[llvm] 98265db - [ScheduleDAG] Support REQ_SEQUENCE unscheduling

[Filipp Zhinkin via llvm-commits]

Author: Filipp Zhinkin
Date: 2022-12-30T15:17:11+04:00
New Revision: 98265db84c332a6969b0ca10031f175f2af731fa

URL: https://github.com/llvm/llvm-project/commit/98265db84c332a6969b0ca10031f175f2af731fa
DIFF: https://github.com/llvm/llvm-project/commit/98265db84c332a6969b0ca10031f175f2af731fa.diff

LOG: [ScheduleDAG] Support REQ_SEQUENCE unscheduling

REG_SEQUENCE node requires special treatment during the
unscheduling because the node is untyped and neither its
class, nor cost could be retrieved the same way as for
typed nodes.

Related issue: https://github.com/llvm/llvm-project/issues/58911

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D138837

Added: 
    llvm/test/CodeGen/ARM/unschedule-reg-sequence.ll

Modified: 
    llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index 0be11b61f7b4e..c573e3d4dfe6a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -302,6 +302,8 @@ class ScheduleDAGRRList : public ScheduleDAGSDNodes {
 
 }  // end anonymous namespace
 
+static constexpr unsigned RegSequenceCost = 1;
+
 /// GetCostForDef - Looks up the register class and cost for a given definition.
 /// Typically this just means looking up the representative register class,
 /// but for untyped values (MVT::Untyped) it means inspecting the node's
@@ -333,7 +335,7 @@ static void GetCostForDef(const ScheduleDAGSDNodes::RegDefIter &RegDefPos,
       unsigned DstRCIdx = cast<ConstantSDNode>(Node->getOperand(0))->getZExtValue();
       const TargetRegisterClass *RC = TRI->getRegClass(DstRCIdx);
       RegClass = RC->getID();
-      Cost = 1;
+      Cost = RegSequenceCost;
       return;
     }
 
@@ -2302,6 +2304,16 @@ void RegReductionPQBase::unscheduledNode(SUnit *SU) {
       RegPressure[RCId] += TLI->getRepRegClassCostFor(VT);
       continue;
     }
+    if (POpc == TargetOpcode::REG_SEQUENCE) {
+      unsigned DstRCIdx =
+          cast<ConstantSDNode>(PN->getOperand(0))->getZExtValue();
+      const TargetRegisterClass *RC = TRI->getRegClass(DstRCIdx);
+      unsigned RCId = RC->getID();
+      // REG_SEQUENCE is untyped, so getRepRegClassCostFor could not be used
+      // here. Instead use the same constant as in GetCostForDef.
+      RegPressure[RCId] += RegSequenceCost;
+      continue;
+    }
     unsigned NumDefs = TII->get(PN->getMachineOpcode()).getNumDefs();
     for (unsigned i = 0; i != NumDefs; ++i) {
       MVT VT = PN->getSimpleValueType(i);

diff  --git a/llvm/test/CodeGen/ARM/unschedule-reg-sequence.ll b/llvm/test/CodeGen/ARM/unschedule-reg-sequence.ll
new file mode 100644
index 0000000000000..37ba34e1699dc
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/unschedule-reg-sequence.ll
@@ -0,0 +1,21 @@
+; RUN: llc -verify-machineinstrs < %s
+; Regression test for https://github.com/llvm/llvm-project/issues/58911
+
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7-none-unknown-eabi"
+
+ at a = dso_local global i64 0, align 8
+ at d = dso_local local_unnamed_addr global i32 0, align 4
+
+define dso_local void @f() nounwind {
+entry:
+  store volatile i64 0, ptr @a, align 8
+  %0 = load i32, ptr @d, align 4
+  %tobool.not = icmp eq i32 %0, 0
+  %conv = zext i32 %0 to i64
+  %sub = sub nsw i64 0, %conv
+  %cond = select i1 %tobool.not, i64 0, i64 %sub
+  store volatile i64 %cond, ptr @a, align 8
+  ret void
+}
+