[GV] Remove dead code which is really difficult to decipher.

Actually it took me couple of hours trying to make sense of them and
only to find they are dead code.  I guess the original author used
"allSingleSucc" to indicate if there are any critial edge emanating
from some blocks, and tried to perform code motion (actually speculation)
in the presence of these critical edges; but later on he/she changed mind
and decided to perform edge-splitting first.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180951 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/GVN.cpp

@@ -1526,7 +1526,6 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
   BasicBlock *LoadBB = LI->getParent();
   BasicBlock *TmpBB = LoadBB;
 
-  bool allSingleSucc = true;
   while (TmpBB->getSinglePredecessor()) {
     TmpBB = TmpBB->getSinglePredecessor();
     if (TmpBB == LoadBB) // Infinite (unreachable) loop.
@@ -1615,13 +1614,8 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
     // pointer if it is not available.
     PHITransAddr Address(LI->getPointerOperand(), TD);
     Value *LoadPtr = 0;
-    if (allSingleSucc) {
-      LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred,
-                                                  *DT, NewInsts);
-    } else {
-      Address.PHITranslateValue(LoadBB, UnavailablePred, DT);
-      LoadPtr = Address.getAddr();
-    }
+    LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred,
+                                                *DT, NewInsts);
 
     // If we couldn't find or insert a computation of this phi translated value,
     // we fail PRE.
@@ -1632,24 +1626,6 @@ bool GVN::processNonLocalLoad(LoadInst *LI) {
       break;
     }
 
-    // Make sure it is valid to move this load here.  We have to watch out for:
-    //  @1 = getelementptr (i8* p, ...
-    //  test p and branch if == 0
-    //  load @1
-    // It is valid to have the getelementptr before the test, even if p can
-    // be 0, as getelementptr only does address arithmetic.
-    // If we are not pushing the value through any multiple-successor blocks
-    // we do not have this case.  Otherwise, check that the load is safe to
-    // put anywhere; this can be improved, but should be conservatively safe.
-    if (!allSingleSucc &&
-        // FIXME: REEVALUTE THIS.
-        !isSafeToLoadUnconditionally(LoadPtr,
-                                     UnavailablePred->getTerminator(),
-                                     LI->getAlignment(), TD)) {
-      CanDoPRE = false;
-      break;
-    }
-
     I->second = LoadPtr;
   }