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llvm-project/llvm/test/CodeGen/X86/coalesce-dead-lanes.mir

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[RegisterCoalescer] Do not assert when trying to remat dead values Summary: RegisterCoalescer::reMaterializeTrivialDef used to assert that the input register was live in. But as shown by the new coalesce-dead-lanes.mir test case that seems to be a valid scenario. We now return false instead of the assert, simply avoiding to remat the dead def. Normally a COPY of an undef value is eliminated by eliminateUndefCopy(). Although we only do that when the destination isn't a physical register. So the situation above should be limited to the case when we copy an undef value to a physical register. Reviewers: kparzysz, wmi, tpr Reviewed By: kparzysz Subscribers: MatzeB, qcolombet, tpr, llvm-commits Differential Revision: https://reviews.llvm.org/D50842 llvm-svn: 340255
2018-08-21 15:49:05 +08:00
# RUN: llc -run-pass simple-register-coalescing -O0 -mtriple x86_64-pc-linux-gnu -o - %s | FileCheck %s
---
name: foo
tracksRegLiveness: true
body: |
bb.0:
undef %18.sub_8bit_hi:gr16_abcd = COPY undef $al
%1:gr16_abcd = COPY killed %18
dead %8:gr8 = COPY undef %1.sub_8bit_hi
$al = COPY undef %8
...
# This used to hit an assertion:
# lib/CodeGen/RegisterCoalescer.cpp:1110: RegisterCoalescer::reMaterializeTrivialDef(...): Assertion `ValNo && "CopyMI input register not live"' failed.
#
# CHECK_LABEL: name: foo
# CHECK: bb.0:
# CHECK-NEXT: $al = COPY undef %2:gr8