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

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.

Reviewers: reames

Subscribers: llvm-commits

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

llvm-svn: 247356

2 files changed, 18 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index cc7d4be7a78..900953af6c6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1537,7 +1537,7 @@ Instruction *InstCombiner::visitCallSite(CallSite CS) {
   unsigned ArgNo = 0;
   for (Value *V : CS.args()) {
     if (!CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
-        isKnownNonNull(V)) {
+        isKnownNonNullAt(V, CS.getInstruction(), DT, TLI)) {
       AttributeSet AS = CS.getAttributes();
       AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
                            Attribute::NonNull);
diff --git a/llvm/test/Transforms/InstCombine/call_nonnull_arg.ll b/llvm/test/Transforms/InstCombine/call_nonnull_arg.ll
new file mode 100644
index 00000000000..cac53d3d47a
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/call_nonnull_arg.ll
@@ -0,0 +1,17 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; InstCombine should mark null-checked argument as nonnull at callsite
+declare void @dummy(i32*)
+
+define void @test(i32* %a) {
+; CHECK-LABEL: @test
+; CHECK: call void @dummy(i32* nonnull %a)
+entry:
+  %cond = icmp eq i32* %a, null
+  br i1 %cond, label %is_null, label %not_null
+not_null:
+  call void @dummy(i32* %a)
+  ret void
+is_null:
+  unreachable
+}