llvm-mirror/test/CodeGen/AArch64/macro-fusion-last.mir
Matthias Braun 2c06ea1b59 MacroFusion: Fix macro fusion with ExitSU failing in top-down scheduling
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
2018-07-26 17:43:56 +00:00

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
# RUN: llc -o - %s -mtriple=aarch64-- -mattr=-arith-bcc-fusion -run-pass postmisched | FileCheck %s --check-prefixes=CHECK,NOFUSION
# Make sure the last instruction is correctly macro-fused when scheduling
# top-down (post-ra).
---
# CHECK-LABEL: name: fuse_last
# CHECK: $x1 = LDRXui $x0, 0
# NOFUSION: $xzr = SUBSXri killed $x2, 0, 0, implicit-def $nzcv
# CHECK: STRXui killed $x0, killed $x1, 0
# FUSION: $xzr = SUBSXri killed $x2, 0, 0, implicit-def $nzcv
# CHECK: Bcc 1, %bb.1, implicit killed $nzcv
name: fuse_last
tracksRegLiveness: true
body: |
bb.0:
liveins: $x0, $x2
$x1 = LDRXui $x0, 0
; There is latency between these two instructions tempting the scheduler to
; move the SUBSXri in between them. However doing so breaks macro fusion.
STRXui $x0, $x1, 0
$xzr = SUBSXri $x2, 0, 0, implicit-def $nzcv
Bcc 1, %bb.1, implicit killed $nzcv
bb.1:
RET_ReallyLR implicit undef $x0
...