Analyze all candidates

Author: svs-quic

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -3015,30 +3015,25 @@ static bool cannotInsertTailCall(const MachineBasicBlock &MBB) {
   return false;
 }
 
-static std::optional<MachineOutlinerConstructionID>
-analyzeCandidate(outliner::Candidate &C) {
+static bool analyzeCandidate(outliner::Candidate &C) {
   // If last instruction is return then we can rely on
   // the verification already performed in the getOutliningTypeImpl.
   if (C.back().isReturn()) {
     assert(!cannotInsertTailCall(*C.getMBB()) &&
            "The candidate who uses return instruction must be outlined "
            "using tail call");
-    return MachineOutlinerTailCall;
+    return false;
   }
 
-  auto CandidateUsesX5 = [](outliner::Candidate &C) {
-    const TargetRegisterInfo *TRI = C.getMF()->getSubtarget().getRegisterInfo();
-    if (std::any_of(C.begin(), C.end(), [TRI](const MachineInstr &MI) {
-          return isMIModifiesReg(MI, TRI, RISCV::X5);
-        }))
-      return true;
-    return !C.isAvailableAcrossAndOutOfSeq(RISCV::X5, *TRI);
-  };
-
-  if (!CandidateUsesX5(C))
-    return MachineOutlinerDefault;
+  // Filter out candidates where the X5 register (t0) can't be used to setup
+  // the function call.
+  const TargetRegisterInfo *TRI = C.getMF()->getSubtarget().getRegisterInfo();
+  if (std::any_of(C.begin(), C.end(), [TRI](const MachineInstr &MI) {
+        return isMIModifiesReg(MI, TRI, RISCV::X5);
+      }))
+    return true;
 
-  return std::nullopt;
+  return !C.isAvailableAcrossAndOutOfSeq(RISCV::X5, *TRI);
 }
 
 std::optional<std::unique_ptr<outliner::OutlinedFunction>>
@@ -3047,35 +3042,32 @@ RISCVInstrInfo::getOutliningCandidateInfo(
     std::vector<outliner::Candidate> &RepeatedSequenceLocs,
     unsigned MinRepeats) const {
 
-  // Each RepeatedSequenceLoc is identical.
-  outliner::Candidate &Candidate = RepeatedSequenceLocs[0];
-  auto CandidateInfo = analyzeCandidate(Candidate);
-  if (!CandidateInfo)
-    RepeatedSequenceLocs.clear();
+  // Analyze each candidate and erase the ones that are not viable.
+  llvm::erase_if(RepeatedSequenceLocs, analyzeCandidate);
 
   // If the sequence doesn't have enough candidates left, then we're done.
   if (RepeatedSequenceLocs.size() < MinRepeats)
     return std::nullopt;
 
+  // Each RepeatedSequenceLoc is identical.
+  outliner::Candidate &Candidate = RepeatedSequenceLocs[0];
   unsigned InstrSizeCExt =
       Candidate.getMF()->getSubtarget<RISCVSubtarget>().hasStdExtCOrZca() ? 2
                                                                           : 4;
   unsigned CallOverhead = 0, FrameOverhead = 0;
 
-  MachineOutlinerConstructionID MOCI = CandidateInfo.value();
-  switch (MOCI) {
-  case MachineOutlinerDefault:
-    // call t0, function = 8 bytes.
-    CallOverhead = 8;
-    // jr t0 = 4 bytes, 2 bytes if compressed instructions are enabled.
-    FrameOverhead = InstrSizeCExt;
-    break;
-  case MachineOutlinerTailCall:
+  MachineOutlinerConstructionID MOCI = MachineOutlinerDefault;
+  if (Candidate.back().isReturn()) {
+    MOCI = MachineOutlinerTailCall;
     // tail call = auipc + jalr in the worst case without linker relaxation.
     CallOverhead = 4 + InstrSizeCExt;
     // Using tail call we move ret instruction from caller to callee.
     FrameOverhead = 0;
-    break;
+  } else {
+    // call t0, function = 8 bytes.
+    CallOverhead = 8;
+    // jr t0 = 4 bytes, 2 bytes if compressed instructions are enabled.
+    FrameOverhead = InstrSizeCExt;
   }
 
   for (auto &C : RepeatedSequenceLocs)

llvm/test/CodeGen/RISCV/machine-outliner-call-x5-liveout.mir

@@ -53,7 +53,10 @@ body:             |
   ; RV32I-MO: bb.0:
   ; RV32I-MO-NEXT:   liveins: $x10, $x11
   ; RV32I-MO-NEXT: {{  $}}
-  ; RV32I-MO-NEXT:   $x5 = PseudoCALLReg target-flags(riscv-call) @OUTLINED_FUNCTION_0, implicit-def $x5, implicit-def $x10, implicit-def $x11, implicit-def $x12, implicit $x10, implicit $x11
+  ; RV32I-MO-NEXT:   $x11 = ORI $x11, 1023
+  ; RV32I-MO-NEXT:   $x12 = ADDI $x10, 17
+  ; RV32I-MO-NEXT:   $x11 = AND $x12, $x11
+  ; RV32I-MO-NEXT:   $x10 = SUB $x10, $x11
   ; RV32I-MO-NEXT:   BEQ $x10, $x11, %bb.1
   ; RV32I-MO-NEXT: {{  $}}
   ; RV32I-MO-NEXT: bb.1:
@@ -65,7 +68,10 @@ body:             |
   ; RV64I-MO: bb.0:
   ; RV64I-MO-NEXT:   liveins: $x10, $x11
   ; RV64I-MO-NEXT: {{  $}}
-  ; RV64I-MO-NEXT:   $x5 = PseudoCALLReg target-flags(riscv-call) @OUTLINED_FUNCTION_0, implicit-def $x5, implicit-def $x10, implicit-def $x11, implicit-def $x12, implicit $x10, implicit $x11
+  ; RV64I-MO-NEXT:   $x11 = ORI $x11, 1023
+  ; RV64I-MO-NEXT:   $x12 = ADDI $x10, 17
+  ; RV64I-MO-NEXT:   $x11 = AND $x12, $x11
+  ; RV64I-MO-NEXT:   $x10 = SUB $x10, $x11
   ; RV64I-MO-NEXT:   BEQ $x10, $x11, %bb.1
   ; RV64I-MO-NEXT: {{  $}}
   ; RV64I-MO-NEXT: bb.1: