[PATCH] D12836: [CorrelatedValuePropagation] Infer nonnull attributes

[Igor Laevsky via llvm-commits]

igor-laevsky created this revision.
igor-laevsky added reviewers: reames, hfinkel.
igor-laevsky added a subscriber: llvm-commits.
igor-laevsky set the repository for this revision to rL LLVM.

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.

There is almost similar code inside InstCombine. However it uses isKnownNonNull which is less precise than LazyValueInfo.

Repository:
  rL LLVM

http://reviews.llvm.org/D12836

Files:
  lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
  test/Transforms/CorrelatedValuePropagation/non-null.ll

Index: test/Transforms/CorrelatedValuePropagation/non-null.ll
===================================================================
--- test/Transforms/CorrelatedValuePropagation/non-null.ll
+++ test/Transforms/CorrelatedValuePropagation/non-null.ll
@@ -101,3 +101,20 @@
 ; 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) {
+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
+}
Index: lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
===================================================================
--- lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -44,6 +44,7 @@
     bool processMemAccess(Instruction *I);
     bool processCmp(CmpInst *C);
     bool processSwitch(SwitchInst *SI);
+    bool processCallSite(CallSite CS);
 
   public:
     static char ID;
@@ -309,6 +310,32 @@
   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 @@
       case Instruction::Store:
         BBChanged |= processMemAccess(II);
         break;
+      case Instruction::Call:
+      case Instruction::Invoke:
+        BBChanged |= processCallSite(CallSite(II));
+        break;
       }
     }
 


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