[Attributor][FIX] NoCapture is not a subsuming property

We cannot look at the subsuming positions and take their nocapture bit
as shown with the two tests for which we derived nocapture on the call
site argument and readonly on the argument of the second before.

2 files changed, 43 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index a0677c194f1..6f0a4a85890 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -3131,7 +3131,16 @@ struct AANoCaptureImpl : public AANoCapture {
 
   /// See AbstractAttribute::initialize(...).
   void initialize(Attributor &A) override {
-    AANoCapture::initialize(A);
+    if (hasAttr(getAttrKind(), /* IgnoreSubsumingPositions */ true)) {
+      indicateOptimisticFixpoint();
+      return;
+    }
+    Function *AnchorScope = getAnchorScope();
+    if (isFnInterfaceKind() &&
+        (!AnchorScope || !AnchorScope->hasExactDefinition())) {
+      indicatePessimisticFixpoint();
+      return;
+    }
 
     // You cannot "capture" null in the default address space.
     if (isa<ConstantPointerNull>(getAssociatedValue()) &&
@@ -3140,13 +3149,11 @@ struct AANoCaptureImpl : public AANoCapture {
       return;
     }
 
-    const IRPosition &IRP = getIRPosition();
-    const Function *F =
-        getArgNo() >= 0 ? IRP.getAssociatedFunction() : IRP.getAnchorScope();
+    const Function *F = getArgNo() >= 0 ? getAssociatedFunction() : AnchorScope;
 
     // Check what state the associated function can actually capture.
     if (F)
-      determineFunctionCaptureCapabilities(IRP, *F, *this);
+      determineFunctionCaptureCapabilities(getIRPosition(), *F, *this);
     else
       indicatePessimisticFixpoint();
   }
diff --git a/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll b/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
index 18a4f767147..ec7db076b36 100644
--- a/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
+++ b/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
@@ -437,4 +437,35 @@ entry:
   ret i32* %call
 }
 
+
+declare i32* @unknown_i32p(i32*)
+define void @nocapture_is_not_subsumed_1(i32* nocapture %b) {
+; CHECK-LABEL: define {{[^@]+}}@nocapture_is_not_subsumed_1
+; CHECK-SAME: (i32* nocapture [[B:%.*]])
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CALL:%.*]] = call i32* @unknown_i32p(i32* [[B:%.*]])
+; CHECK-NEXT:    store i32 0, i32* [[CALL]]
+; CHECK-NEXT:    ret void
+;
+entry:
+  %call = call i32* @unknown_i32p(i32* %b)
+  store i32 0, i32* %call
+  ret void
+}
+
+declare i32* @readonly_i32p(i32*) readonly
+define void @nocapture_is_not_subsumed_2(i32* nocapture %b) {
+; CHECK-LABEL: define {{[^@]+}}@nocapture_is_not_subsumed_2
+; CHECK-SAME: (i32* nocapture [[B:%.*]])
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CALL:%.*]] = call i32* @readonly_i32p(i32* readonly [[B:%.*]])
+; CHECK-NEXT:    store i32 0, i32* [[CALL]]
+; CHECK-NEXT:    ret void
+;
+entry:
+  %call = call i32* @readonly_i32p(i32* %b)
+  store i32 0, i32* %call
+  ret void
+}
+
 attributes #0 = { noinline nounwind uwtable }