[SystemZ] Recognize INLINEASM_BR in backend

Handle the remaining cases also by handling asm goto in
SystemZInstrInfo::getBranchInfo().

Review: Ulrich Weigand
https://reviews.llvm.org/D67151

llvm-svn: 371048

llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp

@@ -462,13 +462,13 @@ bool SystemZInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
       break;
 
     // A terminator that isn't a branch can't easily be handled by this
-    // analysis.  Asm goto is not understood / optimized.
-    if (!I->isBranch() || I->getOpcode() == SystemZ::INLINEASM_BR)
+    // analysis.
+    if (!I->isBranch())
       return true;
 
     // Can't handle indirect branches.
     SystemZII::Branch Branch(getBranchInfo(*I));
-    if (!Branch.Target->isMBB())
+    if (!Branch.hasMBBTarget())
       return true;
 
     // Punt on compound branches.
@@ -478,7 +478,7 @@ bool SystemZInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
     if (Branch.CCMask == SystemZ::CCMASK_ANY) {
       // Handle unconditional branches.
       if (!AllowModify) {
-        TBB = Branch.Target->getMBB();
+        TBB = Branch.getMBBTarget();
         continue;
       }
 
@@ -490,7 +490,7 @@ bool SystemZInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
       FBB = nullptr;
 
       // Delete the JMP if it's equivalent to a fall-through.
-      if (MBB.isLayoutSuccessor(Branch.Target->getMBB())) {
+      if (MBB.isLayoutSuccessor(Branch.getMBBTarget())) {
         TBB = nullptr;
         I->eraseFromParent();
         I = MBB.end();
@@ -498,7 +498,7 @@ bool SystemZInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
       }
 
       // TBB is used to indicate the unconditinal destination.
-      TBB = Branch.Target->getMBB();
+      TBB = Branch.getMBBTarget();
       continue;
     }
 
@@ -506,7 +506,7 @@ bool SystemZInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
     if (Cond.empty()) {
       // FIXME: add X86-style branch swap
       FBB = TBB;
-      TBB = Branch.Target->getMBB();
+      TBB = Branch.getMBBTarget();
       Cond.push_back(MachineOperand::CreateImm(Branch.CCValid));
       Cond.push_back(MachineOperand::CreateImm(Branch.CCMask));
       continue;
@@ -517,7 +517,7 @@ bool SystemZInstrInfo::analyzeBranch(MachineBasicBlock &MBB,
 
     // Only handle the case where all conditional branches branch to the same
     // destination.
-    if (TBB != Branch.Target->getMBB())
+    if (TBB != Branch.getMBBTarget())
       return true;
 
     // If the conditions are the same, we can leave them alone.
@@ -547,7 +547,7 @@ unsigned SystemZInstrInfo::removeBranch(MachineBasicBlock &MBB,
       continue;
     if (!I->isBranch())
       break;
-    if (!getBranchInfo(*I).Target->isMBB())
+    if (!getBranchInfo(*I).hasMBBTarget())
       break;
     // Remove the branch.
     I->eraseFromParent();
@@ -1546,6 +1546,10 @@ SystemZInstrInfo::getBranchInfo(const MachineInstr &MI) const {
     return SystemZII::Branch(SystemZII::BranchCLG, SystemZ::CCMASK_ICMP,
                              MI.getOperand(2).getImm(), &MI.getOperand(3));
 
+  case SystemZ::INLINEASM_BR:
+    // Don't try to analyze asm goto, so pass nullptr as branch target argument.
+    return SystemZII::Branch(SystemZII::AsmGoto, 0, 0, nullptr);
+
   default:
     llvm_unreachable("Unrecognized branch opcode");
   }

llvm/lib/Target/SystemZ/SystemZInstrInfo.h

@@ -100,11 +100,18 @@ enum BranchType {
 
   // An instruction that decrements a 64-bit register and branches if
   // the result is nonzero.
-  BranchCTG
+  BranchCTG,
+
+  // An instruction representing an asm goto statement.
+  AsmGoto
 };
 
 // Information about a branch instruction.
-struct Branch {
+class Branch {
+  // The target of the branch. In case of INLINEASM_BR, this is nullptr.
+  const MachineOperand *Target;
+
+public:
   // The type of the branch.
   BranchType Type;
 
@@ -114,12 +121,15 @@ struct Branch {
   // CCMASK_<N> is set if the branch should be taken when CC == N.
   unsigned CCMask;
 
-  // The target of the branch.
-  const MachineOperand *Target;
-
   Branch(BranchType type, unsigned ccValid, unsigned ccMask,
          const MachineOperand *target)
-    : Type(type), CCValid(ccValid), CCMask(ccMask), Target(target) {}
+    : Target(target), Type(type), CCValid(ccValid), CCMask(ccMask) {}
+
+  bool isIndirect() { return Target != nullptr && Target->isReg(); }
+  bool hasMBBTarget() { return Target != nullptr && Target->isMBB(); }
+  MachineBasicBlock *getMBBTarget() {
+    return hasMBBTarget() ? Target->getMBB() : nullptr;
+  }
 };
 
 // Kinds of fused compares in compare-and-* instructions.  Together with type

llvm/lib/Target/SystemZ/SystemZLongBranch.cpp

@@ -258,7 +258,7 @@ TerminatorInfo SystemZLongBranch::describeTerminator(MachineInstr &MI) {
     }
     Terminator.Branch = &MI;
     Terminator.TargetBlock =
-      TII->getBranchInfo(MI).Target->getMBB()->getNumber();
+      TII->getBranchInfo(MI).getMBBTarget()->getNumber();
   }
   return Terminator;
 }

llvm/lib/Target/SystemZ/SystemZMachineScheduler.cpp

@@ -108,8 +108,8 @@ void SystemZPostRASchedStrategy::enterMBB(MachineBasicBlock *NextMBB) {
        I != SinglePredMBB->end(); I++) {
     LLVM_DEBUG(dbgs() << "** Emitting incoming branch: "; I->dump(););
     bool TakenBranch = (I->isBranch() &&
-      (TII->getBranchInfo(*I).Target->isReg() || // Relative branch
-       TII->getBranchInfo(*I).Target->getMBB() == MBB));
+                        (TII->getBranchInfo(*I).isIndirect() ||
+                         TII->getBranchInfo(*I).getMBBTarget() == MBB));
     HazardRec->emitInstruction(&*I, TakenBranch);
     if (TakenBranch)
       break;

llvm/test/CodeGen/SystemZ/asm-20.ll

@@ -1,10 +1,10 @@
 ; Test that asm goto can be compiled.
 ;
-; RUN: llc < %s -mtriple=s390x-linux-gnu
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14
 
 define i32 @c() {
 entry:
-  callbr void asm sideeffect "", "X"(i8* blockaddress(@c, %d))
+  callbr void asm sideeffect "j d", "X"(i8* blockaddress(@c, %d))
           to label %asm.fallthrough [label %d]
 
 asm.fallthrough:               ; preds = %entry