make sure to set Changed=true when instcombine hacks on the code,

not doing so prevents it from properly iterating and prevents it
from deleting the entire body of dce-iterate.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63476 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 33 insertions, 5 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 7f7592840a..6c571511e7 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -12356,6 +12356,7 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
           if (!I->use_empty())
             I->replaceAllUsesWith(UndefValue::get(I->getType()));
           I->eraseFromParent();
+          Changed = true;
         }
       }
   }
@@ -12375,6 +12376,7 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
 
       I->eraseFromParent();
       RemoveFromWorkList(I);
+      Changed = true;
       continue;
     }
 
@@ -12389,17 +12391,19 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
       ++NumConstProp;
       I->eraseFromParent();
       RemoveFromWorkList(I);
+      Changed = true;
       continue;
     }
 
     if (TD && I->getType()->getTypeID() == Type::VoidTyID) {
       // See if we can constant fold its operands.
-      for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
-        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(i)) {
+      for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
+        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(i))
           if (Constant *NewC = ConstantFoldConstantExpression(CE, TD))
-            i->set(NewC);
-        }
-      }
+            if (NewC != CE) {
+              i->set(NewC);
+              Changed = true;
+            }
     }
 
     // See if we can trivially sink this instruction to a successor basic block.
diff --git a/test/Transforms/InstCombine/dce-iterate.ll b/test/Transforms/InstCombine/dce-iterate.ll
new file mode 100644
index 0000000000..e222970df6
--- /dev/null
+++ b/test/Transforms/InstCombine/dce-iterate.ll
@@ -0,0 +1,24 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret double .sy}
+
+define internal double @ScaleObjectAdd(double %sx, double %sy, double %sz) nounwind {
+entry:
+        %sx34 = bitcast double %sx to i64               ; <i64> [#uses=1]
+        %sx3435 = zext i64 %sx34 to i960                ; <i960> [#uses=1]
+        %sy22 = bitcast double %sy to i64               ; <i64> [#uses=1]
+        %sy2223 = zext i64 %sy22 to i960                ; <i960> [#uses=1]
+        %sy222324 = shl i960 %sy2223, 320               ; <i960> [#uses=1]
+        %sy222324.ins = or i960 %sx3435, %sy222324              ; <i960> [#uses=1]
+        %sz10 = bitcast double %sz to i64               ; <i64> [#uses=1]
+        %sz1011 = zext i64 %sz10 to i960                ; <i960> [#uses=1]
+        %sz101112 = shl i960 %sz1011, 640               ; <i960> [#uses=1]
+        %sz101112.ins = or i960 %sy222324.ins, %sz101112 
+        
+        %a = trunc i960 %sz101112.ins to i64            ; <i64> [#uses=1]
+        %b = bitcast i64 %a to double           ; <double> [#uses=1]
+        %c = lshr i960 %sz101112.ins, 320               ; <i960> [#uses=1]
+        %d = trunc i960 %c to i64               ; <i64> [#uses=1]
+        %e = bitcast i64 %d to double           ; <double> [#uses=1]
+        %f = add double %b, %e
+
+        ret double %e
+}