Re: [PATCH 2/2] configure: Check -falign-jumps=1 -falign-functions=1 beside -falign-loops=1

[Fangrui Song <maskray@google.com>]

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On 2021-08-25, Daniel Kiper wrote:
>On Mon, Aug 23, 2021 at 11:18:38PM -0700, Fangrui Song wrote:
>> Clang does not support -falign-jumps and only recently gained support
>> for -falign-loops. Test all the alignment options to avoid passing
>> unrecognized options to Clang:
>>
>>     clang-14: error: optimization flag '-falign-jumps=1' is not supported [-Werror,-Wignored-optimization-argument]
>>
>> When compiled with older Clang, the alignment options are not added, so
>> just avoid the complexity for each option.
>>
>> Signed-off-by: Fangrui Song <maskray@google.com>
>> ---
>>  configure.ac | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/configure.ac b/configure.ac
>> index 9a12151bd..8625e6776 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -798,8 +798,9 @@ fi
>>
>>  # Force no alignment to save space on i386.
>>  if test "x$target_cpu" = xi386; then
>> -  AC_CACHE_CHECK([whether -falign-loops works], [grub_cv_cc_falign_loop], [
>> -    CFLAGS="$TARGET_CFLAGS -falign-loops=1 -Werror"
>> +  AC_CACHE_CHECK([whether -falign-jumps=1 -falign-loops=1 -falign-functions=1 works],
>> +    [grub_cv_cc_falign_loop], [
>> +    CFLAGS="$TARGET_CFLAGS -falign-jumps=1 -falign-loops=1 -falign-functions=1 -Werror"
>
>I would prefer if you add a separate check for every -falign-* option.
>
>Daniel

The attached patch checks both -falign-jumps=1 and -falign-loops=1

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From fbef8198d26babeb402b480d333a4a5212069afb Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Wed, 25 Aug 2021 09:28:46 -0700
Subject: [PATCH] configure: Check -falign-jumps=1 beside -falign-loops=1

Clang does not support -falign-jumps and only recently gained support
for -falign-loops. -falign-jumps=1 should be tested beside
-fliang-loops=1 to avoid passing unrecognized options to Clang:

    clang-14: error: optimization flag '-falign-jumps=1' is not supported [-Werror,-Wignored-optimization-argument]

-falign-functions=1 is supported by GCC 5.1.0/Clang 3.8.0, so just add
the option unconditionally.

Signed-off-by: Fangrui Song <maskray@google.com>
---
 configure.ac | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 9a12151bd..91a6ef128 100644
--- a/configure.ac
+++ b/configure.ac
@@ -798,6 +798,8 @@ fi
 
 # Force no alignment to save space on i386.
 if test "x$target_cpu" = xi386; then
+  TARGET_CFLAGS="$TARGET_CFLAGS -falign-functions=1"
+
   AC_CACHE_CHECK([whether -falign-loops works], [grub_cv_cc_falign_loop], [
     CFLAGS="$TARGET_CFLAGS -falign-loops=1 -Werror"
     AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[]])],
@@ -806,7 +808,18 @@ if test "x$target_cpu" = xi386; then
   ])
 
   if test "x$grub_cv_cc_falign_loop" = xyes; then
-    TARGET_CFLAGS="$TARGET_CFLAGS -falign-jumps=1 -falign-loops=1 -falign-functions=1"
+    TARGET_CFLAGS="$TARGET_CFLAGS -falign-loops=1"
+  fi
+
+  AC_CACHE_CHECK([whether -falign-jumps works], [grub_cv_cc_falign_jumps], [
+    CFLAGS="$TARGET_CFLAGS -falign-jumps=1 -Werror"
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[]])],
+        [grub_cv_cc_falign_jumps=yes],
+	[grub_cv_cc_falign_jumps=no])
+  ])
+
+  if test "x$grub_cv_cc_falign_jumps" = xyes; then
+    TARGET_CFLAGS="$TARGET_CFLAGS -falign-jumps=1"
   fi
 fi
 
-- 
2.33.0.rc2.250.ged5fa647cd-goog