[llvm] [MemProf] Display backedges with dotted line in dot graphs (PR #128235)

[Teresa Johnson via llvm-commits]

https://github.com/teresajohnson updated https://github.com/llvm/llvm-project/pull/128235

>From 38736d96d0d16e2998f22b8267322b69d3aeda40 Mon Sep 17 00:00:00 2001
From: Teresa Johnson <tejohnson at google.com>
Date: Fri, 21 Feb 2025 13:07:24 -0800
Subject: [PATCH 1/2] [MemProf] Display backedges with dotted line in dot
 graphs

Add checking of this behavior in the postbuild dot graphs, facilitated
by PR128226 which marked these edges at the end of the graph building.
---
 .../IPO/MemProfContextDisambiguation.cpp           | 14 +++++++++-----
 llvm/test/ThinLTO/X86/memprof-recursive.ll         |  9 +++++++++
 .../MemProfContextDisambiguation/recursive.ll      |  9 +++++++++
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp b/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
index 705806b98f8da..85fb0b770f1ed 100644
--- a/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
+++ b/llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
@@ -3067,11 +3067,15 @@ struct DOTGraphTraits<const CallsiteContextGraph<DerivedCCG, FuncTy, CallTy> *>
                                        GraphType) {
     auto &Edge = *(ChildIter.getCurrent());
     auto Color = getColor(Edge->AllocTypes);
-    return (Twine("tooltip=\"") + getContextIds(Edge->ContextIds) + "\"" +
-            // fillcolor is the arrow head and color is the line
-            Twine(",fillcolor=\"") + Color + "\"" + Twine(",color=\"") + Color +
-            "\"")
-        .str();
+    std::string AttributeString =
+        (Twine("tooltip=\"") + getContextIds(Edge->ContextIds) + "\"" +
+         // fillcolor is the arrow head and color is the line
+         Twine(",fillcolor=\"") + Color + "\"" + Twine(",color=\"") + Color +
+         "\"")
+            .str();
+    if (Edge->IsBackedge)
+      AttributeString += ",style=\"dotted\"";
+    return AttributeString;
   }
 
   // Since the NodeOwners list includes nodes that are no longer connected to
diff --git a/llvm/test/ThinLTO/X86/memprof-recursive.ll b/llvm/test/ThinLTO/X86/memprof-recursive.ll
index e1a9084b583b9..a39f9216e8ab4 100644
--- a/llvm/test/ThinLTO/X86/memprof-recursive.ll
+++ b/llvm/test/ThinLTO/X86/memprof-recursive.ll
@@ -52,11 +52,20 @@
 ; RUN:  -r=%t.o,main,plx \
 ; RUN:  -r=%t.o,_Znam, \
 ; RUN:  -memprof-verify-ccg -memprof-verify-nodes -stats \
+; RUN:  -memprof-export-to-dot -memprof-dot-file-path-prefix=%t. \
 ; RUN:  -pass-remarks=memprof-context-disambiguation \
 ; RUN:  -o %t.out 2>&1 | FileCheck %s \
 ; RUN:  --check-prefix=ALLOW-RECUR-CALLSITES --check-prefix=ALLOW-RECUR-CONTEXTS \
 ; RUN:	--check-prefix=CLONE-RECUR-CALLSITES
 
+;; Check that the backedge was correctly detected and emitted to the dot file
+;; as a dotted edge.
+; RUN: cat %t.ccg.postbuild.dot | FileCheck %s --check-prefix=DOT
+; DOT-DAG: Node[[B:0x[a-f0-9]+]] {{.*}}_Z1Bi -\> _Z1Ci
+; DOT-DAG: Node[[C:0x[a-f0-9]+]] {{.*}}_Z1Ci -\> _Z1Bi
+; DOT-DAG: Node[[B]] -> Node[[C]]{{.*}}style="solid"
+; DOT-DAG: Node[[C]] -> Node[[B]]{{.*}}style="dotted"
+
 ;; Skipping recursive contexts should prevent spurious call to cloned version of
 ;; B from the context starting at memprof_recursive.cc:19:13, which is actually
 ;; recursive (until that support is added).
diff --git a/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll b/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll
index 1d09b1c1a0cb3..ed5c43ceaf375 100644
--- a/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll
+++ b/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll
@@ -64,11 +64,20 @@
 ;; Check the default behavior (clone recursive callsites).
 ; RUN: opt -passes=memprof-context-disambiguation -supports-hot-cold-new \
 ; RUN:  -memprof-verify-ccg -memprof-verify-nodes -stats \
+; RUN:  -memprof-export-to-dot -memprof-dot-file-path-prefix=%t. \
 ; RUN:  -pass-remarks=memprof-context-disambiguation \
 ; RUN:  %s -S 2>&1 | FileCheck %s \
 ; RUN:  --check-prefix=ALL --check-prefix=ALLOW-RECUR-CALLSITES --check-prefix=ALLOW-RECUR-CONTEXTS \
 ; RUN:  --check-prefix=CLONE-RECUR-CALLSITES
 
+;; Check that the backedge was correctly detected and emitted to the dot file
+;; as a dotted edge.
+; RUN: cat %t.ccg.postbuild.dot | FileCheck %s --check-prefix=DOT
+; DOT-DAG: Node[[B:0x[a-f0-9]+]] {{.*}}_Z1Bi -\> _Z1Ci
+; DOT-DAG: Node[[C:0x[a-f0-9]+]] {{.*}}_Z1Ci -\> _Z1Bi
+; DOT-DAG: Node[[B]] -> Node[[C]]{{.*}}style="solid"
+; DOT-DAG: Node[[C]] -> Node[[B]]{{.*}}style="dotted"
+
 ;; Skipping recursive contexts should prevent spurious call to cloned version of
 ;; B from the context starting at memprof_recursive.cc:19:13, which is actually
 ;; recursive (until that support is added).

>From 77bfe1227c5e2aa1ca41389998776428a0b19e23 Mon Sep 17 00:00:00 2001
From: Teresa Johnson <tejohnson at google.com>
Date: Fri, 21 Feb 2025 13:23:51 -0800
Subject: [PATCH 2/2] Fix tests

---
 llvm/test/ThinLTO/X86/memprof-recursive.ll                     | 1 -
 llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll | 1 -
 2 files changed, 2 deletions(-)

diff --git a/llvm/test/ThinLTO/X86/memprof-recursive.ll b/llvm/test/ThinLTO/X86/memprof-recursive.ll
index a39f9216e8ab4..00b2a0d79c1bf 100644
--- a/llvm/test/ThinLTO/X86/memprof-recursive.ll
+++ b/llvm/test/ThinLTO/X86/memprof-recursive.ll
@@ -63,7 +63,6 @@
 ; RUN: cat %t.ccg.postbuild.dot | FileCheck %s --check-prefix=DOT
 ; DOT-DAG: Node[[B:0x[a-f0-9]+]] {{.*}}_Z1Bi -\> _Z1Ci
 ; DOT-DAG: Node[[C:0x[a-f0-9]+]] {{.*}}_Z1Ci -\> _Z1Bi
-; DOT-DAG: Node[[B]] -> Node[[C]]{{.*}}style="solid"
 ; DOT-DAG: Node[[C]] -> Node[[B]]{{.*}}style="dotted"
 
 ;; Skipping recursive contexts should prevent spurious call to cloned version of
diff --git a/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll b/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll
index ed5c43ceaf375..e301fa03ea099 100644
--- a/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll
+++ b/llvm/test/Transforms/MemProfContextDisambiguation/recursive.ll
@@ -75,7 +75,6 @@
 ; RUN: cat %t.ccg.postbuild.dot | FileCheck %s --check-prefix=DOT
 ; DOT-DAG: Node[[B:0x[a-f0-9]+]] {{.*}}_Z1Bi -\> _Z1Ci
 ; DOT-DAG: Node[[C:0x[a-f0-9]+]] {{.*}}_Z1Ci -\> _Z1Bi
-; DOT-DAG: Node[[B]] -> Node[[C]]{{.*}}style="solid"
 ; DOT-DAG: Node[[C]] -> Node[[B]]{{.*}}style="dotted"
 
 ;; Skipping recursive contexts should prevent spurious call to cloned version of