[all-commits] [llvm/llvm-project] 3b4655: [SCEV] Use context instruction for SCEVUnknowns in...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3b46556cb7034409a4bb2566c6d0df7620c56bba
      https://github.com/llvm/llvm-project/commit/3b46556cb7034409a4bb2566c6d0df7620c56bba
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2025-10-14 (Tue, 14 Oct 2025)

  Changed paths:
    M llvm/lib/Analysis/ScalarEvolution.cpp
    M llvm/test/Analysis/ScalarEvolution/trip-multiple-guard-info.ll

  Log Message:
  -----------
  [SCEV] Use context instruction for SCEVUnknowns in getConstantMultiple. (#163260)

Follow-up to https://github.com/llvm/llvm-project/pull/160941.

Even if we don't have a context instruction for the caller, we should be
able to provide context instructions for SCEVUnknowns. Unless I am
missing something, SCEVUnknown only become available at the point their
underlying IR instruction has been defined. If it is an argument, it
should be safe to use the first instruction in the entry block or the
instruction itself if it wraps an instruction.

This allows getConstantMultiple to make better use of alignment
assumptions.

PR: https://github.com/llvm/llvm-project/pull/163260



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