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The ABI allows sub-128 vectors to be passed and returned in registers,
with the vector occupying the upper part of a register. We therefore
want to legalize those types by widening the vector rather than promoting
the elements.
The patch includes some simple tests for sub-128 vectors and also tests
that we can recognize various pack sequences, some of which use sub-128
vectors as temporary results. One of these forms is based on the pack
sequences generated by llvmpipe when no intrinsics are used.
Signed unpacks are recognized as BUILD_VECTORs whose elements are
individually sign-extended. Unsigned unpacks can have the equivalent
form with zero extension, but they also occur as shuffles in which some
elements are zero.
Based on a patch by Richard Sandiford.
llvm-svn: 236525
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This the first of a series of patches to add CodeGen support exploiting
the instructions of the z13 vector facility. This patch adds support
for the native integer vector types (v16i8, v8i16, v4i32, v2i64).
When the vector facility is present, we default to the new vector ABI.
This is characterized by two major differences:
- Vector types are passed/returned in vector registers
(except for unnamed arguments of a variable-argument list function).
- Vector types are at most 8-byte aligned.
The reason for the choice of 8-byte vector alignment is that the hardware
is able to efficiently load vectors at 8-byte alignment, and the ABI only
guarantees 8-byte alignment of the stack pointer, so requiring any higher
alignment for vectors would require dynamic stack re-alignment code.
However, for compatibility with old code that may use vector types, when
*not* using the vector facility, the old alignment rules (vector types
are naturally aligned) remain in use.
These alignment rules are not only implemented at the C language level
(implemented in clang), but also at the LLVM IR level. This is done
by selecting a different DataLayout string depending on whether the
vector ABI is in effect or not.
Based on a patch by Richard Sandiford.
llvm-svn: 236521
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