[PATCH] nvptx: bump default to PTX 4.1

[Andrew Stubbs]

On 20/12/2021 15:58, Andrew Stubbs wrote:
In order to support the %dynamic_smem_size PTX feature is is necessary 
to bump the minimum supported PTX version from 3.1 (~2013) to 4.1 (~2014).

Tobias has pointed out, privately, that the default version is both 
documented and encoded in the -mptx option, so I need to fix that too.

This patch adds -mptx=4.1, sets it as the default, and updates the 
documentation accordingly.

The -mptx=3.1 option is kept for backwards compatibility as an alias for 
4.1. There's no point in actually allowing 3.1 as any program linked 
against libgomp will fail (and that's all offloading programs).

OK for stage 1?

Andrew
nvptx: bump default to PTX 4.1

gcc/ChangeLog:

        * config/nvptx/nvptx-opts.h (ptx_version): Change PTX_VERSION_3_1 to
        PTX_VERSION_4_1.
        * config/nvptx/nvptx.c (nvptx_file_start): Bump minimum PTX version
        to 4.1.
        * config/nvptx/nvptx.opt (ptx_version): Add 4.1. Change default.
        doc/invoke.texi: -mptx default is now 4.1.

diff --git a/gcc/config/nvptx/nvptx-opts.h b/gcc/config/nvptx/nvptx-opts.h
index 7b6ecd42fed..c7fcf1c8cd4 100644
--- a/gcc/config/nvptx/nvptx-opts.h
+++ b/gcc/config/nvptx/nvptx-opts.h
@@ -31,7 +31,7 @@ enum ptx_isa
 
 enum ptx_version
 {
-  PTX_VERSION_3_1,
+  PTX_VERSION_4_1,
   PTX_VERSION_6_3,
   PTX_VERSION_7_0
 };
diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c
index ff44d9fdbef..9bc26d7de0c 100644
--- a/gcc/config/nvptx/nvptx.c
+++ b/gcc/config/nvptx/nvptx.c
@@ -5409,7 +5409,7 @@ nvptx_file_start (void)
   else if (TARGET_PTX_6_3)
     fputs ("\t.version\t6.3\n", asm_out_file);
   else
-    fputs ("\t.version\t3.1\n", asm_out_file);
+    fputs ("\t.version\t4.1\n", asm_out_file);
   if (TARGET_SM80)
     fputs ("\t.target\tsm_80\n", asm_out_file);
   else if (TARGET_SM75)
diff --git a/gcc/config/nvptx/nvptx.opt b/gcc/config/nvptx/nvptx.opt
index 1d88ef18d04..9e6a6a7fbff 100644
--- a/gcc/config/nvptx/nvptx.opt
+++ b/gcc/config/nvptx/nvptx.opt
@@ -79,8 +79,12 @@ Enum
 Name(ptx_version) Type(int)
 Known PTX versions (for use with the -mptx= option):
 
+; Keep 3.1 for backwards compatibility only
 EnumValue
-Enum(ptx_version) String(3.1) Value(PTX_VERSION_3_1)
+Enum(ptx_version) String(3.1) Value(PTX_VERSION_4_1)
+
+EnumValue
+Enum(ptx_version) String(4.1) Value(PTX_VERSION_4_1)
 
 EnumValue
 Enum(ptx_version) String(6.3) Value(PTX_VERSION_6_3)
@@ -89,5 +93,5 @@ EnumValue
 Enum(ptx_version) String(7.0) Value(PTX_VERSION_7_0)
 
 mptx=
-Target RejectNegative ToLower Joined Enum(ptx_version) Var(ptx_version_option) 
Init(PTX_VERSION_3_1)
+Target RejectNegative ToLower Joined Enum(ptx_version) Var(ptx_version_option) 
Init(PTX_VERSION_4_1)
 Specify the version of the ptx version to use.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 37836a7d614..92f0da62a2b 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -27056,8 +27056,8 @@ strings must be lower-case.  Valid ISA strings include 
@samp{sm_30} and
 @item -mptx=@var{version-string}
 @opindex mptx
 Generate code for given the specified PTX version (e.g.@: @samp{6.3}).
-Valid version strings include @samp{3.1} and @samp{6.3}.  The default PTX
-version is 3.1.
+Valid version strings include @samp{4.1} and @samp{6.3}.  The default PTX
+version is 4.1.
 
 @item -mmainkernel
 @opindex mmainkernel