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https://gcc.gnu.org/PR86952
https://bugs.gentoo.org/682218
From 4fa11b10fc05a132b68b6df198706a97c3f4d61e Mon Sep 17 00:00:00 2001
From: marxin <marxin@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Mon, 11 Mar 2019 09:38:06 +0000
Subject: [PATCH] Backport r269492
2019-03-11 Martin Liska <mliska@suse.cz>
Backport from mainline
2019-03-08 Martin Liska <mliska@suse.cz>
PR target/86952
* config/i386/i386.c (ix86_option_override_internal): Disable
jump tables when retpolines are used.
2019-03-11 Martin Liska <mliska@suse.cz>
Backport from mainline
2019-03-08 Martin Liska <mliska@suse.cz>
PR target/86952
* gcc.target/i386/indirect-thunk-7.c: Use jump tables to match
scanned pattern.
* gcc.target/i386/indirect-thunk-inline-7.c: Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-8-branch@269572 138bc75d-0d04-0410-961f-82ee72b054a4
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -4958,6 +4958,12 @@ ix86_option_override_internal (bool main_args_p,
opts->x_param_values,
opts_set->x_param_values);
+ /* PR86952: jump table usage with retpolines is slow.
+ The PR provides some numbers about the slowness. */
+ if (ix86_indirect_branch != indirect_branch_keep
+ && !opts_set->x_flag_jump_tables)
+ opts->x_flag_jump_tables = 0;
+
return true;
}
--- a/gcc/testsuite/gcc.target/i386/indirect-thunk-7.c
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-7.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk -fno-pic" } */
+/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk -fno-pic -fjump-tables" } */
void func0 (void);
void func1 (void);
--- a/gcc/testsuite/gcc.target/i386/indirect-thunk-inline-7.c
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-inline-7.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk-inline -fno-pic" } */
+/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk-inline -fno-pic -fjump-tables" } */
void func0 (void);
void func1 (void);
--
2.21.0
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