GCN: Tag '-march=[...]', '-mtune=[...]' as 'Negative' of themselves [PR112669]

Certain other command-line flags are mutually exclusive (random example: GCN
'-march=gfx906', '-march=gfx908').  If they're not appropriately marked up,
this does disturb the multilib selection machinery, for example:

    $ build-gcc-offload-amdgcn-amdhsa/gcc/xgcc -print-multi-directory -march=gfx906
    gfx906
    $ build-gcc-offload-amdgcn-amdhsa/gcc/xgcc -print-multi-directory -march=gfx908
    gfx908
    $ build-gcc-offload-amdgcn-amdhsa/gcc/xgcc -print-multi-directory -march=gfx906 -march=gfx908
    .

In the last invocation, '-march=gfx900 -march=gfx906', for example, in
'gcc/gcc.cc:set_multilib_dir' we see both flags -- which there doesn't exist a
matching multilib for, therefore we "fail" to the default ('.').  Tagges as
'Negative', only the last flag survives, and we, for example, get the expected:

    $ build-gcc-offload-amdgcn-amdhsa/gcc/xgcc -print-multi-directory -march=gfx906 -march=gfx908
    gfx908

I quickly found that the same also applies to GCN's '-mtune=[...]', but I've
not otherwise reviewed the GCN options.

	PR target/112669
	gcc/
	* config/gcn/gcn.opt (march=, mtune=): Tag as 'Negative' of
	themselves.

diff --git a/gcc/config/gcn/gcn.opt b/gcc/config/gcn/gcn.opt
index 7a852c51c84c3246f87b8b4c39edc172f73caf03..e5db6df92d772a501c33fbc717df11a441dda064 100644 (file)
--- a/gcc/config/gcn/gcn.opt
+++ b/gcc/config/gcn/gcn.opt
@@ -44,11 +44,11 @@ EnumValue
 Enum(gpu_type) String(gfx1030) Value(PROCESSOR_GFX1030)
 
 march=
-Target RejectNegative Joined ToLower Enum(gpu_type) Var(gcn_arch) Init(PROCESSOR_FIJI)
+Target RejectNegative Negative(march=) Joined ToLower Enum(gpu_type) Var(gcn_arch) Init(PROCESSOR_FIJI)
 Specify the name of the target GPU.
 
 mtune=
-Target RejectNegative Joined ToLower Enum(gpu_type) Var(gcn_tune) Init(PROCESSOR_FIJI)
+Target RejectNegative Negative(mtune=) Joined ToLower Enum(gpu_type) Var(gcn_tune) Init(PROCESSOR_FIJI)
 Specify the name of the target GPU.
 
 m32