[InstCombineCalls] Use isKnownNonNullAt() to check nullness of passing arguments...

Summary: This patch replaces isKnownNonNull() with isKnownNonNullAt() when checking nullness of passing arguments at callsite. In this way it can handle cases where the argument does not have nonnull attribute but has a dominating null check from the CFG. It also adds assertions in isKnownNonNull() and isKnownNonNullFromDominatingCondition() to make sure the value checked is pointer type (as defined in LLVM document). These assertions might trip failures in things which are not  covered under llvm/test, but fixes should be pretty obvious.

Reviewers: reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12779

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247587 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 7000210e1faad76c8276c643217256e63673e82d..21015507d2820a7dab35accbacc966a12f2f4fee 100644 (file)
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -3220,6 +3220,8 @@ bool llvm::mayBeMemoryDependent(const Instruction &I) {
 
 /// Return true if we know that the specified value is never null.
 bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
 
 /// Return true if we know that the specified value is never null.
 bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {

+  assert(V->getType()->isPointerTy() && "V must be pointer type");
+

   // Alloca never returns null, malloc might.
   if (isa<AllocaInst>(V)) return true;
 
   // Alloca never returns null, malloc might.
   if (isa<AllocaInst>(V)) return true;
 


@@ -3252,6 +3254,8 @@ bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
 static bool isKnownNonNullFromDominatingCondition(const Value *V,
                                                   const Instruction *CtxI,
                                                   const DominatorTree *DT) {
 static bool isKnownNonNullFromDominatingCondition(const Value *V,
                                                   const Instruction *CtxI,
                                                   const DominatorTree *DT) {

+  assert(V->getType()->isPointerTy() && "V must be pointer type");
+

   unsigned NumUsesExplored = 0;
   for (auto U : V->users()) {
     // Avoid massive lists
   unsigned NumUsesExplored = 0;
   for (auto U : V->users()) {
     // Avoid massive lists

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index c5f92a536b7ce24ceb9ba101da990cbfa156a347..ad606b0313852071716a63e9d8ca20a502df8378 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1583,8 +1583,8 @@ Instruction *InstCombiner::visitCallSite(CallSite CS) {
   // checks on their arguments.
   unsigned ArgNo = 0;
   for (Value *V : CS.args()) {
   // checks on their arguments.
   unsigned ArgNo = 0;
   for (Value *V : CS.args()) {

-    if (!CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
-        isKnownNonNull(V)) {
+    if (V->getType()->isPointerTy() && !CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
+        isKnownNonNullAt(V, CS.getInstruction(), DT, TLI)) {

       AttributeSet AS = CS.getAttributes();
       AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
                            Attribute::NonNull);
       AttributeSet AS = CS.getAttributes();
       AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
                            Attribute::NonNull);

diff --git a/test/Transforms/InstCombine/call_nonnull_arg.ll b/test/Transforms/InstCombine/call_nonnull_arg.ll
new file mode 100644 (file)
index 0000000..b10411f
--- /dev/null
+++ b/test/Transforms/InstCombine/call_nonnull_arg.ll
@@ -0,0 +1,20 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; InstCombine should mark null-checked argument as nonnull at callsite
+declare void @dummy(i32*, i32)
+
+define void @test(i32* %a, i32 %b) {
+; CHECK-LABEL: @test
+; CHECK: call void @dummy(i32* nonnull %a, i32 %b)
+entry:
+  %cond1 = icmp eq i32* %a, null
+  br i1 %cond1, label %dead, label %not_null
+not_null:
+  %cond2 = icmp eq i32 %b, 0
+  br i1 %cond2, label %dead, label %not_zero
+not_zero:
+  call void @dummy(i32* %a, i32 %b)
+  ret void
+dead:
+  unreachable
+}