[PATCH] D88539: [PowerPC] Handle the constant with many trailing ones.

[EsmeYi via Phabricator via llvm-commits]

Esme created this revision.
Esme added reviewers: jsji, nemanjai, steven.zhang, lkail, shchenz, qiucf, PowerPC.
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Esme requested review of this revision.

We have handled the constants with many trailing zeros like `i64 5228199936` ( 0b100110111101000000000000000000000) , which can be materialized by 2 instructions:

  	li 3, 2493
  	sldi 3, 3, 21

Inspired by this, we considered another case where the constant has many trailing ones. We can take advantage of li/lis's sign-extension to generate leading ones, and then mask extra bits off after rotation.
For example, without such ISEL pattern we need 4 instructions to materialize `i64 10460594175` (0b1001101111011111111111111111111111)

  	li 3, 2
  	sldi 3, 3, 32
  	oris 3, 3, 28543
  	ori 3, 3, 65535

Now we only need 2 instructions after this patch:

  	li 3, -31522
  	rldicl 3, 3, 23, 30


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D88539

Files:
  llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
  llvm/test/CodeGen/PowerPC/combine_ext_trunc.ll
  llvm/test/CodeGen/PowerPC/constants-i64.ll
  llvm/test/CodeGen/PowerPC/negctr.ll
  llvm/test/CodeGen/PowerPC/ori_imm64.ll

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