Revert r135217, which wasn't the correct fix for PR10358. With this

patch, we actually move the state-machine for the value set backwards
one step. This can pretty easily lead to infinite loops where we
continually try to propagate a bit, succeed for one iteration, but then
back up because we find an uninitialized use.

A reduced test case from PR10379 is included.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135359 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/UninitializedValues.cpp

@@ -495,10 +495,8 @@ void TransferFunctions::VisitBinaryOperator(clang::BinaryOperator *bo) {
 
       ValueVector::reference val = vals[vd];
       if (isUninitialized(val)) {
-        if (bo->getOpcode() != BO_Assign) {
+        if (bo->getOpcode() != BO_Assign)
           reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
-          val = Unknown;
-        } else
         val = Initialized;
       }
       return;
@@ -528,7 +526,7 @@ void TransferFunctions::VisitUnaryOperator(clang::UnaryOperator *uo) {
         if (isUninitialized(val)) {
           reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
           // Don't cascade warnings.
-          val = Unknown;
+          val = Initialized;
         }
         return;
       }
@@ -560,7 +558,7 @@ void TransferFunctions::VisitCastExpr(clang::CastExpr *ce) {
         if (isUninitialized(val)) {
           reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
           // Don't cascade warnings.
-          vals[vd] = Unknown;
+          vals[vd] = Initialized;
         }
       }
       return;

test/Sema/uninit-variables.c

@@ -77,7 +77,7 @@ int test11(unsigned n) {
 }
 
 void test12(unsigned n) {
-  for (unsigned i ; n ; ++i) ; // expected-warning{{variable 'i' is uninitialized when used here}} expected-note{{variable 'i' is declared here}} expected-note{{add initialization to silence this warning}}
+  for (unsigned i ; n ; ++i) ; // expected-warning{{variable 'i' may be uninitialized when used here}} expected-note{{variable 'i' is declared here}} expected-note{{add initialization to silence this warning}}
 }
 
 int test13() {
@@ -237,7 +237,7 @@ void test36()
   void **pc; // expected-note{{variable 'pc' is declared here}} expected-note{{add initialization to silence this warning}}
   void *dummy[] = { &&L1, &&L2 };
  L1:
-    goto *pc; // expected-warning{{variable 'pc' is uninitialized when used here}}
+    goto *pc; // expected-warning{{variable 'pc' may be uninitialized when used here}}
  L2:
     goto *pc;
 }
@@ -289,7 +289,7 @@ void test43_aux(int x);
 void test43(int i) {
   int x; // expected-note {{variable 'x' is declared here}} expected-note{{add initialization to silence this warning}}
   for (i = 0 ; i < 10; i++)
-    test43_aux(x++); // expected-warning {{variable 'x' is uninitialized when used here}}
+    test43_aux(x++); // expected-warning {{variable 'x' may be uninitialized when used here}}
 }
 
 void test44(int i) {
@@ -297,7 +297,7 @@ void test44(int i) {
   int y; // expected-note {{variable 'y' is declared here}} expected-note{{add initialization to silence this warning}}
   for (i = 0; i < 10; i++ ) {
     test43_aux(x++); // no-warning
-    x += y; // expected-warning {{variable 'y' is uninitialized when used here}}
+    x += y; // expected-warning {{variable 'y' may be uninitialized when used here}}
   }
 }
 
@@ -352,3 +352,18 @@ int test52(int a, int b) {
   }
   return x; // expected-warning {{variable 'x' may be uninitialized when used here}}
 }
+
+// This CFG caused the uninitialized values warning to inf-loop.
+extern int PR10379_g();
+void PR10379_f(int *len) {
+  int new_len; // expected-note {{variable 'new_len' is declared here}} expected-note{{add initialization to silence this warning}}
+  for (int i = 0; i < 42 && PR10379_g() == 0; i++) {
+    if (PR10379_g() == 1)
+      continue;
+    if (PR10379_g() == 2)
+      PR10379_f(&new_len);
+    else if (PR10379_g() == 3)
+      PR10379_f(&new_len);
+    *len += new_len; // expected-warning {{variable 'new_len' may be uninitialized when used here}}
+  }
+}