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

llvm/include/llvm/IR/CallSite.h

@@ -27,6 +27,7 @@
 #define LLVM_IR_CALLSITE_H
 
 #include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/iterator_range.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Instructions.h"
@@ -150,6 +151,9 @@ public:
   }
 
   IterTy arg_end() const { return (*this)->op_end() - getArgumentEndOffset(); }
+  iterator_range<IterTy> args() const {
+    return iterator_range<IterTy>(arg_begin(), arg_end());
+  }
   bool arg_empty() const { return arg_end() == arg_begin(); }
   unsigned arg_size() const { return unsigned(arg_end() - arg_begin()); }
 

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();

llvm/test/CodeGen/NVPTX/intrin-nocapture.ll

@@ -11,7 +11,7 @@ declare i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32*)
 ; CHECK: @bar
 define void @bar() {
   %t1 = alloca i32
-; CHECK: call i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32* %t1)
+; CHECK: call i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32* nonnull %t1)
 ; CHECK-NEXT: store i32 10, i32* %t1
   %t2 = call i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32* %t1)
   store i32 10, i32* %t1

llvm/test/Transforms/Inline/byval-tail-call.ll

@@ -33,7 +33,7 @@ define void @frob(i32* %x) {
 ; CHECK: %[[POS:.*]] = alloca i32
 ; CHECK: %[[VAL:.*]] = load i32, i32* %x
 ; CHECK: store i32 %[[VAL]], i32* %[[POS]]
-; CHECK: {{^ *}}call void @ext(i32* %[[POS]]
+; CHECK: {{^ *}}call void @ext(i32* nonnull %[[POS]]
 ; CHECK: tail call void @ext(i32* null)
 ; CHECK: ret void
   tail call void @qux(i32* byval %x)

llvm/test/Transforms/InstCombine/select.ll

@@ -1265,7 +1265,7 @@ define i32 @test77(i1 %flag, i32* %x) {
 ; load does.
 ; CHECK-LABEL: @test77(
 ; CHECK: %[[A:.*]] = alloca i32, align 1
-; CHECK: call void @scribble_on_i32(i32* %[[A]])
+; CHECK: call void @scribble_on_i32(i32* nonnull %[[A]])
 ; CHECK: store i32 0, i32* %x
 ; CHECK: %[[P:.*]] = select i1 %flag, i32* %[[A]], i32* %x
 ; CHECK: load i32, i32* %[[P]]