From: Ted Kremenek <kremenek@apple.com>
Date: Thu, 20 Jan 2011 21:25:31 +0000 (+0000)
Subject: Relax CFG assertions in UninitializedValuesV2 when
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2d4bed140f65d713673d2d32ec3adadc960078c6;p=clang

Relax CFG assertions in UninitializedValuesV2 when
handling pseudo-path sensitivity, and instead
use those assertion conditions as dynamic checks.
These assertions would be violated when analyzing
a CFG where some branches where optimized away
during CFG construction because their branch
conditions could be trivially determined.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123943 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/UninitializedValuesV2.cpp b/lib/Analysis/UninitializedValuesV2.cpp
index 55769bd2db..121dcf909e 100644
--- a/lib/Analysis/UninitializedValuesV2.cpp
+++ b/lib/Analysis/UninitializedValuesV2.cpp
@@ -156,7 +156,7 @@ static BinaryOperator *getLogicalOperatorInChain(const CFGBlock *block) {
 llvm::BitVector &CFGBlockValues::getBitVector(const CFGBlock *block,
                                               const CFGBlock *dstBlock) {
   unsigned idx = block->getBlockID();
-  if (dstBlock && block->succ_size() == 2) {
+  if (dstBlock && block->succ_size() == 2 && block->pred_size() == 2) {
     assert(block->getTerminator());
     if (getLogicalOperatorInChain(block)) {
       if (*block->succ_begin() == dstBlock)
@@ -460,20 +460,19 @@ static bool runOnBlock(const CFGBlock *block, const CFG &cfg,
                        UninitVariablesHandler *handler = 0) {
   
   if (const BinaryOperator *b = getLogicalOperatorInChain(block)) {
-    assert(block->pred_size() == 2);
-    assert(block->succ_size() == 2);
-    assert(block->getTerminatorCondition() == b);
-    
-    BVPair valsAB = vals.getPredBitVectors(block);
-    vals.mergeIntoScratch(*valsAB.first, true);
-    vals.mergeIntoScratch(*valsAB.second, false);
-    valsAB.second = &vals.getScratch();
-    if (b->getOpcode() == BO_LOr) {
-      // Ensure the invariant that 'first' corresponds to the true
-      // branch and 'second' to the false.
-      std::swap(valsAB.first, valsAB.second);
+    if (block->pred_size() == 2 && block->succ_size() == 2) {
+      assert(block->getTerminatorCondition() == b);    
+      BVPair valsAB = vals.getPredBitVectors(block);
+      vals.mergeIntoScratch(*valsAB.first, true);
+      vals.mergeIntoScratch(*valsAB.second, false);
+      valsAB.second = &vals.getScratch();
+      if (b->getOpcode() == BO_LOr) {
+        // Ensure the invariant that 'first' corresponds to the true
+        // branch and 'second' to the false.
+        std::swap(valsAB.first, valsAB.second);
+      }
+      return vals.updateBitVectors(block, valsAB);
     }
-    return vals.updateBitVectors(block, valsAB);
   }
 
   // Default behavior: merge in values of predecessor blocks.    
diff --git a/test/SemaCXX/uninit-variables.cpp b/test/SemaCXX/uninit-variables.cpp
index e971357ca7..0d6920ceb3 100644
--- a/test/SemaCXX/uninit-variables.cpp
+++ b/test/SemaCXX/uninit-variables.cpp
@@ -13,3 +13,31 @@ int test2_aux() {
   return x; // no-warning
 }
 
+// Handle cases where the CFG may constant fold some branches, thus
+// mitigating the need for some path-sensitivity in the analysis.
+unsigned test3_aux();
+unsigned test3() {
+  unsigned x = 0;
+  const bool flag = true;
+  if (flag && (x = test3_aux()) == 0) {
+    return x;
+  }
+  return x;
+}
+unsigned test3_b() {
+  unsigned x ;
+  const bool flag = true;
+  if (flag && (x = test3_aux()) == 0) {
+    x = 1;
+  }
+  return x; // no-warning
+}
+unsigned test3_c() {
+  unsigned x ;
+  const bool flag = false;
+  if (flag && (x = test3_aux()) == 0) {
+    x = 1;
+  }
+  return x; // expected-warning{{use of uninitialized variable 'x'}}
+}
+