Re: Make '-frust-incomplete-and-experimental-compiler-do-not-use' a 'Common' option (was: Rust front-end patches v4)

[Thomas Schwinge <thomas@codesourcery.com>]

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Hi!

On 2022-12-15T08:53:13+0100, Richard Biener <richard.guenther@gmail.com> wrote:
> On Wed, Dec 14, 2022 at 11:58 PM Thomas Schwinge
> <thomas@codesourcery.com> wrote:
>> On 2022-12-13T14:40:36+0100, Arthur Cohen <arthur.cohen@embecosm.com> wrote:
>> > We've also added one more commit, which only affects files inside the
>> > Rust front-end folder. This commit adds an experimental flag, which
>> > blocks the compilation of Rust code when not used.
>>
>> (That's commit r13-4675-gb07ef39ffbf4e77a586605019c64e2e070915ac3
>> "gccrs: Add fatal_error when experimental flag is not present".)
>>
>> I noticed that GCC/Rust recently lost all LTO variants in torture
>> testing -- due to this commit.  :-O
>>
>> OK to push the attached
>> "Make '-frust-incomplete-and-experimental-compiler-do-not-use' a 'Common' option",
>> or should this be done differently?
>
> Just add 'LTO' to the option in lang.opt, like
>
> frust-incomplete-and-experimental-compiler-do-not-use
> Rust LTO Var(flag_rust_experimental)
> Enable experimental compilation of Rust files at your own risk

That doesn't work; it's 'cc1' that is complaining here.


Grüße
 Thomas


>> With that, we get back:
>>
>>      PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O0  (test for excess errors)
>>      PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O1  (test for excess errors)
>>      PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2  (test for excess errors)
>>     +PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fno-use-linker-plugin -flto-partition=none  (test for excess errors)
>>     +PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (test for excess errors)
>>      PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O3 -g  (test for excess errors)
>>      PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -Os  (test for excess errors)
>>
>> Etc., and in total:
>>
>>                     === rust Summary for unix ===
>>
>>     # of expected passes            [-4990-]{+6718+}
>>     # of expected failures          [-39-]{+51+}
>>
>>
>> Grüße
>>  Thomas
>>
>>
>> > We hope this helps
>> > indicate to users that the compiler is not yet ready, but can still be
>> > experimented with :)
>> >
>> > We plan on removing that flag as soon as possible, but in the meantime,
>> > we think it will help not creating divide within the Rust ecosystem, as
>> > well as not waste Rust crate maintainers' time.


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From 3b2a8a4df1637a0cad738165a2afa9b34e286fcf Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Wed, 14 Dec 2022 17:16:42 +0100
Subject: [PATCH] Make '-frust-incomplete-and-experimental-compiler-do-not-use'
 a 'Common' option

I noticed that GCC/Rust recently lost all LTO variants in torture testing:

     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O0  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O1  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2  (test for excess errors)
    -PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fno-use-linker-plugin -flto-partition=none  (test for excess errors)
    -PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O3 -g  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -Os  (test for excess errors)

Etc.

The reason is that when probing for availability of LTO, we run into:

    spawn [...]/build-gcc/gcc/testsuite/rust/../../gccrs -B[...]/build-gcc/gcc/testsuite/rust/../../ -fdiagnostics-plain-output -frust-incomplete-and-experimental-compiler-do-not-use -flto -c -o lto8274.o lto8274.c
    cc1: warning: command-line option '-frust-incomplete-and-experimental-compiler-do-not-use' is valid for Rust but not for C

For GCC/Rust testing, this flag is defaulted in
'gcc/testsuite/lib/rust.exp:rust_init':

    lappend ALWAYS_RUSTFLAGS "additional_flags=-frust-incomplete-and-experimental-compiler-do-not-use"

Make it generally accepted without "is valid for Rust but not for [...]"
diagnostic.

	gcc/rust/
	* lang.opt
	(-frust-incomplete-and-experimental-compiler-do-not-use): Remove.
	gcc/
	* common.opt
	(-frust-incomplete-and-experimental-compiler-do-not-use): New.
---
 gcc/common.opt    | 6 ++++++
 gcc/rust/lang.opt | 4 ----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/gcc/common.opt b/gcc/common.opt
index 562d73d7f552..eba28e650f94 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2552,6 +2552,12 @@ frounding-math
 Common Var(flag_rounding_math) Optimization SetByCombined
 Disable optimizations that assume default FP rounding behavior.
 
+; This option applies to Rust only, but is defined 'Common' here, so that it's
+; generally accepted without "is valid for Rust but not for [...]" diagnostic.
+frust-incomplete-and-experimental-compiler-do-not-use
+Common Var(flag_rust_experimental)
+Enable experimental compilation of Rust files at your own risk.
+
 fsched-interblock
 Common Var(flag_schedule_interblock) Init(1) Optimization
 Enable scheduling across basic blocks.
diff --git a/gcc/rust/lang.opt b/gcc/rust/lang.opt
index 63732a636a3d..6187fbf29352 100644
--- a/gcc/rust/lang.opt
+++ b/gcc/rust/lang.opt
@@ -66,10 +66,6 @@ frust-dump-
 Rust Joined RejectNegative
 -frust-dump-<type>	Dump Rust frontend internal information.
 
-frust-incomplete-and-experimental-compiler-do-not-use
-Rust Var(flag_rust_experimental)
-Enable experimental compilation of Rust files at your own risk
-
 frust-max-recursion-depth=
 Rust RejectNegative Type(int) Var(rust_max_recursion_depth) Init(64)
 -frust-max-recursion-depth=integer
-- 
2.35.1