Reapply 239795 - [InstCombine] Propagate non-null facts to call parameters

The original change broke clang side tests.  I will be submitting those momentarily.  This change includes post commit feedback on the original change from from Pete Cooper.

Original Submission comments:
If a parameter to a function is known non-null, use the existing parameter attributes to record that fact at the call site. This has no optimization benefit by itself - that I know of - but is an enabling change for http://reviews.llvm.org/D9129.

Differential Revision: http://reviews.llvm.org/D9132

llvm-svn: 239849

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index e83b9dd36ae..6de380bcad6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1391,11 +1391,29 @@ static IntrinsicInst *FindInitTrampoline(Value *Callee) {
 // visitCallSite - Improvements for call and invoke instructions.
 //
 Instruction *InstCombiner::visitCallSite(CallSite CS) {
+
   if (isAllocLikeFn(CS.getInstruction(), TLI))
     return visitAllocSite(*CS.getInstruction());
 
   bool Changed = false;
 
+  // Mark any parameters that are known to be non-null with the nonnull
+  // attribute.  This is helpful for inlining calls to functions with null
+  // checks on their arguments.
+  unsigned ArgNo = 0;
+  for (Value *V : CS.args()) {
+    if (!CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
+        isKnownNonNull(V)) {
+      AttributeSet AS = CS.getAttributes();
+      AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
+                           Attribute::NonNull);
+      CS.setAttributes(AS);
+      Changed = true;
+    }
+    ArgNo++;
+  }
+  assert(ArgNo == CS.arg_size() && "sanity check");
+
   // If the callee is a pointer to a function, attempt to move any casts to the
   // arguments of the call/invoke.
   Value *Callee = CS.getCalledValue();