// Make the FirstSU also dependent on the dependencies of the SecondSU to
// prevent them from being scheduled between the FirstSU and the SecondSU.
- if (&FirstSU != &DAG.EntrySU)
+ if (&FirstSU != &DAG.EntrySU) {
for (const SDep &SI : SecondSU.Preds) {
SUnit *SU = SI.getSUnit();
if (SI.isWeak() || isHazard(SI) || &FirstSU == SU || FirstSU.isSucc(SU))
FirstSU.print(dbgs(), &DAG); dbgs() << '\n';);
DAG.addEdge(&FirstSU, SDep(SU, SDep::Artificial));
}
+ // ExitSU comes last by design, which acts like an implicit dependency
+ // between ExitSU and any bottom root in the graph. We should transfer
+ // this to FirstSU as well.
+ if (&SecondSU == &DAG.ExitSU) {
+ for (SUnit &SU : DAG.SUnits) {
+ if (SU.Succs.empty())
+ DAG.addEdge(&FirstSU, SDep(&SU, SDep::Artificial));
+ }
+ }
+ }
++NumFused;
return true;
--- /dev/null
+# 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
+...