have dag combine zap "store undef", which can be formed during call lowering

with undef arguments.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129185 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 23 insertions, 2 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a9afec8..6ad85fa 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6264,6 +6264,10 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
                           Ptr, ST->getPointerInfo(), ST->isVolatile(),
                           ST->isNonTemporal(), OrigAlign);
   }
+  
+  // Turn 'store undef, Ptr' -> nothing.
+  if (Value.getOpcode() == ISD::UNDEF && ST->isUnindexed())
+    return Chain;
 
   // Turn 'store float 1.0, Ptr' -> 'store int 0x12345678, Ptr'
   if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(Value)) {
@@ -6298,8 +6302,10 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
           return DAG.getStore(Chain, N->getDebugLoc(), Tmp,
                               Ptr, ST->getPointerInfo(), ST->isVolatile(),
                               ST->isNonTemporal(), ST->getAlignment());
-        } else if (!ST->isVolatile() &&
-                   TLI.isOperationLegalOrCustom(ISD::STORE, MVT::i32)) {
+        }
+          
+        if (!ST->isVolatile() &&
+            TLI.isOperationLegalOrCustom(ISD::STORE, MVT::i32)) {
           // Many FP stores are not made apparent until after legalize, e.g. for
           // argument passing.  Since this is so common, custom legalize the
           // 64-bit integer store into two 32-bit stores.
diff --git a/test/CodeGen/X86/call-push.ll b/test/CodeGen/X86/call-push.ll
index 02cbccc..7eac522 100644
--- a/test/CodeGen/X86/call-push.ll
+++ b/test/CodeGen/X86/call-push.ll
@@ -27,3 +27,18 @@ UnifiedReturnBlock:             ; preds = %entry
 }
 
 declare i32 @f(%struct.decode_t*)
+
+
+; There should be no store for the undef operand.
+
+; CHECK: _test2:
+; CHECK-NOT: 8(%esp)
+; CHECK: 4(%esp)
+; CHECK: calll 
+declare i32 @foo(i32, i32, i32)
+
+define void @test2() nounwind {
+entry:
+  %call = call i32 @foo(i32 8, i32 6, i32 undef)
+  ret void
+}