[llvm] [FuncAttrs][LTO] Relax norecurse attribute inference during postlink LTO (PR #158608)

[David Sherwood via llvm-commits]

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@@ -0,0 +1,135 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-attributes --version 5
+; RUN: opt < %s -passes=norecurse-lto-inference -S | FileCheck %s
+
+; This test includes a call graph with a self recursive function.
+; The purpose of this is to check that norecurse is added to functions
+; which have a self-recursive function in the call-chain.
+; The call-chain in this test is as follows
+; main -> bob -> callee1 -> callee2 -> callee3 -> callee4 -> callee5
+; where callee5 is self recursive.
+
+ at x = dso_local global i32 4, align 4
+ at y = dso_local global i32 2, align 4
+
+define internal void @callee6() {
+; CHECK: Function Attrs: norecurse
+; CHECK-LABEL: define internal void @callee6(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[TMP0:%.*]] = load volatile i32, ptr @y, align 4
+; CHECK-NEXT:    [[INC:%.*]] = add nsw i32 [[TMP0]], 1
+; CHECK-NEXT:    store volatile i32 [[INC]], ptr @y, align 4
+; CHECK-NEXT:    ret void
+;
+entry:
+  %0 = load volatile i32, ptr @y, align 4
+  %inc = add nsw i32 %0, 1
+  store volatile i32 %inc, ptr @y, align 4
+  ret void
+}
+
+define internal void @callee5(i32 noundef %x) {
+; CHECK-LABEL: define internal void @callee5(
+; CHECK-SAME: i32 noundef [[X:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[X]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label %[[IF_THEN:.*]], label %[[IF_END:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    tail call void @callee5(i32 noundef [[X]])
+; CHECK-NEXT:    br label %[[IF_END]]
+; CHECK:       [[IF_END]]:
+; CHECK-NEXT:    tail call void @callee6()
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp sgt i32 %x, 0
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  tail call void @callee5(i32 noundef %x)
+  br label %if.end
+
+if.end:                                           ; preds = %if.then, %entry
+  tail call void @callee6()
+  ret void
+}
+
+define internal void @callee4() {
+; CHECK: Function Attrs: norecurse
+; CHECK-LABEL: define internal void @callee4(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[TMP0:%.*]] = load volatile i32, ptr @x, align 4
+; CHECK-NEXT:    tail call void @callee5(i32 noundef [[TMP0]])
+; CHECK-NEXT:    ret void
+;
+entry:
+  %0 = load volatile i32, ptr @x, align 4
+  tail call void @callee5(i32 noundef %0)
+  ret void
+}
+
+define internal void @callee3() {
+; CHECK: Function Attrs: norecurse
+; CHECK-LABEL: define internal void @callee3(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    tail call void @callee4()
+; CHECK-NEXT:    ret void
+;
+entry:
+  tail call void @callee4()
+  ret void
+}
+
+define internal void @callee2() {
+; CHECK: Function Attrs: norecurse
+; CHECK-LABEL: define internal void @callee2(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    tail call void @callee3()
+; CHECK-NEXT:    ret void
+;
+entry:
+  tail call void @callee3()
+  ret void
+}
+
+define internal void @callee1() {
+; CHECK: Function Attrs: norecurse
+; CHECK-LABEL: define internal void @callee1(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    tail call void @callee2()
+; CHECK-NEXT:    ret void
+;
+entry:
+  tail call void @callee2()
+  ret void
+}
+
+define internal void @bob() {
+; CHECK: Function Attrs: norecurse
+; CHECK-LABEL: define internal void @bob(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    tail call void @callee1()
+; CHECK-NEXT:    ret void
+;
+entry:
+  tail call void @callee1()
+  ret void
+}
+
+define dso_local noundef i32 @main() norecurse {
----------------
david-arm wrote:

Is the `noundef` needed here?

Also do we even need `norecurse`? Since all the callees lower down the stack only ever invoke internal functions I'd expect it to just work the same.

https://github.com/llvm/llvm-project/pull/158608