[llvm] [PowerPC] Mask constant operands in ValueBit tracking (PR #67653)

[Qiu Chaofan via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr7 < %s | FileCheck %s --check-prefix=LE64
+; RUN: llc -mtriple=powerpcle-unknown-linux-gnu -mcpu=pwr7 < %s | FileCheck %s --check-prefix=LE32
+; RUN: llc -mtriple=powerpc64-ibm-aix -mcpu=pwr7 < %s | FileCheck %s --check-prefix=BE64
+; RUN: llc -mtriple=powerpc-ibm-aix -mcpu=pwr7 < %s | FileCheck %s --check-prefix=BE32
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ecnelises wrote:

`-mcpu=pwr8` touches another codepath (such instructions are not generated, so only crash on `-mcpu=pwr7`).

The crash comes from constant shift amounts of `srl_parts`, which only presents after splitting `v2i128` into `v1i128` (from the subtraction parts).

https://github.com/llvm/llvm-project/pull/67653