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When reusing a register for a new definition, the fast register allocator used to insert a kill flag at the previous last use of that register to inform later passes that this register is free between the redef and the last use. However, this may be wrong when subregisters are involved. Indeed, a partially redef would have trigger a kill of the full super register, potentially wrongly marking all the other subregisters as free. Given we don't track which lanes are still live, we cannot set the kill flag in such case. Note: This bug has been latent for about 7 years (r104056). llvmg.org/PR33677 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307428 91177308-0d34-0410-b5e6-96231b3b80d8
35 lines
942 B
YAML
35 lines
942 B
YAML
# RUN: llc -verify-machineinstrs -run-pass regallocfast -mtriple s390x-ibm-linux -o - %s | FileCheck %s
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--- |
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@g_167 = external global [5 x i64], align 8
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define void @main() local_unnamed_addr {
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ret void
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}
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...
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# Make sure the usage of different subregisters on the same virtual register
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# does not result in invalid kill flags.
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# PR33677
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---
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name: main
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alignment: 2
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tracksRegLiveness: true
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registers:
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- { id: 0, class: gr128bit }
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- { id: 1, class: gr64bit }
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- { id: 2, class: addr64bit }
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# CHECK: %r0q = L128
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# CHECK-NEXT: %r0l = COPY %r1l
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# Although R0L partially redefines R0Q, it must not mark R0Q as kill
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# because R1D is still live through that instruction.
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# CHECK-NOT: %r0q<imp-use,kill>
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# CHECK-NEXT: %r2d = COPY %r1d
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# CHECK-NEXT: LARL
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body: |
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bb.0:
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%0.subreg_hl32 = COPY %0.subreg_l32
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%1 = COPY %0.subreg_l64
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%2 = LARL @g_167
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STC %1.subreg_l32, %2, 8, _
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...
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