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2c06ea1b59
When fusing instructions A and B, we must add all predecessors of B as predecessors of A to avoid instructions getting scheduling in between. There is a special case involving ExitSU: Every other node must be scheduled before it by design and we don't need to make this explicit in the graph, however when fusing with a different node we need to schedule every othere node before the fused node too and we need to make this explicit now: This patch adds a dependency from the fused node to all roots in the graph. Differential Revision: https://reviews.llvm.org/D49830 llvm-svn: 338046
29 lines
1.0 KiB
YAML
29 lines
1.0 KiB
YAML
# RUN: llc -o - %s -mtriple=aarch64-- -mattr=+arith-bcc-fusion -run-pass postmisched | FileCheck %s --check-prefixes=CHECK,FUSION
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# RUN: llc -o - %s -mtriple=aarch64-- -mattr=-arith-bcc-fusion -run-pass postmisched | FileCheck %s --check-prefixes=CHECK,NOFUSION
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# Make sure the last instruction is correctly macro-fused when scheduling
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# top-down (post-ra).
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---
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# CHECK-LABEL: name: fuse_last
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# CHECK: $x1 = LDRXui $x0, 0
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# NOFUSION: $xzr = SUBSXri killed $x2, 0, 0, implicit-def $nzcv
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# CHECK: STRXui killed $x0, killed $x1, 0
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# FUSION: $xzr = SUBSXri killed $x2, 0, 0, implicit-def $nzcv
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# CHECK: Bcc 1, %bb.1, implicit killed $nzcv
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name: fuse_last
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $x0, $x2
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$x1 = LDRXui $x0, 0
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; There is latency between these two instructions tempting the scheduler to
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; move the SUBSXri in between them. However doing so breaks macro fusion.
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STRXui $x0, $x1, 0
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$xzr = SUBSXri $x2, 0, 0, implicit-def $nzcv
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Bcc 1, %bb.1, implicit killed $nzcv
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bb.1:
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RET_ReallyLR implicit undef $x0
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...
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