Fix PR7647, handling the case when 'To' ends up being

mutated by recursive simplification.  This also enhances
ReplaceAndSimplifyAllUses to actually do a real RAUW
at the end of it, which updates any value handles
pointing to "From" to start pointing to "To".  This
seems useful for debug info and random other VH users.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108415 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 81 insertions, 14 deletions

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index dbefc2dedb..24cd3433a2 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -440,27 +440,47 @@ void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
                                      const TargetData *TD) {
   assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
   
-  // FromHandle - This keeps a weakvh on the from value so that we can know if
-  // it gets deleted out from under us in a recursive simplification.
+  // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
+  // we can know if it gets deleted out from under us or replaced in a
+  // recursive simplification.
   WeakVH FromHandle(From);
+  WeakVH ToHandle(To);
   
   while (!From->use_empty()) {
     // Update the instruction to use the new value.
-    Use &U = From->use_begin().getUse();
-    Instruction *User = cast<Instruction>(U.getUser());
-    U = To;
+    Use &TheUse = From->use_begin().getUse();
+    Instruction *User = cast<Instruction>(TheUse.getUser());
+    TheUse = To;
+
+    // Check to see if the instruction can be folded due to the operand
+    // replacement.  For example changing (or X, Y) into (or X, -1) can replace
+    // the 'or' with -1.
+    Value *SimplifiedVal;
+    {
+      // Sanity check to make sure 'User' doesn't dangle across
+      // SimplifyInstruction.
+      AssertingVH<> UserHandle(User);
     
-    // See if we can simplify it.
-    if (Value *V = SimplifyInstruction(User, TD)) {
-      // Recursively simplify this.
-      ReplaceAndSimplifyAllUses(User, V, TD);
-      
-      // If the recursive simplification ended up revisiting and deleting 'From'
-      // then we're done.
-      if (FromHandle == 0)
-        return;
+      SimplifiedVal = SimplifyInstruction(User, TD);
+      if (SimplifiedVal == 0) continue;
     }
+    
+    // Recursively simplify this user to the new value.
+    ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD);
+    From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
+    To = ToHandle;
+      
+    assert(ToHandle && "To value deleted by recursive simplification?");
+      
+    // If the recursive simplification ended up revisiting and deleting
+    // 'From' then we're done.
+    if (From == 0)
+      return;
   }
+  
+  // If 'From' has value handles referring to it, do a real RAUW to update them.
+  From->replaceAllUsesWith(To);
+  
   From->eraseFromParent();
 }
 
diff --git a/test/Transforms/JumpThreading/crash.ll b/test/Transforms/JumpThreading/crash.ll
index 480b4a04ee..f0fc61e737 100644
--- a/test/Transforms/JumpThreading/crash.ll
+++ b/test/Transforms/JumpThreading/crash.ll
@@ -387,3 +387,50 @@ if.end:                                           ; preds = %land.end69
   ret void
 }
 
+; PR7647
+define void @test15() nounwind {
+entry:
+  ret void
+  
+if.then237:
+  br label %lbl_664
+
+lbl_596:                                          ; preds = %lbl_664, %for.end37
+  volatile store i64 undef, i64* undef, align 4
+  br label %for.cond111
+
+for.cond111:                                      ; preds = %safe_sub_func_int64_t_s_s.exit, %lbl_596
+  %storemerge = phi i8 [ undef, %cond.true.i100 ], [ 22, %lbl_596 ] ; <i8> [#uses=1]
+  %l_678.5 = phi i64 [ %l_678.3, %cond.true.i100 ], [ undef, %lbl_596 ] ; <i64> [#uses=2]
+  %cmp114 = icmp slt i8 %storemerge, -2           ; <i1> [#uses=1]
+  br i1 %cmp114, label %lbl_664, label %if.end949
+
+lbl_664:                                          ; preds = %for.end1058, %if.then237, %for.cond111
+  %l_678.3 = phi i64 [ %l_678.5, %for.cond111 ], [ %l_678.2, %for.cond1035 ], [ 5, %if.then237 ] ; <i64> [#uses=1]
+  %tobool118 = icmp eq i32 undef, 0               ; <i1> [#uses=1]
+  br i1 %tobool118, label %cond.true.i100, label %lbl_596
+
+cond.true.i100:                                   ; preds = %for.inc120
+  br label %for.cond111
+
+lbl_709:
+  br label %if.end949
+  
+for.cond603:                                      ; preds = %for.body607, %if.end336
+  br i1 undef, label %for.cond603, label %if.end949
+
+if.end949:                                        ; preds = %for.cond603, %lbl_709, %for.cond111
+  %l_678.2 = phi i64 [ %l_678.5, %for.cond111 ], [ undef, %lbl_709 ], [ 5, %for.cond603 ] ; <i64> [#uses=1]
+  br label %for.body1016
+
+for.body1016:                                     ; preds = %for.cond1012
+  br label %for.body1016
+
+for.cond1035:                                     ; preds = %for.inc1055, %if.then1026
+  br i1 undef, label %for.cond1040, label %lbl_664
+
+for.cond1040:                                     ; preds = %for.body1044, %for.cond1035
+  ret void
+}
+
+