[llvm] Move StringExtras.h include from Error.h to Error.cpp

[IncludeGuardian]

Summary

Move the implementation of the toString function from llvm/Support/Error.h to the source file,
which allows us to move #include "llvm/ADT/StringExtras.h" to the source file as well.

As Error.h is present in a large number of translation units this means we are unnecessarily bringing in the
contents of StringExtras.h - itself a large file with lots of includes - and slowing down compilation.

Includes have been added to source/header files that are needed but were being transitively included. The
majority needed StringExtras.h but a few only required a smaller header: APInt.h, APSInt.h, or
SmallString.h.

This reduces the total number of preprocessing tokens across the LLVM source files in lib from (roughly)
1,920,413,050 to 1,903,629,230 - a reduction of ~0.87%. This should result in a small improvement in compilation
time.

[IncludeGuardian]

This was found with IncludeGuardian 0.0.8.

The line that suggested this can be found in the output here.

The count of preprocessing tokens before and after this change can be found in before.yaml and after.yaml. Note that both these were run on top of https://reviews.llvm.org/D150997, which is yet to make it into the main branch.

[barannikov88]

Is SmallVector.h still required in Error.h?

[IncludeGuardian]

Fix compile issues

[IncludeGuardian]

@barannikov88 no it's not. I was going to commit separately to keep the change small, but it turns out that if I move this to the source file there are no additional changes needed. SmallVector.h has now been moved to Error.cpp as well.

[barannikov88]

In D153229#4444134, @IncludeGuardian wrote:

@barannikov88 no it's not. I was going to commit separately to keep the change small, but it turns out that if I move this to the source file there are no additional changes needed. SmallVector.h has now been moved to Error.cpp as well.

I guess it is transitively included from some other header, probably Twine.h.
LGTM with build fixed. I'll leave it for someone else to accept so that it does not disappear from review queue.

[IncludeGuardian]

Fix missing include

[IncludeGuardian]

Add back all includes (bad arc change)

[IncludeGuardian]

Fix missing includes for Windows-only files

[MaskRay]

Seems that the main change is in llvm/include/llvm/Support/Error.h. I think there is a small but not negligible chance that this patch may cause a breakage for some build configurations.
I suggest that you land the #include "llvm/ADT/StringExtras.h" addition part first, then land a much smaller change that modifes llvm/include/llvm/Support/Error.h. So that even if someone detects a failure and decides to revert it, the churn only goes to llvm/include/llvm/Support/Error.h

[IncludeGuardian]

@MaskRay good idea, I have split into 2 commits and pushed to the main

[MaskRay]

Glad that you landed the first change separately:) The Error.cpp change was reverted by b3c8554f28a95063e406924c25336e0da7efb4fd which was more focused.

[MaskRay]

I've used something like for i in llvm clang clang-tools flang lld lldb bolt mlir; do LIT_OPTS='--filter=xxx --allow-empty-runs' ninja -C /tmp/Rel check-$i to ensure I have built everything, beside a few projects I run check-$i.
It's always good to make the last-minute testing as llvm-project has 100+ commits every day.

llvm/include/llvm/Support/Error.h

 //===- llvm/Support/Error.h - Recoverable error handling --------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines an API used to report recoverable errors.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_ERROR_H
 #define LLVM_SUPPORT_ERROR_H
 
 #include "llvm-c/Error.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Config/abi-breaking.h"
 #include "llvm/Support/AlignOf.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/Format.h"

 ///
 /// This is useful in the base level of your program to allow clean termination
 /// (allowing clean deallocation of resources, etc.), while reporting error
 /// information to the user.
 void logAllUnhandledErrors(Error E, raw_ostream &OS, Twine ErrorBanner = {});
 
 /// Write all error messages (if any) in E to a string. The newline character
 /// is used to separate error messages.
-inline std::string toString(Error E) {
-  SmallVector<std::string, 2> Errors;
-  handleAllErrors(std::move(E), [&Errors](const ErrorInfoBase &EI) {
-    Errors.push_back(EI.message());
-  });
-  return join(Errors.begin(), Errors.end(), "\n");
-}
+std::string toString(Error E);
 
 /// Consume a Error without doing anything. This method should be used
 /// only where an error can be considered a reasonable and expected return
 /// value.
 ///
 /// Uses of this method are potentially indicative of design problems: If it's
 /// legitimate to do nothing while processing an "error", the error-producer
 /// might be more clearly refactored to return an std::optional<T>.

llvm/lib/Support/Error.cpp

 //===----- lib/Support/Error.cpp - Error and associated utilities ---------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/Error.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <system_error>
 
 using namespace llvm;
 
 namespace {
 
if (!E)
     return;
   OS << ErrorBanner;
   handleAllErrors(std::move(E), [&](const ErrorInfoBase &EI) {
     EI.log(OS);
     OS << "\n";
   });
 }
 
+/// Write all error messages (if any) in E to a string. The newline character
+/// is used to separate error messages.
+std::string toString(Error E) {
+  SmallVector<std::string, 2> Errors;
+  handleAllErrors(std::move(E), [&Errors](const ErrorInfoBase &EI) {
+    Errors.push_back(EI.message());
+  });
+  return join(Errors.begin(), Errors.end(), "\n");
+}
 
 std::error_code ErrorList::convertToErrorCode() const {
   return std::error_code(static_cast<int>(ErrorErrorCode::MultipleErrors),
                          getErrorErrorCat());
 }
 
 std::error_code inconvertibleErrorCode() {
   return std::error_code(static_cast<int>(ErrorErrorCode::InconvertibleError),