Update LLVM to r97873.

3 files changed, 153 insertions, 5 deletions

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 1f8053a..8288e96 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -194,11 +194,10 @@ Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
   const Type *ITy = GetCompareTy(LHS);
   
   // icmp X, X -> true/false
-  if (LHS == RHS)
+  // X icmp undef -> true/false.  For example, icmp ugt %X, undef -> false
+  // because X could be 0.
+  if (LHS == RHS || isa<UndefValue>(RHS))
     return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
-
-  if (isa<UndefValue>(RHS))                  // X icmp undef -> undef
-    return UndefValue::get(ITy);
   
   // icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
   // addresses never equal each other!  We already know that Op0 != Op1.
diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index f5f10c8..e27da96 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -15,6 +15,7 @@
 
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/Analysis/LoopInfo.h"
+#include "llvm/IntrinsicInst.h"
 #include "llvm/LLVMContext.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/ADT/STLExtras.h"
@@ -137,6 +138,10 @@ Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode,
   if (IP != BlockBegin) {
     --IP;
     for (; ScanLimit; --IP, --ScanLimit) {
+      // Don't count dbg.value against the ScanLimit, to avoid perturbing the
+      // generated code.
+      if (isa<DbgInfoIntrinsic>(IP))
+        ScanLimit++;
       if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
           IP->getOperand(1) == RHS)
         return IP;
@@ -505,6 +510,10 @@ Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
     if (IP != BlockBegin) {
       --IP;
       for (; ScanLimit; --IP, --ScanLimit) {
+        // Don't count dbg.value against the ScanLimit, to avoid perturbing the
+        // generated code.
+        if (isa<DbgInfoIntrinsic>(IP))
+          ScanLimit++;
         if (IP->getOpcode() == Instruction::GetElementPtr &&
             IP->getOperand(0) == V && IP->getOperand(1) == Idx)
           return IP;
@@ -1258,8 +1267,19 @@ Value *SCEVExpander::expand(const SCEV *S) {
        L = L->getParentLoop())
     if (S->isLoopInvariant(L)) {
       if (!L) break;
-      if (BasicBlock *Preheader = L->getLoopPreheader())
+      if (BasicBlock *Preheader = L->getLoopPreheader()) {
         InsertPt = Preheader->getTerminator();
+        BasicBlock::iterator IP = InsertPt;
+        // Back past any debug info instructions.  Sometimes we inserted
+        // something earlier before debug info but after any real instructions.
+        // This should behave the same as if debug info was not present.
+        while (IP != Preheader->begin()) {
+          --IP;
+          if (!isa<DbgInfoIntrinsic>(IP))
+            break;
+          InsertPt = IP;
+        }
+      }
     } else {
       // If the SCEV is computable at this level, insert it into the header
       // after the PHIs (and after any other instructions that we've inserted
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 09344a3..92cbb7c 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -23,6 +23,7 @@
 #include "llvm/Target/TargetData.h"
 #include "llvm/Support/GetElementPtrTypeIterator.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include <cstring>
 using namespace llvm;
 
@@ -1436,3 +1437,131 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset,
   // The array isn't null terminated, but maybe this is a memcpy, not a strcpy.
   return true;
 }
+
+// These next two are very similar to the above, but also look through PHI
+// nodes.
+// TODO: See if we can integrate these two together.
+
+/// GetStringLengthH - If we can compute the length of the string pointed to by
+/// the specified pointer, return 'len+1'.  If we can't, return 0.
+static uint64_t GetStringLengthH(Value *V, SmallPtrSet<PHINode*, 32> &PHIs) {
+  // Look through noop bitcast instructions.
+  if (BitCastInst *BCI = dyn_cast<BitCastInst>(V))
+    return GetStringLengthH(BCI->getOperand(0), PHIs);
+
+  // If this is a PHI node, there are two cases: either we have already seen it
+  // or we haven't.
+  if (PHINode *PN = dyn_cast<PHINode>(V)) {
+    if (!PHIs.insert(PN))
+      return ~0ULL;  // already in the set.
+
+    // If it was new, see if all the input strings are the same length.
+    uint64_t LenSoFar = ~0ULL;
+    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+      uint64_t Len = GetStringLengthH(PN->getIncomingValue(i), PHIs);
+      if (Len == 0) return 0; // Unknown length -> unknown.
+
+      if (Len == ~0ULL) continue;
+
+      if (Len != LenSoFar && LenSoFar != ~0ULL)
+        return 0;    // Disagree -> unknown.
+      LenSoFar = Len;
+    }
+
+    // Success, all agree.
+    return LenSoFar;
+  }
+
+  // strlen(select(c,x,y)) -> strlen(x) ^ strlen(y)
+  if (SelectInst *SI = dyn_cast<SelectInst>(V)) {
+    uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs);
+    if (Len1 == 0) return 0;
+    uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs);
+    if (Len2 == 0) return 0;
+    if (Len1 == ~0ULL) return Len2;
+    if (Len2 == ~0ULL) return Len1;
+    if (Len1 != Len2) return 0;
+    return Len1;
+  }
+
+  // If the value is not a GEP instruction nor a constant expression with a
+  // GEP instruction, then return unknown.
+  User *GEP = 0;
+  if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
+    GEP = GEPI;
+  } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
+    if (CE->getOpcode() != Instruction::GetElementPtr)
+      return 0;
+    GEP = CE;
+  } else {
+    return 0;
+  }
+
+  // Make sure the GEP has exactly three arguments.
+  if (GEP->getNumOperands() != 3)
+    return 0;
+
+  // Check to make sure that the first operand of the GEP is an integer and
+  // has value 0 so that we are sure we're indexing into the initializer.
+  if (ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
+    if (!Idx->isZero())
+      return 0;
+  } else
+    return 0;
+
+  // If the second index isn't a ConstantInt, then this is a variable index
+  // into the array.  If this occurs, we can't say anything meaningful about
+  // the string.
+  uint64_t StartIdx = 0;
+  if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
+    StartIdx = CI->getZExtValue();
+  else
+    return 0;
+
+  // The GEP instruction, constant or instruction, must reference a global
+  // variable that is a constant and is initialized. The referenced constant
+  // initializer is the array that we'll use for optimization.
+  GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
+  if (!GV || !GV->isConstant() || !GV->hasInitializer() ||
+      GV->mayBeOverridden())
+    return 0;
+  Constant *GlobalInit = GV->getInitializer();
+
+  // Handle the ConstantAggregateZero case, which is a degenerate case. The
+  // initializer is constant zero so the length of the string must be zero.
+  if (isa<ConstantAggregateZero>(GlobalInit))
+    return 1;  // Len = 0 offset by 1.
+
+  // Must be a Constant Array
+  ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
+  if (!Array || !Array->getType()->getElementType()->isIntegerTy(8))
+    return false;
+
+  // Get the number of elements in the array
+  uint64_t NumElts = Array->getType()->getNumElements();
+
+  // Traverse the constant array from StartIdx (derived above) which is
+  // the place the GEP refers to in the array.
+  for (unsigned i = StartIdx; i != NumElts; ++i) {
+    Constant *Elt = Array->getOperand(i);
+    ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
+    if (!CI) // This array isn't suitable, non-int initializer.
+      return 0;
+    if (CI->isZero())
+      return i-StartIdx+1; // We found end of string, success!
+  }
+
+  return 0; // The array isn't null terminated, conservatively return 'unknown'.
+}
+
+/// GetStringLength - If we can compute the length of the string pointed to by
+/// the specified pointer, return 'len+1'.  If we can't, return 0.
+uint64_t llvm::GetStringLength(Value *V) {
+  if (!V->getType()->isPointerTy()) return 0;
+
+  SmallPtrSet<PHINode*, 32> PHIs;
+  uint64_t Len = GetStringLengthH(V, PHIs);
+  // If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return
+  // an empty string as a length.
+  return Len == ~0ULL ? 1 : Len;
+}