Fix PR2471, which is a bug involving an invalid promotion from a conditional load.

llvm-svn: 52525

llvm/lib/Transforms/Scalar/InstructionCombining.cpp

@@ -10062,10 +10062,16 @@ static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
   while (BBI != E) {
     --BBI;
 
+    // If we see a free or a call (which might do a free) the pointer could be
+    // marked invalid.
+    if (isa<FreeInst>(BBI) || isa<CallInst>(BBI))
+      return false;
+    
     if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
       if (LI->getOperand(0) == V) return true;
-    } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
+    } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
       if (SI->getOperand(1) == V) return true;
+    }
 
   }
   return false;

llvm/test/Transforms/InstCombine/2008-06-19-UncondLoad.ll

@@ -0,0 +1,16 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep load | count 3
+; PR2471
+
+declare i32 @x(i32*)
+define i32 @b(i32* %a, i32* %b) {
+entry:
+        %tmp1 = load i32* %a            
+        %tmp3 = load i32* %b           
+        %add = add i32 %tmp1, %tmp3   
+        %call = call i32 @x( i32* %a )
+        %tobool = icmp ne i32 %add, 0
+	; not safe to turn into an uncond load
+        %cond = select i1 %tobool, i32* %b, i32* %a             
+        %tmp8 = load i32* %cond       
+        ret i32 %tmp8
+}