https://bugs.gentoo.org/695420
https://gcc.gnu.org/PR69471#c13

From 537fd9d4dcaed8dae6248ec22a50603a591a3752 Mon Sep 17 00:00:00 2001
From: ktkachov <ktkachov@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 26 Sep 2019 10:52:42 +0000
Subject: [PATCH] driver: Also prune joined switches with negation

When -march=native is passed to host_detect_local_cpu to the backend,
it overrides all command lines after it.  That means

$ gcc -march=native -march=armv8-a

is treated as

$ gcc -march=armv8-a -march=native

Prune joined switches with Negative and RejectNegative to allow
-march=armv8-a to override previous -march=native on command-line.

This is the same fix as was applied for i386 in SVN revision 269164 but for
aarch64 and arm.

2019-09-26  Matt Turner  <mattst88@gmail.com>

	PR driver/69471
	* config/aarch64/aarch64.opt (march=): Add Negative(march=).
	(mtune=): Add Negative(mtune=).
	(mcpu=): Add Negative(mcpu=).
	* config/arm/arm.opt: Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@276148 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/config/aarch64/aarch64.opt | 6 +++---
 gcc/config/arm/arm.opt         | 6 +++---

--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -119,15 +119,15 @@ EnumValue
 Enum(aarch64_tls_size) String(48) Value(48)
 
 march=
-Target RejectNegative ToLower Joined Var(aarch64_arch_string)
+Target RejectNegative Negative(march=) ToLower Joined Var(aarch64_arch_string)
 Use features of architecture ARCH.
 
 mcpu=
-Target RejectNegative ToLower Joined Var(aarch64_cpu_string)
+Target RejectNegative Negative(mcpu=) ToLower Joined Var(aarch64_cpu_string)
 Use features of and optimize for CPU.
 
 mtune=
-Target RejectNegative ToLower Joined Var(aarch64_tune_string)
+Target RejectNegative Negative(mtune=) ToLower Joined Var(aarch64_tune_string)
 Optimize for CPU.
 
 mabi=
--- a/gcc/config/arm/arm.opt
+++ b/gcc/config/arm/arm.opt
@@ -82,7 +82,7 @@ mapcs-stack-check
 Target Report Mask(APCS_STACK) Undocumented
 
 march=
-Target RejectNegative ToLower Joined Var(arm_arch_string)
+Target RejectNegative Negative(march=) ToLower Joined Var(arm_arch_string)
 Specify the name of the target architecture.
 
 ; Other arm_arch values are loaded from arm-tables.opt
@@ -107,7 +107,7 @@ Target Report Mask(CALLER_INTERWORKING)
 Thumb: Assume function pointers may go to non-Thumb aware code.
 
 mcpu=
-Target RejectNegative ToLower Joined Var(arm_cpu_string)
+Target RejectNegative Negative(mcpu=) ToLower Joined Var(arm_cpu_string)
 Specify the name of the target CPU.
 
 mfloat-abi=
@@ -232,7 +232,7 @@ Target Report Mask(TPCS_LEAF_FRAME)
 Thumb: Generate (leaf) stack frames even if not needed.
 
 mtune=
-Target RejectNegative ToLower Joined Var(arm_tune_string)
+Target RejectNegative Negative(mtune=) ToLower Joined Var(arm_tune_string)
 Tune code for the given processor.
 
 mprint-tune-info
-- 
2.23.0