[all-commits] [llvm/llvm-project] d99068: [CIR] Implement ArgKind::Expand in CallConvLowerin...

[adams381 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d9906882fc613471ab51e7185094efae893066de
      https://github.com/llvm/llvm-project/commit/d9906882fc613471ab51e7185094efae893066de
  Author: adams381 <adams at nvidia.com>
  Date:   2026-06-25 (Thu, 25 Jun 2026)

  Changed paths:
    M clang/lib/CIR/Dialect/Transforms/TargetLowering/CIRABIRewriteContext.cpp
    M clang/lib/CIR/Dialect/Transforms/TargetLowering/CIRABIRewriteContext.h
    A clang/test/CIR/Transforms/abi-lowering/expand-struct-arg.cir

  Log Message:
  -----------
  [CIR] Implement ArgKind::Expand in CallConvLowering (#201718)

ArgKind::Expand classifies a struct argument for flattening: each field
becomes a separate scalar argument at the ABI level.  Classic CodeGen
calls this "struct expansion" — used on targets like MIPS and some ARM
calling conventions.

CIRABIRewriteContext previously emitted errorNYI at both classification
sites.  The replacement covers three call paths.  In buildNewArgTypes,
the original struct type is replaced by one wire type per field.  In
insertArgCoercion, the single struct block argument is replaced by N
scalar block arguments and an alloca+get_member+store+load sequence at
the entry block reassembles them for body uses; a running block-argument
index (rather than classIdx + sretOffset) correctly tracks the expanded
slot count when multiple Expand args or sret+Expand combinations appear.
The Ignore-drop loop gains a classToBlockArg pre-computation so that
Ignore args following Expand args are erased at the correct index.  In
rewriteCallSite, cir.extract_member decomposes the struct operand into
its constituent fields, which become separate call arguments.

Asserts guard the two structural invariants: Expand requires a struct
type (not a union) and at least one field.



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