[llvm] r199061 - Handle bundled terminators in isBlockOnlyReachableByFallthrough.

[Jakob Stoklund Olesen]

Author: stoklund
Date: Sun Jan 12 13:24:08 2014
New Revision: 199061

URL: http://llvm.org/viewvc/llvm-project?rev=199061&view=rev
Log:
Handle bundled terminators in isBlockOnlyReachableByFallthrough.

Targets like SPARC and MIPS have delay slots and normally bundle the
delay slot instruction with the corresponding terminator.

Teach isBlockOnlyReachableByFallthrough to find any MBB operands on
bundled terminators so SPARC doesn't need to specialize this function.

Added:
    llvm/trunk/test/CodeGen/SPARC/missinglabel.ll
Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
    llvm/trunk/lib/Target/Sparc/SparcAsmPrinter.cpp

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp?rev=199061&r1=199060&r2=199061&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp Sun Jan 12 13:24:08 2014
@@ -22,6 +22,7 @@
 #include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBundle.h"
 #include "llvm/CodeGen/MachineJumpTableInfo.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
@@ -2216,14 +2217,13 @@ isBlockOnlyReachableByFallthrough(const
     if (!MI.isBranch() || MI.isIndirectBranch())
       return false;
 
-    // If we are the operands of one of the branches, this is not
-    // a fall through.
-    for (MachineInstr::mop_iterator OI = MI.operands_begin(),
-           OE = MI.operands_end(); OI != OE; ++OI) {
-      const MachineOperand& OP = *OI;
-      if (OP.isJTI())
+    // If we are the operands of one of the branches, this is not a fall
+    // through. Note that targets with delay slots will usually bundle
+    // terminators with the delay slot instruction.
+    for (ConstMIBundleOperands OP(&MI); OP.isValid(); ++OP) {
+      if (OP->isJTI())
         return false;
-      if (OP.isMBB() && OP.getMBB() == MBB)
+      if (OP->isMBB() && OP->getMBB() == MBB)
         return false;
     }
   }

Modified: llvm/trunk/lib/Target/Sparc/SparcAsmPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Sparc/SparcAsmPrinter.cpp?rev=199061&r1=199060&r2=199061&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Sparc/SparcAsmPrinter.cpp (original)
+++ llvm/trunk/lib/Target/Sparc/SparcAsmPrinter.cpp Sun Jan 12 13:24:08 2014
@@ -65,10 +65,6 @@ namespace {
     bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                                unsigned AsmVariant, const char *ExtraCode,
                                raw_ostream &O);
-
-    virtual bool isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB)
-                       const;
-
   };
 } // end of anonymous namespace
 
@@ -391,37 +387,6 @@ bool SparcAsmPrinter::PrintAsmMemoryOper
   return false;
 }
 
-/// isBlockOnlyReachableByFallthough - Return true if the basic block has
-/// exactly one predecessor and the control transfer mechanism between
-/// the predecessor and this block is a fall-through.
-///
-/// This overrides AsmPrinter's implementation to handle delay slots.
-bool SparcAsmPrinter::
-isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const {
-  // If this is a landing pad, it isn't a fall through.  If it has no preds,
-  // then nothing falls through to it.
-  if (MBB->isLandingPad() || MBB->pred_empty())
-    return false;
-
-  // If there isn't exactly one predecessor, it can't be a fall through.
-  MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PI2 = PI;
-  ++PI2;
-  if (PI2 != MBB->pred_end())
-    return false;
-
-  // The predecessor has to be immediately before this block.
-  const MachineBasicBlock *Pred = *PI;
-
-  if (!Pred->isLayoutSuccessor(MBB))
-    return false;
-
-  // Check if the last terminator is an unconditional branch.
-  MachineBasicBlock::const_iterator I = Pred->end();
-  while (I != Pred->begin() && !(--I)->isTerminator())
-    ; // Noop
-  return I == Pred->end() || !I->isBarrier();
-}
-
 // Force static initialization.
 extern "C" void LLVMInitializeSparcAsmPrinter() {
   RegisterAsmPrinter<SparcAsmPrinter> X(TheSparcTarget);

Added: llvm/trunk/test/CodeGen/SPARC/missinglabel.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/SPARC/missinglabel.ll?rev=199061&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/SPARC/missinglabel.ll (added)
+++ llvm/trunk/test/CodeGen/SPARC/missinglabel.ll Sun Jan 12 13:24:08 2014
@@ -0,0 +1,23 @@
+; RUN: llc < %s -verify-machineinstrs | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64-S128"
+target triple = "sparc64-unknown-linux-gnu"
+
+define void @f() align 2 {
+entry:
+; CHECK: %xcc, .LBB0_1
+  %cmp = icmp eq i64 undef, 0
+  br i1 %cmp, label %targetblock, label %cond.false
+
+cond.false:
+  unreachable
+
+; CHECK: .LBB0_1: ! %targetblock
+targetblock:
+  br i1 undef, label %cond.false.i83, label %exit.i85
+
+cond.false.i83:
+  unreachable
+
+exit.i85:
+  unreachable
+}