[llvm] [Kaleidoscope] Add mem2reg pass to function pass manager (PR #119707)

[via llvm-commits]

https://github.com/aidint created https://github.com/llvm/llvm-project/pull/119707

Kaleidoscope has switched to new pass manager before (#72324), but both code and tutorial document have some missing parts.

This pull request fixes the following problems:
1. Adds `PromotePass` to the function pass manager. This pass was removed during the switch from legacy pass manager to the new pass manager. 
2. Syncs the tutorial with the code.

>From 9f0ba6bffe6439b81015375bd28ba49d1a0754b2 Mon Sep 17 00:00:00 2001
From: aidint <at.aidin at gmail.com>
Date: Thu, 12 Dec 2024 15:14:51 +0100
Subject: [PATCH] Add mem2reg pass to the function pass manager

---
 llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst | 8 ++++----
 llvm/examples/Kaleidoscope/Chapter7/toy.cpp               | 4 +++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst b/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst
index 8fd4c39d3ff47b..ed1dea2324918b 100644
--- a/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst
+++ b/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst
@@ -336,7 +336,7 @@ the function:
     /// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
     /// the function.  This is used for mutable variables etc.
     static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
-                                              const std::string &VarName) {
+                                              StringRef VarName) {
       IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
                      TheFunction->getEntryBlock().begin());
       return TmpB.CreateAlloca(Type::getDoubleTy(*TheContext), nullptr,
@@ -440,11 +440,11 @@ get good codegen once again:
 .. code-block:: c++
 
         // Promote allocas to registers.
-        TheFPM->add(createPromoteMemoryToRegisterPass());
+        TheFPM->addPass(PromotePass());
         // Do simple "peephole" optimizations and bit-twiddling optzns.
-        TheFPM->add(createInstructionCombiningPass());
+        TheFPM->addPass(InstCombinePass());
         // Reassociate expressions.
-        TheFPM->add(createReassociatePass());
+        TheFPM->addPass(ReassociatePass());
         ...
 
 It is interesting to see what the code looks like before and after the
diff --git a/llvm/examples/Kaleidoscope/Chapter7/toy.cpp b/llvm/examples/Kaleidoscope/Chapter7/toy.cpp
index 68208c4f3394ab..374f2c03b48e02 100644
--- a/llvm/examples/Kaleidoscope/Chapter7/toy.cpp
+++ b/llvm/examples/Kaleidoscope/Chapter7/toy.cpp
@@ -21,7 +21,7 @@
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar/Reassociate.h"
 #include "llvm/Transforms/Scalar/SimplifyCFG.h"
-#include "llvm/Transforms/Utils.h"
+#include "llvm/Transforms/Utils/Mem2Reg.h"
 #include <algorithm>
 #include <cassert>
 #include <cctype>
@@ -1142,6 +1142,8 @@ static void InitializeModuleAndManagers() {
   TheSI->registerCallbacks(*ThePIC, TheMAM.get());
 
   // Add transform passes.
+  // Promote allocas to registers.
+  TheFPM->addPass(PromotePass());
   // Do simple "peephole" optimizations and bit-twiddling optzns.
   TheFPM->addPass(InstCombinePass());
   // Reassociate expressions.