[llvm] Attributor: Don't rely on use_empty for constants (PR #137218)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

This allows inferring noalias on a null argument parameter. This
avoids a non-NFC diff in a future change.

---
Full diff: https://github.com/llvm/llvm-project/pull/137218.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/IPO/AttributorAttributes.cpp (+1-1) 
- (modified) llvm/test/Transforms/Attributor/issue87856.ll (+1-1) 


``````````diff
diff --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index ac56df3823e20..1032dede7cb36 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -5746,7 +5746,7 @@ bool AANoCapture::isImpliedByIR(Attributor &A, const IRPosition &IRP,
   assert(ImpliedAttributeKind == Attribute::Captures &&
          "Unexpected attribute kind");
   Value &V = IRP.getAssociatedValue();
-  if (!IRP.isArgumentPosition())
+  if (!isa<Constant>(V) && !IRP.isArgumentPosition())
     return V.use_empty();
 
   // You cannot "capture" null in the default address space.
diff --git a/llvm/test/Transforms/Attributor/issue87856.ll b/llvm/test/Transforms/Attributor/issue87856.ll
index 4990ef909dfaa..592ec33a31369 100644
--- a/llvm/test/Transforms/Attributor/issue87856.ll
+++ b/llvm/test/Transforms/Attributor/issue87856.ll
@@ -4,7 +4,7 @@
 define void @null_ptr_is_valid_call_with_null() #0 {
 ; CHECK-LABEL: define void @null_ptr_is_valid_call_with_null(
 ; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
-; CHECK-NEXT:    call void @store_as0(ptr nofree noundef writeonly null) #[[ATTR4:[0-9]+]]
+; CHECK-NEXT:    call void @store_as0(ptr noalias nofree noundef writeonly null) #[[ATTR4:[0-9]+]]
 ; CHECK-NEXT:    ret void
 ;
   call void @store_as0(ptr null)

``````````

</details>


https://github.com/llvm/llvm-project/pull/137218