtarget and rename to GCNSubtarget
- Rename AMDGPUCommonSubtarget to AMDGPUSubtarget
- Merge R600Subtarget::Generation and GCNSubtarget::Generation into
  AMDGPUSubtarget::Generation.

Reviewers: arsenm, jvesely

Subscribers: kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D49037

llvm-svn: 336851
2018-07-11 20:59:01 +00:00
Tom Stellard ec4feae1b6 AMDGPU: Fix UBSan error caused by r335942
Summary: Fixes PR38071.

Reviewers: arsenm, dstenb

Reviewed By: arsenm

Subscribers: kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D48979

llvm-svn: 336448
2018-07-06 17:16:17 +00:00
Matt Arsenault 29f303799b AMDGPU/GlobalISel: Implement custom kernel arg lowering
Avoid using allocateKernArg / AssignFn. We do not want any
of the type splitting properties of normal calling convention
lowering.

For now at least this exists alongside the IR argument lowering
pass. This is necessary to handle struct padding correctly while
some arguments are still skipped by the IR argument lowering
pass.

llvm-svn: 336373
2018-07-05 17:01:20 +00:00