From e6992f728a94654e43269580a10a667f18dadba9 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Thu, 10 Sep 2009 23:37:55 +0000
Subject: Factor out the code for checking that all indices in a getelementptr
 are within the notional bounds of the static type of the getelementptr (which
 is not the same as "inbounds") from GlobalOpt into a utility routine, and use
 it in ConstantFold.cpp to check whether there are any mis-behaved indices.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81478 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/GlobalOpt.cpp | 19 ++++---------------
 lib/VMCore/ConstantFold.cpp      |  8 ++++++++
 lib/VMCore/Constants.cpp         | 26 ++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 15 deletions(-)

(limited to 'lib')

diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index b995a3d..63bc03d 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2045,25 +2045,14 @@ static bool isSimpleEnoughPointerToCommit(Constant *C, LLVMContext &Context) {
       if (!GV->hasDefinitiveInitializer())
         return false;
 
-      gep_type_iterator GEPI = gep_type_begin(CE), E = gep_type_end(CE);
-      User::op_iterator OI = next(CE->op_begin());
-
       // The first index must be zero.
-      ConstantInt *CI = dyn_cast<ConstantInt>(*OI);
+      ConstantInt *CI = dyn_cast<ConstantInt>(*next(CE->op_begin()));
       if (!CI || !CI->isZero()) return false;
-      ++GEPI;
-      ++OI;
 
       // The remaining indices must be compile-time known integers within the
-      // bounds of the corresponding static array types.
-      for (; GEPI != E; ++GEPI, ++OI) {
-        CI = dyn_cast<ConstantInt>(*OI);
-        if (!CI) return false;
-        if (const ArrayType *ATy = dyn_cast<ArrayType>(*GEPI))
-          if (CI->getValue().getActiveBits() > 64 ||
-              CI->getZExtValue() >= ATy->getNumElements())
-            return false;
-      }
+      // notional bounds of the corresponding static array types.
+      if (!CE->isGEPWithNoNotionalOverIndexing())
+        return false;
 
       return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE,
                                                     Context);
diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 701a195..da6c8d4 100644
--- a/lib/VMCore/ConstantFold.cpp
+++ b/lib/VMCore/ConstantFold.cpp
@@ -1329,6 +1329,14 @@ static ICmpInst::Predicate evaluateICmpRelation(LLVMContext &Context,
             // ordering of the resultant pointers.
             unsigned i = 1;
 
+            // The logic below assumes that the result of the comparison
+            // can be determined by finding the first index that differs.
+            // This doesn't work if there is over-indexing in any
+            // subsequent indices, so check for that case first.
+            if (!CE1->isGEPWithNoNotionalOverIndexing() ||
+                !CE2->isGEPWithNoNotionalOverIndexing())
+               return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
+
             // Compare all of the operands the GEP's have in common.
             gep_type_iterator GTI = gep_type_begin(CE1);
             for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
diff --git a/lib/VMCore/Constants.cpp b/lib/VMCore/Constants.cpp
index a5b4f28..54445cd 100644
--- a/lib/VMCore/Constants.cpp
+++ b/lib/VMCore/Constants.cpp
@@ -28,6 +28,7 @@
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/GetElementPtrTypeIterator.h"
 #include "llvm/System/Mutex.h"
 #include "llvm/System/RWMutex.h"
 #include "llvm/System/Threading.h"
@@ -652,6 +653,31 @@ bool ConstantExpr::isCompare() const {
   return getOpcode() == Instruction::ICmp || getOpcode() == Instruction::FCmp;
 }
 
+bool ConstantExpr::isGEPWithNoNotionalOverIndexing() const {
+  if (getOpcode() != Instruction::GetElementPtr) return false;
+
+  gep_type_iterator GEPI = gep_type_begin(this), E = gep_type_end(this);
+  User::const_op_iterator OI = next(this->op_begin());
+
+  // Skip the first index, as it has no static limit.
+  ++GEPI;
+  ++OI;
+
+  // The remaining indices must be compile-time known integers within the
+  // bounds of the corresponding notional static array types.
+  for (; GEPI != E; ++GEPI, ++OI) {
+    ConstantInt *CI = dyn_cast<ConstantInt>(*OI);
+    if (!CI) return false;
+    if (const ArrayType *ATy = dyn_cast<ArrayType>(*GEPI))
+      if (CI->getValue().getActiveBits() > 64 ||
+          CI->getZExtValue() >= ATy->getNumElements())
+        return false;
+  }
+
+  // All the indices checked out.
+  return true;
+}
+
 bool ConstantExpr::hasIndices() const {
   return getOpcode() == Instruction::ExtractValue ||
          getOpcode() == Instruction::InsertValue;
-- 
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