[mlir] Add padding to 1-D Vector in CRunnerUtils.h

[nicolasvasilache]

Summary

This revision adds padding for 1-D Vector in the common case of x86
execution with a stadard data layout. This supports properly interfacing
codegen with arrays of e.g. vector<9xf32>.

Such vectors are already assumed padded to the next power of 2 by LLVM
codegen with the default x86 data layout:

define void @test_vector_add_1d_2_3(<3 x float>* nocapture readnone %0,
<3 x float>* nocapture readonly %1, i64 %2, i64 %3, i64 %4, <3 x float>*
nocapture readnone %5, <3 x float>* nocapture readonly %6, i64 %7, i64
%8, i64 %9, <3 x float>* nocapture readnone %10, <3 x float>* nocapture
%11, i64 %12, i64 %13, i64 %14) local_unnamed_addr {
  %16 = getelementptr <3 x float>, <3 x float>* %6, i64 1
  %17 = load <3 x float>, <3 x float>* %16, align 16
  %18 = getelementptr <3 x float>, <3 x float>* %1, i64 1
  %19 = load <3 x float>, <3 x float>* %18, align 16
  %20 = fadd <3 x float> %17, %19
  %21 = getelementptr <3 x float>, <3 x float>* %11, i64 1

The pointer addressing a vector<3xf32> is assumed aligned @16.
Similarly, the pointer addressing a vector<65xf32> is assumed aligned
@512.

This revision allows using objects such as vector<3xf32> properly with
the standard x86 data layout used in the JitRunner. Integration testing
is done out of tree, at the moment such testing fails without this
change.

[nicolasvasilache]

Update assertions.

[nicolasvasilache]

Format.

[stella.stamenova]

I'm seeing an error on Windows with this:

##[error]mlir\include\mlir\ExecutionEngine\CRunnerUtils.h(93,0): Error C2672: 'detail::nextPowerOf2': no matching overloaded function found
   378>E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(93): error C2672: 'detail::nextPowerOf2': no matching overloaded function found [E:\agent\_work\4\b\tools\mlir\test\mlir-cpu-runner\cblas.vcxproj]
         E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(94): note: see reference to class template instantiation 'detail::Vector1D<T,Dim,false>' being compiled
##[error]mlir\include\mlir\ExecutionEngine\CRunnerUtils.h(93,0): Error C2975: 'N': invalid template argument for 'detail::nextPowerOf2', expected compile-time constant expression
   378>E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(93): error C2975: 'N': invalid template argument for 'detail::nextPowerOf2', expected compile-time constant expression [E:\agent\_work\4\b\tools\mlir\test\mlir-cpu-runner\cblas.vcxproj]
         E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(58): note: see declaration of 'N'
##[error]mlir\include\mlir\ExecutionEngine\CRunnerUtils.h(113,0): Error C2672: 'detail::isPowerOf2': no matching overloaded function found
   378>E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(113): error C2672: 'detail::isPowerOf2': no matching overloaded function found [E:\agent\_work\4\b\tools\mlir\test\mlir-cpu-runner\cblas.vcxproj]
         E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(113): note: see reference to class template instantiation 'Vector<T,Dim,>' being compiled
##[error]mlir\include\mlir\ExecutionEngine\CRunnerUtils.h(113,0): Error C2975: 'N': invalid template argument for 'detail::isPowerOf2', expected compile-time constant expression
   378>E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(113): error C2975: 'N': invalid template argument for 'detail::isPowerOf2', expected compile-time constant expression [E:\agent\_work\4\b\tools\mlir\test\mlir-cpu-runner\cblas.vcxproj]
         E:\agent\_work\4\s\mlir\include\mlir/ExecutionEngine/CRunnerUtils.h(43): note: see declaration of 'N'

[nicolasvasilache]

@stella.stamenova this seems related: https://developercommunityapi.westus.cloudapp.azure.com/content/problem/110435/not-compile-time-constant-expression.html
This is marked as "fixed in: visual studio 2019 version 16.2"

[stella.stamenova]

In D75459#1903822, @nicolasvasilache wrote:

@stella.stamenova this seems related: https://developercommunityapi.westus.cloudapp.azure.com/content/problem/110435/not-compile-time-constant-expression.html
This is marked as "fixed in: visual studio 2019 version 16.2"

We are still using VS 2017 because of the bug in some versions of VS 2019 that hits LLVM (https://developercommunity.visualstudio.com/content/problem/845933/miscompile-boolean-condition-deduced-to-be-always.html).

[nicolasvasilache]

@stella.stamenova this seems a bit tricky to fix at a distance for me, can you propose a patch that would selectively disable what your particular version of MSVC does not support for now with a TODO once it can be reactivated?

[flaub]

mlir/include/mlir/ExecutionEngine/CRunnerUtils.h

42

We should be able to replace this chunk with:

constexpr bool isPowerOf2(int N) { return (!(N & (N - 1))); }

constexpr unsigned nextPowerOf2(int N) {
  if (N < 1)
    return 1;
  return isPowerOf2(N) ? N : 2 * nextPowerOf2((N + 1) / 2);
}

This should work on C++11 and also works with MSVC.

[flaub]

mlir/include/mlir/ExecutionEngine/CRunnerUtils.h

85

With the above change, this can be:

char padding[detail::nextPowerOf2(sizeof(T[Dim])) - sizeof(T[Dim])];

Which I think is both easier to read and works on MSVC. We should probably try to use constexpr functions over template specialization now that we can use C++11.

[flaub]

See https://reviews.llvm.org/D75584 for a potential fix.

[nicolasvasilache]

thanks much @flaub !