[llvm-dev] AArch64 global isel

[Jason Eckhardt via llvm-dev]

One problem is that the predicate in your PatFrag is defined in terms of SDNode, which won't work for GISel. Try adding a GISelPredicateCode to do the equivalent test on Machine IR. See also https://llvm.org/docs/GlobalISel/InstructionSelect.html (especially regarding SD imports).

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From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Adrian Tong via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Monday, January 10, 2022 11:33 PM
To: LLVM Developers Mailing List <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] AArch64 global isel

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Hi
I am writing a pattern to select ushr+or into usra on AArch64. I changed the following pattern from add to add_and_or_is_add. One test case test/CodeGen/AArch64/GlobalISel/combine-udiv.ll that uses global isel starts to fail and what was selected into usra is now selected into ushr+add. This only happens in global isel, how can i debug this ?

6471 defm USRA     : SIMDScalarRShiftDTied<   1, 0b00010, "usra",
6472     TriOpFrag<(add_and_or_is_add /* changed from add */ node:$LHS,
6473                    (AArch64vlshr node:$MHS, node:$RHS))>>;

6345 // Match add node and also treat an 'or' node is as an 'add' if the or'ed operands
6346 // have no common bits.
6347 def add_and_or_is_add : PatFrags<(ops node:$lhs, node:$rhs),
6348                          [(add node:$lhs, node:$rhs), (or node:$lhs, node:$rhs)],[{
6349    if (N->getOpcode() == ISD::ADD)
6350      return true;
6351    return CurDAG->haveNoCommonBitsSet(N->getOperand(0), N->getOperand(1));
6352 }]>;

Thanks
-Adrian

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