[NVPTX] Integrate ptxas to LIT tests

ptxas is a proprietary compiler from Nvidia that can compile PTX to
machine code (SASS). It has a lot of diagnostics to catch errors
in PTX, which can be used to

[NVPTX] Integrate ptxas to LIT tests

ptxas is a proprietary compiler from Nvidia that can compile PTX to
machine code (SASS). It has a lot of diagnostics to catch errors
in PTX, which can be used to verify PTX output from llc.

Set -DPXTAS_EXECUTABLE=/path/to/ptxas CMake option to enable it.
If this option is not set, then ptxas is substituted to true which
effectively disables all ptxas RUN lines.

LLVM_PTXAS_EXECUTABLE environment variable takes precedence over
the CMake option, and allows to override ptxas executable that is used for LIT
without complete re-configuration.

Differential Revision: https://reviews.llvm.org/D121727

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[NVPTX] Use opaque pointers in param space vectorization tests

Opaque pointers are enabled by default since D123300, so test IR should be
regenerated correspondingly.

Differential Revision: https:/

[NVPTX] Use opaque pointers in param space vectorization tests

Opaque pointers are enabled by default since D123300, so test IR should be
regenerated correspondingly.

Differential Revision: https://reviews.llvm.org/D123842

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[NVPTX] Enhance vectorization of ld.param & st.param

Since function parameters and return values are passed via param space, we
can force special alignment for values hold in it which will add vecto

[NVPTX] Enhance vectorization of ld.param & st.param

Since function parameters and return values are passed via param space, we
can force special alignment for values hold in it which will add vectorization
options. This change may be done if the function has private or internal
linkage. Special alignment is forced during 2 phases.

1) Instruction selection lowering. Here we use special alignment for function
prototypes (changing both own return value and parameters alignment), call
lowering (changing both callee's return value and parameters alignment).

2) IR pass nvptx-lower-args. Here we change alignment of byval parameters that
belong to param space (or are casted to it). We only handle cases when all
uses of such parameters are loads from it. For such loads, we can change the
alignment according to special type alignment and the load offset. Then,
load-store-vectorizer IR pass will perform vectorization where alignment
allows it.

Special alignment calculated as maximum from default ABI type alignment and
alignment 16. Alignment 16 is chosen because it's the maximum size of
vectorized ld.param & st.param.

Before specifying such special alignment, we should check if it is a multiple
of the alignment that the type already has. For example, if a value has an
enforced alignment of 64, default ABI alignment of 4 and special alignment
of 16, we should preserve 64.

This patch will be followed by a refactoring patch that removes duplicating
code in handling byval and non-byval arguments.

Differential Revision: https://reviews.llvm.org/D120129

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[NVPTX] Enhance vectorization of ld.param & st.param

Since function parameters and return values are passed via param space, we
can force special alignment for values hold in it which will add vecto

[NVPTX] Enhance vectorization of ld.param & st.param

Since function parameters and return values are passed via param space, we
can force special alignment for values hold in it which will add vectorization
options. This change may be done if the function has private or internal
linkage. Special alignment is forced during 2 phases.

1) Instruction selection lowering. Here we use special alignment for function
prototypes (changing both own return value and parameters alignment), call
lowering (changing both callee's return value and parameters alignment).

2) IR pass nvptx-lower-args. Here we change alignment of byval parameters that
belong to param space (or are casted to it). We only handle cases when all
uses of such parameters are loads from it. For such loads, we can change the
alignment according to special type alignment and the load offset. Then,
load-store-vectorizer IR pass will perform vectorization where alignment
allows it.

Special alignment calculated as maximum from default ABI type alignment and
alignment 16. Alignment 16 is chosen because it's the maximum size of
vectorized ld.param & st.param.

Before specifying such special alignment, we should check if it is a multiple
of the alignment that the type already has. For example, if a value has an
enforced alignment of 64, default ABI alignment of 4 and special alignment
of 16, we should preserve 64.

This patch will be followed by a refactoring patch that removes duplicating
code in handling byval and non-byval arguments.

Differential Revision: https://reviews.llvm.org/D121549

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