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834ee28da9
Summary:
This pass sinks COPY instructions into a successor block, if the COPY is not
used in the current block and the COPY is live-in to a single successor
(i.e., doesn't require the COPY to be duplicated). This avoids executing the
the copy on paths where their results aren't needed. This also exposes
additional opportunites for dead copy elimination and shrink wrapping.
These copies were either not handled by or are inserted after the MachineSink
pass. As an example of the former case, the MachineSink pass cannot sink
COPY instructions with allocatable source registers; for AArch64 these type
of copy instructions are frequently used to move function parameters (PhyReg)
into virtual registers in the entry block..
For the machine IR below, this pass will sink %w19 in the entry into its
successor (%bb.1) because %w19 is only live-in in %bb.1.
```
%bb.0:
%wzr = SUBSWri %w1, 1
%w19 = COPY %w0
Bcc 11, %bb.2
%bb.1:
Live Ins: %w19
BL @fun
%w0 = ADDWrr %w0, %w19
RET %w0
%bb.2:
%w0 = COPY %wzr
RET %w0
```
As we sink %w19 (CSR in AArch64) into %bb.1, the shrink-wrapping pass will be
able to see %bb.0 as a candidate.
With this change I observed 12% more shrink-wrapping candidate and 13% more dead copies deleted in spec2000/2006/2017 on AArch64.
Reviewers: qcolombet, MatzeB, thegameg, mcrosier, gberry, hfinkel, john.brawn, twoh, RKSimon, sebpop, kparzysz
Reviewed By: sebpop
Subscribers: evandro, sebpop, sfertile, aemerson, mgorny, javed.absar, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D41463
llvm-svn: 328237
366 lines
7.2 KiB
YAML
366 lines
7.2 KiB
YAML
# RUN: llc -mtriple=aarch64-none-linux-gnu -run-pass=postra-machine-sink -verify-machineinstrs -o - %s | FileCheck %s
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---
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# Sink w19 to %bb.1.
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# CHECK-LABEL: name: sinkcopy1
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# CHECK-LABEL: bb.0:
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# CHECK-NOT: $w19 = COPY killed $w0
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# CHECK-LABEL: bb.1:
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# CHECK: liveins: $w1, $w0
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# CHECK: renamable $w19 = COPY killed $w0
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name: sinkcopy1
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY killed $w0
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Bcc 11, %bb.1, implicit $nzcv
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B %bb.2
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bb.1:
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liveins: $w1, $w19
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$w0 = ADDWrr $w1, $w19
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RET $x0
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bb.2:
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$w0 = COPY $wzr
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RET $x0
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...
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---
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# Sink w19 to %bb.2.
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# CHECK-LABEL: name: sinkcopy2
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# CHECK-LABEL: bb.0:
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# CHECK-NOT: renamable $w19 = COPY killed $w0
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# CHECK-LABEL: bb.2:
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# CHECK: liveins: $w1, $w0
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# CHECK: renamable $w19 = COPY killed $w0
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name: sinkcopy2
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY killed $w0
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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$w0 = COPY $wzr
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RET $x0
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bb.2:
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liveins: $w1, $w19
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$w0 = ADDWrr $w1, $w19
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RET $x0
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...
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---
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# Sink w19 and w20 to %bb.1.
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# CHECK-LABEL: name: sinkcopy3
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# CHECK-LABEL: bb.0:
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# CHECK-NOT: renamable $w19 = COPY killed $w0
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# CHECK-LABEL: bb.1:
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# CHECK: liveins: $w1, $w0
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# CHECK: renamable $w19 = COPY killed $w0
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# CHECK: renamable $w20 = COPY killed $w1
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name: sinkcopy3
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY killed $w0
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renamable $w20 = COPY killed $w1
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bb.1:
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liveins: $w19, $w20
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$w0 = COPY $w19
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$w1 = COPY $w20
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RET $x0
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...
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# Sink w19 to %bb.1 and w20 to %bb.2.
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# CHECK-LABEL: name: sinkcopy4
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# CHECK-LABEL: bb.0:
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# CHECK-NOT: renamable $w19 = COPY killed $w0
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# CHECK-NOT: renamable $w20 = COPY killed $w1
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# CHECK-LABEL: bb.1:
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# CHECK: liveins: $w1, $w0
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# CHECK: renamable $w19 = COPY killed $w0
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# CHECK-LABEL: bb.2:
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# CHECK: liveins: $w0, $w1
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# CHECK: renamable $w20 = COPY killed $w1
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name: sinkcopy4
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY killed $w0
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renamable $w20 = COPY killed $w1
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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liveins: $w1, $w19
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$w0 = ADDWrr $w1, $w19
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RET $x0
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bb.2:
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liveins: $w0, $w20
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$w0 = ADDWrr $w0, $w20
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RET $x0
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...
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# Sink w19 to %bb.3 through %bb.2.
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# CHECK-LABEL: name: sinkcopy5
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# CHECK-LABEL: bb.0:
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# CHECK-NOT: renamable $w19 = COPY $w0
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# CHECK-LABEL: bb.2:
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# CHECK: $w1 = ADDWrr $w1, $w0
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# CHECK-LABEL: bb.3:
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# CHECK: liveins: $w1, $w0
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# CHECK: renamable $w19 = COPY killed $w0
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name: sinkcopy5
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY $w0
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Bcc 11, %bb.2, implicit $nzcv
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bb.1:
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liveins: $x0
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$w19 = COPY $wzr
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RET $x0
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bb.2:
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liveins: $w0, $w1, $w19
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$w1 = ADDWrr $w1, killed $w0
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bb.3:
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liveins: $w1, $w19
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$w0 = ADDWrr $w1, $w19
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RET $x0
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...
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# Sink w19 to %bb.3, but through %bb.2.
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# CHECK-LABEL: name: sinkcopy6
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# CHECK-LABEL: bb.0:
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# CHECK-NOT: renamable $w19 = COPY $w0
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# CHECK-NOT: renamable $w20 = COPY $w0
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# CHECK-LABEL: bb.2:
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# CHECK: liveins: $w1, $w0
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# CHECK: renamable $w19 = COPY $w0
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# CHECK: renamable $w20 = COPY $w19
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name: sinkcopy6
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY $w0
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renamable $w20 = COPY $w19
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Bcc 11, %bb.2, implicit $nzcv
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bb.1:
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$w0 = COPY $wzr
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RET $x0
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bb.2:
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liveins: $w1, $w20
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$w0 = ADDWrr killed $w1, $w20
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RET $x0
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...
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---
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# Sink w19 regardless of the def of wzr in bb.0.
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# CHECK-LABEL: name: sinkcopy7
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# CHECK-LABEL: bb.0:
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# CHECK-NOT: renamable $w19 = COPY $w0
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# CHECK-LABEL: bb.2:
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# CHECK: renamable $w19 = COPY $wzr
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name: sinkcopy7
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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renamable $w19 = COPY $wzr
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$wzr = SUBSWri $w1, 1, 0, implicit-def $nzcv
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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$x0 = COPY $xzr
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RET $x0
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bb.2:
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liveins: $w0, $w19
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$w0 = ADDWrr $w0, $w19
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RET $x0
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---
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# Don't sink w19 as w0 is defined in bb.0.
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# CHECK-LABEL: name: donotsinkcopy1
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# CHECK-LABEL: bb.0:
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# CHECK: renamable $w19 = COPY $w0
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# CHECK: $w0 = LDRWui $sp, 0
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name: donotsinkcopy1
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY $w0
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$w0 = LDRWui $sp, 0 :: (load 4)
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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$x0 = COPY $xzr
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RET $x0
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bb.2:
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liveins: $w0, $w19
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$w0 = ADDWrr $w0, $w19
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RET $x0
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...
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---
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# Don't sink w19 as w19 is used in bb.0.
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# CHECK-LABEL: name: donotsinkcopy2
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# CHECK-LABEL: bb.0:
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# CHECK: renamable $w19 = COPY $w0
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# CHECK: STRWui $w1, $x19, 0
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name: donotsinkcopy2
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY $w0
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STRWui $w1, $x19, 0 :: (store 4)
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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$x0 = COPY $xzr
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RET $x0
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bb.2:
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liveins: $w0, $w19
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$w0 = ADDWrr $w0, $w19
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RET $x0
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...
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---
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# Don't sink w19 as w19 is used in both %bb.1 and %bb.2.
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# CHECK-LABEL: name: donotsinkcopy3
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# CHECK-LABEL: bb.0:
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# CHECK: renamable $w19 = COPY $w0
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name: donotsinkcopy3
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY $w0
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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liveins: $w19
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$w0 = COPY $w19
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RET $x0
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bb.2:
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liveins: $w0, $w19
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$w0 = ADDWrr $w0, $w19
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RET $x0
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...
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---
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# Don't sink w19 as %bb.2 has multiple predecessors.
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# CHECK-LABEL: name: donotsinkcopy4
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# CHECK-LABEL: bb.0:
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# CHECK: renamable $w19 = COPY $w0
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name: donotsinkcopy4
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY $w0
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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liveins: $w0
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$w19 = COPY $w0
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B %bb.2
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bb.2:
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liveins: $w0, $w19
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$w0 = ADDWrr $w0, $w19
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RET $x0
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...
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# Don't sink w19 after sinking w20.
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# CHECK-LABEL: name: donotsinkcopy5
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# CHECK-LABEL: bb.0:
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# CHECK: renamable $w19 = COPY $w0
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# CHECK-LABEL: bb.2:
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# CHECK: liveins: $w0, $w19
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# CHECK: renamable $w20 = COPY $w19
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name: donotsinkcopy5
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $w0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $w19 = COPY $w0
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renamable $w20 = COPY $w19
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Bcc 11, %bb.2, implicit $nzcv
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bb.1:
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liveins: $w19
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$w0 = COPY $w19
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RET $x0
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bb.2:
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liveins: $w0, $w20
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$w0 = ADDWrr killed $w0, $w20
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RET $x0
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...
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---
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# Don't sink w19 as x19 is live-in in %bb.2.
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# CHECK-LABEL: name: donotsinkcopy6
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# CHECK-LABEL: bb.0:
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name: donotsinkcopy6
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $x0, $w1
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$w1 = SUBSWri $w1, 1, 0, implicit-def $nzcv
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renamable $x19 = COPY $x0
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Bcc 11, %bb.2, implicit $nzcv
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B %bb.1
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bb.1:
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liveins: $w19
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$w0 = COPY $w19
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RET $x0
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bb.2:
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liveins: $x0, $x19
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$x0 = ADDXrr $x0, $x19
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RET $x0
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...
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