[all-commits] [llvm/llvm-project] 5083e8: Folding extract_strided_metadata input into reinte...

[ivangarcia44 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5083e80c14a5c1f0ab40b5df95771ebbdda1adb2
      https://github.com/llvm/llvm-project/commit/5083e80c14a5c1f0ab40b5df95771ebbdda1adb2
  Author: ivangarcia44 <36650061+ivangarcia44 at users.noreply.github.com>
  Date:   2025-04-09 (Wed, 09 Apr 2025)

  Changed paths:
    M mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
    M mlir/test/Dialect/MemRef/canonicalize.mlir

  Log Message:
  -----------
  Folding extract_strided_metadata input into reinterpret_cast (#134845)

We can always fold the input of a extract_strided_metadata operator to
the input of a reinterpret_cast operator, because they point to the same
memory. Note that the reinterpret_cast does not use the layout of its
input memref, only its base memory pointer which is the same as the base
pointer returned by the extract_strided_metadata operator and the base
pointer of the extract_strided_metadata memref input.

Operations like expand_shape, collapse_shape, and subview are lowered to
a pair of extract_strided_metadata and reinterpret_cast like this:
      
%base_buffer, %offset, %sizes:2, %strides:2 =
memref.extract_strided_metadata %input_memref :
memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index,
index

%reinterpret_cast = memref.reinterpret_cast %base_buffer to offset:
[%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<f32> to
memref<OD1x...xODNxBaseType >

In many cases the input of the extract_strided_metadata input can be
passed directly into the input of the reinterpret_cast operation like
this (see how %base_buffer is replaced by %input_memref in the
reinterpret_cast above and the input type is updated):

%base_buffer, %offset, %sizes:2, %strides:2 =
memref.extract_strided_metadata %input_memref :
memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index,
index
%reinterpret_cast = memref.reinterpret_cast %input_memref to offset:
[%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] :
memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType >

When dealing with static dimensions, the extract_strided_metatdata will
become deadcode and we end up only with a reinterpret_cast:

%reinterpret_cast = memref.reinterpret_cast %input_memref to offset:
[%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] :
memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType >

Note that reinterpret_cast only reads the base memory pointer from the
input memref (%input_memref above), which is equivalent to the
%base_buffer returned by the extract_strided_metadata operation. Hence
it is legal always to use the extract_strided_metadata input memref
directly in the reinterpret_cast. Note that since this is a pointer,
this operation is legal even when the base pointer values are modified
between the operation pair.

@matthias-springer 
@joker-eph 
@sahas3
@Hanumanth04
@dixinzhou
@rafaelubalmw

---------

Co-authored-by: Ivan Garcia <igarcia at vdi-ah2ddp-178.dhcp.mathworks.com>



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications