From ca857efb5b7308d5dda621685a766da6960a8157 Mon Sep 17 00:00:00 2001
From: Igor Laevsky <igmyrj@gmail.com>
Date: Tue, 15 Sep 2015 17:51:50 +0000
Subject: [PATCH] [CorrelatedValuePropagation] Infer nonnull attributes

LazuValueInfo can prove that value is nonnull based on the context information.
Make use of this ability to infer nonnull attributes for the call arguments.

Differential Revision: http://reviews.llvm.org/D12836



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247707 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/CorrelatedValuePropagation.cpp     | 31 +++++++++++++++
 .../CorrelatedValuePropagation/non-null.ll    | 39 +++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 8706dfee73d..ac12427015d 100644
--- a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -44,6 +44,7 @@ namespace {
     bool processMemAccess(Instruction *I);
     bool processCmp(CmpInst *C);
     bool processSwitch(SwitchInst *SI);
+    bool processCallSite(CallSite CS);
 
   public:
     static char ID;
@@ -309,6 +310,32 @@ bool CorrelatedValuePropagation::processSwitch(SwitchInst *SI) {
   return Changed;
 }
 
+/// processCallSite - Infer nonnull attributes for the arguments at the
+/// specified callsite.
+bool CorrelatedValuePropagation::processCallSite(CallSite CS) {
+  bool Changed = false;
+
+  unsigned ArgNo = 0;
+  for (Value *V : CS.args()) {
+    PointerType *Type = dyn_cast<PointerType>(V->getType());
+
+    if (Type && !CS.paramHasAttr(ArgNo + 1, Attribute::NonNull) &&
+        LVI->getPredicateAt(ICmpInst::ICMP_EQ, V,
+                            ConstantPointerNull::get(Type),
+                            CS.getInstruction()) == LazyValueInfo::False) {
+      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");
+
+  return Changed;
+}
+
 bool CorrelatedValuePropagation::runOnFunction(Function &F) {
   if (skipOptnoneFunction(F))
     return false;
@@ -336,6 +363,10 @@ bool CorrelatedValuePropagation::runOnFunction(Function &F) {
       case Instruction::Store:
         BBChanged |= processMemAccess(II);
         break;
+      case Instruction::Call:
+      case Instruction::Invoke:
+        BBChanged |= processCallSite(CallSite(II));
+        break;
       }
     }
 
diff --git a/test/Transforms/CorrelatedValuePropagation/non-null.ll b/test/Transforms/CorrelatedValuePropagation/non-null.ll
index 6bb8bb07c45..a24dfb67ca1 100644
--- a/test/Transforms/CorrelatedValuePropagation/non-null.ll
+++ b/test/Transforms/CorrelatedValuePropagation/non-null.ll
@@ -101,3 +101,42 @@ bb:
 ; CHECK: KEEP2
   ret void
 }
+
+declare void @test10_helper(i8* %arg1, i8* %arg2, i32 %non-pointer-arg)
+define void @test10(i8* %arg1, i8* %arg2, i32 %non-pointer-arg) {
+; CHECK-LABEL: @test10
+entry:
+  %is_null = icmp eq i8* %arg1, null
+  br i1 %is_null, label %null, label %non_null
+
+non_null:
+  call void @test10_helper(i8* %arg1, i8* %arg2, i32 %non-pointer-arg)
+  ; CHECK: call void @test10_helper(i8* nonnull %arg1, i8* %arg2, i32 %non-pointer-arg)
+  br label %null
+
+null:
+  call void @test10_helper(i8* %arg1, i8* %arg2, i32 %non-pointer-arg)
+  ; CHECK: call void @test10_helper(i8* %arg1, i8* %arg2, i32 %non-pointer-arg)
+  ret void
+}
+
+declare void @test11_helper(i8* %arg)
+define void @test11(i8* %arg1, i8** %arg2) {
+; CHECK-LABEL: @test11
+entry:
+  %is_null = icmp eq i8* %arg1, null
+  br i1 %is_null, label %null, label %non_null
+
+non_null:
+  br label %merge
+
+null:
+  %another_arg = alloca i8
+  br label %merge
+
+merge:
+  %merged_arg = phi i8* [%another_arg, %null], [%arg1, %non_null]
+  call void @test11_helper(i8* %merged_arg)
+  ; CHECK: call void @test11_helper(i8* nonnull %merged_arg)
+  ret void
+}
-- 
2.34.1