[SelectionDAG] Make fast and linearize visible by clang -pre-RA-sched

[TaoPan]

Summary

ScheduleDAGFast.cpp is compiled to object file, but the ScheduleDAGFast
object file isn't linked into clang executable file as no symbol is
referred by outside. Add calling to createXxx of ScheduleDAGFast.cpp,
then the ScheduleDAGFast object file will be linked into clang
executable file. The static RegisterScheduler will register scheduler
fast and linearize at clang boot time.

[TaoPan]

Could you please have a review?

[pengfei]

clang/test/CodeGen/pre-ra-sched.c

1

Should we add test under llvm/test? A bit strange that changing LLVM code while adding test in clang/test.

llvm/include/llvm/CodeGen/TargetLowering.h

105

This comma should be removed.

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

273–276

I saw they are always registered in ScheduleDAGFast.cpp:
https://github.com/llvm/llvm-project/blob/main/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp#L36
Why do we register them again here?

[TaoPan]

Move test from clang/test to llvm/test, remove comma of the last enum item.

[TaoPan]

Thanks Pengfei for your review comments!

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

273–276

Please also help to have a review of the Summary. It's a little bit of a trick. ScheduleDAGFast.cpp is compiled to object file, but the object file isn't linked into clang executable file as no symbol is referred by outside without this patch.

[TaoPan]

git rebase

[craig.topper]

llvm/test/CodeGen/Generic/pre-ra-sched.c

1 ↗

(On Diff #343598)

You can't run clang from an llvm test directory. There's no guarantee clang will have been compiled.

[craig.topper]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

273–276

That wasn't very clear from your summary. The "the object file isn't linked into clang executable file as no symbol is referred by outside without this patch" in this comment was much more help. Can you put something like that in summary?

Why are they being stripped from clang but not llc?

[craig.topper]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

273–276

Oh I see, llc uses include/llvm/CodeGen/LinkAllCodegenComponents.h to force these to link in.

[TaoPan]

Move test back to clang/test/CodeGen/

[TaoPan]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

273–276

Thanks! I modified summary. could you please have a review?
Yes, you are right, llc include LinkAllCodegenComponents.h which refers function createFastDAGScheduler of ScheduleDAGFast.cpp.

llvm/test/CodeGen/Generic/pre-ra-sched.c

1 ↗

(On Diff #343598)

Thanks for notifying no guarantee clang in llvm test directory! I moved the test back to clang/test/CodeGen/.

[pengfei]

I see. LGTM, but let's wait one or more days to see if others object it.

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

275–276

Can this be omitted given createFastDAGScheduler should make it linked.

[TaoPan]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

275–276

For making scheduler fast and linearize visible by clang -pre-RA-sched, yes, createDAGLinearizer can be omitted.
Adding both is also for keeping the ability that all schedulers can be selected by TargetLowering object in the case of clang -pre-RA-sched=default.

[hubert.reinterpretcast]

clang/test/CodeGen/pre-ra-sched.c

2–3

The test as was committed is bogus. It checks the output binary(!) stream for an error message when stderr was not even redirected. Please fix.

[hubert.reinterpretcast]

clang/test/CodeGen/pre-ra-sched.c

2–3

Fix committed: https://github.com/llvm/llvm-project/commit/603818b97c795114f66a6fc13e8a5f0e54b49a13

[TaoPan]

clang/test/CodeGen/pre-ra-sched.c

2–3

Thanks for your review comment and fixing!
I tried to check stderr as you guided and meet empty stdin problem, thanks for your quick fixing and I got FileCheck option --allow-empty can resolve this kind of problem.

[hubert.reinterpretcast]

clang/test/CodeGen/pre-ra-sched.c

2–3

No problem. Thanks for looking into it.

clang/test/CodeGen/pre-ra-sched.c

+// RUN: %clang %s -mllvm -pre-RA-sched=fast -c -o - | FileCheck %s
+// RUN: %clang %s -mllvm -pre-RA-sched=linearize -c -o - | FileCheck %s
+
+// CHECK-NOT: clang (LLVM option parsing): for the --pre-RA-sched option: Cannot find option named
+
+int main() {
+  return 0;
+}

llvm/include/llvm/CodeGen/TargetLowering.h

 class TargetMachine;
 class TargetRegisterClass;
 class TargetRegisterInfo;
 class TargetTransformInfo;
 class Value;
 
 namespace Sched {
 
-  enum Preference {
-    None,             // No preference
-    Source,           // Follow source order.
-    RegPressure,      // Scheduling for lowest register pressure.
-    Hybrid,           // Scheduling for both latency and register pressure.
-    ILP,              // Scheduling for ILP in low register pressure mode.
-    VLIW              // Scheduling for VLIW targets.
-  };
+  None,        // No preference
+  Source,      // Follow source order.
+  RegPressure, // Scheduling for lowest register pressure.
+  Hybrid,      // Scheduling for both latency and register pressure.
+  ILP,         // Scheduling for ILP in low register pressure mode.
+  VLIW,        // Scheduling for VLIW targets.
+  Fast,        // Fast suboptimal list scheduling
+  Linearize,   // Linearize DAG, no scheduling
 
 } // end namespace Sched
 
 // MemOp models a memory operation, either memset or memcpy/memmove.
 struct MemOp {
 private:
   // Shared
   uint64_t Size;

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

if (OptLevel == CodeGenOpt::None ||
         TLI->getSchedulingPreference() == Sched::Source)
       return createSourceListDAGScheduler(IS, OptLevel);
     if (TLI->getSchedulingPreference() == Sched::RegPressure)
       return createBURRListDAGScheduler(IS, OptLevel);
     if (TLI->getSchedulingPreference() == Sched::Hybrid)
       return createHybridListDAGScheduler(IS, OptLevel);
     if (TLI->getSchedulingPreference() == Sched::VLIW)
       return createVLIWDAGScheduler(IS, OptLevel);
+    if (TLI->getSchedulingPreference() == Sched::Fast)
+      return createFastDAGScheduler(IS, OptLevel);
+    if (TLI->getSchedulingPreference() == Sched::Linearize)
+      return createDAGLinearizer(IS, OptLevel);
     assert(TLI->getSchedulingPreference() == Sched::ILP &&
            "Unknown sched type!");
     return createILPListDAGScheduler(IS, OptLevel);
   }
 
 } // end namespace llvm
 
 // EmitInstrWithCustomInserter - This method should be implemented by targets