[llvm-commits] [llvm] r101420 - /llvm/trunk/lib/CodeGen/MachineSink.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Thu Apr 15 18:41:02 2010
New Revision: 101420

URL: http://llvm.org/viewvc/llvm-project?rev=101420&view=rev
Log:
Avoid sinking machine instructions into a loop.

MachineLoopInfo is already available when MachineSinking runs, so the check is
free.

There is no test case because it would require a critical edge into a loop, and
CodeGenPrepare splits those. This check is just to be extra careful.

Modified:
    llvm/trunk/lib/CodeGen/MachineSink.cpp

Modified: llvm/trunk/lib/CodeGen/MachineSink.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineSink.cpp?rev=101420&r1=101419&r2=101420&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineSink.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineSink.cpp Thu Apr 15 18:41:02 2010
@@ -20,6 +20,7 @@
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetInstrInfo.h"
@@ -37,6 +38,7 @@
     const TargetRegisterInfo *TRI;
     MachineRegisterInfo  *RegInfo; // Machine register information
     MachineDominatorTree *DT;   // Machine dominator tree
+    MachineLoopInfo *LI;
     AliasAnalysis *AA;
     BitVector AllocatableSet;   // Which physregs are allocatable?
 
@@ -51,7 +53,9 @@
       MachineFunctionPass::getAnalysisUsage(AU);
       AU.addRequired<AliasAnalysis>();
       AU.addRequired<MachineDominatorTree>();
+      AU.addRequired<MachineLoopInfo>();
       AU.addPreserved<MachineDominatorTree>();
+      AU.addPreserved<MachineLoopInfo>();
     }
   private:
     bool ProcessBlock(MachineBasicBlock &MBB);
@@ -102,6 +106,7 @@
   TRI = TM.getRegisterInfo();
   RegInfo = &MF.getRegInfo();
   DT = &getAnalysis<MachineDominatorTree>();
+  LI = &getAnalysis<MachineLoopInfo>();
   AA = &getAnalysis<AliasAnalysis>();
   AllocatableSet = TRI->getAllocatableSet(MF);
 
@@ -291,6 +296,12 @@
       return false;
     }
 
+    // Don't sink instructions into a loop.
+    if (LI->isLoopHeader(SuccToSinkTo)) {
+      DEBUG(dbgs() << " *** PUNTING: Loop header found\n");
+      return false;
+    }
+
     // Otherwise we are OK with sinking along a critical edge.
     DEBUG(dbgs() << "Sinking along critical edge.\n");
   }