Make sure we don't increase pre-existing captures attributes

Author: nikic

llvm/lib/Transforms/IPO/FunctionAttrs.cpp

@@ -1320,8 +1320,9 @@ static void addArgumentAttrs(const SCCNodeSet &SCCNodes,
       if (ArgumentSCC[0]->Uses.size() == 1 &&
           ArgumentSCC[0]->Uses[0] == ArgumentSCC[0]) {
         Argument *A = ArgumentSCC[0]->Definition;
-        CaptureInfo NewCI = ArgumentSCC[0]->CC;
-        if (NewCI != A->getAttributes().getCaptureInfo()) {
+        CaptureInfo OrigCI = A->getAttributes().getCaptureInfo();
+        CaptureInfo NewCI = CaptureInfo(ArgumentSCC[0]->CC) & OrigCI;
+        if (NewCI != OrigCI) {
           A->addAttr(Attribute::getWithCaptureInfo(A->getContext(), NewCI));
           addCapturesStat(NewCI);
           Changed.insert(A->getParent());
@@ -1361,10 +1362,13 @@ static void addArgumentAttrs(const SCCNodeSet &SCCNodes,
     if (!capturesAll(CC)) {
       for (ArgumentGraphNode *N : ArgumentSCC) {
         Argument *A = N->Definition;
-        CaptureInfo CI = N->CC | CC;
-        A->addAttr(Attribute::getWithCaptureInfo(A->getContext(), CI));
-        addCapturesStat(CI);
-        Changed.insert(A->getParent());
+        CaptureInfo OrigCI = A->getAttributes().getCaptureInfo();
+        CaptureInfo NewCI = CaptureInfo(N->CC | CC) & OrigCI;
+        if (NewCI != OrigCI) {
+          A->addAttr(Attribute::getWithCaptureInfo(A->getContext(), NewCI));
+          addCapturesStat(NewCI);
+          Changed.insert(A->getParent());
+        }
       }
     }
 

llvm/test/Transforms/FunctionAttrs/nocapture.ll

@@ -1018,5 +1018,72 @@ else:
   ret ptr %p
 }
 
+define i1 @improve_existing_captures(ptr captures(address) %p) {
+; FNATTRS: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; FNATTRS-LABEL: define i1 @improve_existing_captures
+; FNATTRS-SAME: (ptr readnone captures(address_is_null) [[P:%.*]]) #[[ATTR0]] {
+; FNATTRS-NEXT:    [[CMP:%.*]] = icmp eq ptr [[P]], null
+; FNATTRS-NEXT:    ret i1 [[CMP]]
+;
+; ATTRIBUTOR: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; ATTRIBUTOR-LABEL: define i1 @improve_existing_captures
+; ATTRIBUTOR-SAME: (ptr nofree readnone captures(address) [[P:%.*]]) #[[ATTR0]] {
+; ATTRIBUTOR-NEXT:    [[CMP:%.*]] = icmp eq ptr [[P]], null
+; ATTRIBUTOR-NEXT:    ret i1 [[CMP]]
+;
+  %cmp = icmp eq ptr %p, null
+  ret i1 %cmp
+}
+
+define void @dont_increase_existing_captures(ptr captures(address) %p) {
+; COMMON-LABEL: define void @dont_increase_existing_captures
+; COMMON-SAME: (ptr captures(address) [[P:%.*]]) {
+; COMMON-NEXT:    call void @capture(ptr [[P]])
+; COMMON-NEXT:    ret void
+;
+  call void @capture(ptr %p)
+  ret void
+}
+
+define void @dont_increase_existing_captures_trivial_scc(ptr captures(address) %p) {
+; COMMON-LABEL: define void @dont_increase_existing_captures_trivial_scc
+; COMMON-SAME: (ptr captures(address) [[P:%.*]]) {
+; COMMON-NEXT:    call void @capture(ptr captures(address, read_provenance) [[P]])
+; COMMON-NEXT:    call void @dont_increase_existing_captures_trivial_scc(ptr [[P]])
+; COMMON-NEXT:    ret void
+;
+  call void @capture(ptr captures(address, read_provenance) %p)
+  call void @dont_increase_existing_captures_trivial_scc(ptr %p)
+  ret void
+}
+
+define void @dont_increase_existing_captures_scc1(ptr captures(address) %p) {
+; COMMON-LABEL: define void @dont_increase_existing_captures_scc1
+; COMMON-SAME: (ptr captures(address) [[P:%.*]]) {
+; COMMON-NEXT:    call void @dont_increase_existing_captures_scc2(ptr [[P]])
+; COMMON-NEXT:    ret void
+;
+  call void @dont_increase_existing_captures_scc2(ptr %p)
+  ret void
+}
+
+define void @dont_increase_existing_captures_scc2(ptr %p) {
+; FNATTRS-LABEL: define void @dont_increase_existing_captures_scc2
+; FNATTRS-SAME: (ptr captures(address, read_provenance) [[P:%.*]]) {
+; FNATTRS-NEXT:    call void @capture(ptr captures(address, read_provenance) [[P]])
+; FNATTRS-NEXT:    call void @dont_increase_existing_captures_scc1(ptr [[P]])
+; FNATTRS-NEXT:    ret void
+;
+; ATTRIBUTOR-LABEL: define void @dont_increase_existing_captures_scc2
+; ATTRIBUTOR-SAME: (ptr [[P:%.*]]) {
+; ATTRIBUTOR-NEXT:    call void @capture(ptr captures(address, read_provenance) [[P]])
+; ATTRIBUTOR-NEXT:    call void @dont_increase_existing_captures_scc1(ptr [[P]])
+; ATTRIBUTOR-NEXT:    ret void
+;
+  call void @capture(ptr captures(address, read_provenance) %p)
+  call void @dont_increase_existing_captures_scc1(ptr %p)
+  ret void
+}
+
 declare ptr @llvm.launder.invariant.group.p0(ptr)
 declare ptr @llvm.strip.invariant.group.p0(ptr)