[PATCH] D134684: [LegalizeTypes][AMDGPU][Mips][RISCV][X86] Mask shift amounts in ExpandShiftWithUnknownAmountBit.

[Craig Topper via Phabricator via llvm-commits]

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If the expanded shift will become a libcall we should not pass
out of range shift amounts that did not exist in the original code.

If we're not making a libcall, an out of bounds shift amount would
produce poison, but the selects would block it from propagating. I
think. Though we didn't freeze the shift amount so I'm really not sure.

It's kind of ugly to detect that we're going to make a libcall at this
stage. We'd need to repeat code from ExpandIntRes_Shift and change the
interface of TLI.shouldExpandShift. For now I've taken the simple
approach and always added the mask. Many of the changed tests are
i128 on a 32-bit target which likely isn't exposed to C language code
other than _BitInt.

Fixes PR57988.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134684

Files:
  llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
  llvm/test/CodeGen/AMDGPU/shift-i128.ll
  llvm/test/CodeGen/Mips/llvm-ir/ashr.ll
  llvm/test/CodeGen/Mips/llvm-ir/lshr.ll
  llvm/test/CodeGen/Mips/llvm-ir/shl.ll
  llvm/test/CodeGen/RISCV/shifts.ll
  llvm/test/CodeGen/SystemZ/shift-12.ll
  llvm/test/CodeGen/X86/scheduler-backtracking.ll
  llvm/test/CodeGen/X86/shift-i128.ll

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