[PATCH] D101472: [RISCV] Teach computeKnownBits that vsetvli returns number less than 2^31.

[Craig Topper via Phabricator via llvm-commits]

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This seems like a reasonable upper bound on VL. WG discussions for
the V spec would probably allow us to use 2^16 as an upper bound
on VLEN, but this is good enough for now.

This allows us to remove sext and zext if user happens to assign
the size_t result into an int and then uses it as a VL intrinsic
argument which is size_t.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101472

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/test/CodeGen/RISCV/rvv/vsetvl-ext.ll
  llvm/test/Transforms/InstCombine/RISCV/lit.local.cfg
  llvm/test/Transforms/InstCombine/RISCV/riscv-vsetvli-knownbits.ll

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