[llvm] [PredicateInfo] Reformat PT_Switch's annotation as valid comments (PR #165249)

[Kunqiu Chen via llvm-commits]

https://github.com/Camsyn created https://github.com/llvm/llvm-project/pull/165249

Previously, PredicateInfo brutally annotated `PT_Switch` as follows:
```python
f'"; switch predicate info ... CaseValue: ... Switch: {*PS->Switch} Edge: ... RenamedOp: ..."'
```

However, the `switch` instruction in LLVM might cross >1 lines, leading to the annotation of `PT_Switch` being **illegal comments**, e.g., 
```LLVM
; switch predicate info { CaseValue: i32 1 Switch:  switch i32 %x, label %default [
    i32 0, label %case0
    i32 1, label %case1
    i32 2, label %case0
    i32 3, label %case3
    i32 4, label %default
  ] Edge: [label %sw,label %case1], RenamedOp: %x }
  x.0 = bitcast i32 %x to i32
```

This patch reformats the `PT_Switch`'s annotation as follows:
```python
f'"; switch predicate info ... CaseValue: ... Edge: ... Switch: \n{with_lines_commented(*PS->Switch)}\n; RenamedOp: ..."'
```
, e.g., 

```LLVM
; switch predicate info { CaseValue: i32 1 Edge: [label %sw,label %case1] Switch:
;     switch i32 %x, label %default [
;       i32 0, label %case0
;       i32 1, label %case1
;       i32 2, label %case0
;       i32 3, label %case3
;       i32 4, label %default
;     ]
; , RenamedOp: %x }
  x.0 = bitcast i32 %x to i32
```

` RenamedOp: ...` is still the trailing content of the annotation to keep consistency with the annotation of `PT_Assme`/`PT_Bracnh`.

>From 15b589712ea072d47dffc23bbfb266e7c540f7e0 Mon Sep 17 00:00:00 2001
From: Camsyn <camsyn at foxmail.com>
Date: Mon, 27 Oct 2025 21:11:29 +0800
Subject: [PATCH 1/2] Reformat PT_Switch annotation to make it as legal
 comments

---
 llvm/lib/Transforms/Utils/PredicateInfo.cpp | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/PredicateInfo.cpp b/llvm/lib/Transforms/Utils/PredicateInfo.cpp
index 978d5a25a57c8..4f0f756ecc3ca 100644
--- a/llvm/lib/Transforms/Utils/PredicateInfo.cpp
+++ b/llvm/lib/Transforms/Utils/PredicateInfo.cpp
@@ -14,6 +14,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/IR/AssemblyAnnotationWriter.h"
 #include "llvm/IR/Dominators.h"
@@ -25,6 +26,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/DebugCounter.h"
 #include "llvm/Support/FormattedStream.h"
+#include "llvm/Support/raw_ostream.h"
 #define DEBUG_TYPE "predicateinfo"
 using namespace llvm;
 using namespace PatternMatch;
@@ -812,11 +814,23 @@ class PredicateInfoAnnotatedWriter : public AssemblyAnnotationWriter {
         OS << "]";
       } else if (const auto *PS = dyn_cast<PredicateSwitch>(PI)) {
         OS << "; switch predicate info { CaseValue: " << *PS->CaseValue
-           << " Switch:" << *PS->Switch << " Edge: [";
+           << " Edge: [";
         PS->From->printAsOperand(OS);
         OS << ",";
         PS->To->printAsOperand(OS);
-        OS << "]";
+        OS << "] Switch:\n";
+        // A switch might cross > 1 lines, we should add the comment prefix ';'
+        // for each line
+        std::string SwitchStr;
+        {
+          llvm::raw_string_ostream SwitchOS(SwitchStr);
+          PS->Switch->print(SwitchOS);
+        }
+        SmallVector<StringRef, 8> Lines;
+        StringRef(SwitchStr).split(Lines, '\n');
+        for (const auto &Line : Lines)
+          OS << ";   " << Line << "\n";
+        OS << "; ";
       } else if (const auto *PA = dyn_cast<PredicateAssume>(PI)) {
         OS << "; assume predicate info {"
            << " Comparison:" << *PA->Condition;

>From ac779d741dc82fbfb92493473dae4cf72c60c286 Mon Sep 17 00:00:00 2001
From: Camsyn <camsyn at foxmail.com>
Date: Mon, 27 Oct 2025 21:25:31 +0800
Subject: [PATCH 2/2] Regenerate the test

---
 .../Transforms/Util/PredicateInfo/condprop.ll | 20 +++++++------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/llvm/test/Transforms/Util/PredicateInfo/condprop.ll b/llvm/test/Transforms/Util/PredicateInfo/condprop.ll
index 0235732b95a83..256d0d908ec1e 100644
--- a/llvm/test/Transforms/Util/PredicateInfo/condprop.ll
+++ b/llvm/test/Transforms/Util/PredicateInfo/condprop.ll
@@ -133,19 +133,13 @@ define void @test4(i1 %b, i32 %x) {
 ; CHECK-LABEL: @test4(
 ; CHECK-NEXT:    br i1 [[B:%.*]], label [[SW:%.*]], label [[CASE3:%.*]]
 ; CHECK:       sw:
-; CHECK:         i32 0, label [[CASE0:%.*]]
-; CHECK-NEXT:    i32 1, label [[CASE1:%.*]]
-; CHECK-NEXT:    i32 2, label [[CASE0]]
-; CHECK-NEXT:    i32 3, label [[CASE3]]
-; CHECK-NEXT:    i32 4, label [[DEFAULT:%.*]]
-; CHECK-NEXT:    ] Edge: [label [[SW]],label %case1], RenamedOp: [[X:%.*]] }
-; CHECK-NEXT:    [[X_0:%.*]] = bitcast i32 [[X]] to i32
-; CHECK-NEXT:    switch i32 [[X]], label [[DEFAULT]] [
-; CHECK-NEXT:    i32 0, label [[CASE0]]
-; CHECK-NEXT:    i32 1, label [[CASE1]]
-; CHECK-NEXT:    i32 2, label [[CASE0]]
-; CHECK-NEXT:    i32 3, label [[CASE3]]
-; CHECK-NEXT:    i32 4, label [[DEFAULT]]
+; CHECK:         [[X_0:%.*]] = bitcast i32 [[X:%.*]] to i32
+; CHECK-NEXT:    switch i32 [[X]], label [[DEFAULT:%.*]] [
+; CHECK-NEXT:      i32 0, label [[CASE0:%.*]]
+; CHECK-NEXT:      i32 1, label [[CASE1:%.*]]
+; CHECK-NEXT:      i32 2, label [[CASE0]]
+; CHECK-NEXT:      i32 3, label [[CASE3]]
+; CHECK-NEXT:      i32 4, label [[DEFAULT]]
 ; CHECK-NEXT:    ]
 ; CHECK:       default:
 ; CHECK-NEXT:    call void @bar(i32 [[X]])