[llvm] [ctx_prof] Handle case when no root is in this Module. (PR #107463)

[Mircea Trofin via llvm-commits]

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@@ -0,0 +1,60 @@
+; REQUIRES: x86_64-linux
+;
+; RUN: rm -rf %t
+; RUN: split-file %s %t
+; RUN: llvm-ctxprof-util fromJSON --input=%t/profile.json --output=%t/profile.ctxprofdata
+; RUN: opt -passes='require<ctx-prof-analysis>,print<ctx-prof-analysis>' -ctx-profile-printer-level=everything \
+; RUN:   %t/example.ll -S 2>&1 | FileCheck %s
+
+; CHECK: No contextual profile was provided
+;
+; This is the reference profile, laid out in the format the json formatter will
+; output it from opt.
+;--- profile.json
+[
+  {
+    "Counters": [
+      9
+    ],
+    "Guid": 12341
+  },
+  {
+    "Counters": [
+      5
+    ],
+    "Guid": 12074870348631550642
+  },
+  {
+    "Callsites": [
+      [
+        {
+          "Counters": [
+            6,
+            7
+          ],
+          "Guid": 728453322856651412
+        }
+      ]
+    ],
+    "Counters": [
+      1
+    ],
+    "Guid": 11872291593386833696
+  }
+]
+;--- example.ll
+declare void @bar()
+
+define void @an_entrypoint(i32 %a) {
+  %t = icmp eq i32 %a, 0
+  br i1 %t, label %yes, label %no
+
+yes:
+  call void @bar()
+  ret void
+no:
+  ret void
+}
+
+attributes #0 = { noinline }
+!0 = !{ i64 1000 }
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mtrofin wrote:

it is now - the goal is to make sure it's clearly different from the given root.

https://github.com/llvm/llvm-project/pull/107463