Re: [AArch64][TLSLE][1/3] Add the option "-mtls-size" for AArch64

[Jiong Wang <jiong dot wang at arm dot com>]

Marcus Shawcroft writes:

> On 19 August 2015 at 15:26, Jiong Wang <jiong.wang@arm.com> wrote:
>
>> 2015-08-19  Jiong Wang  <jiong.wang@arm.com>
>>
>> gcc/
>>   * config/aarch64/aarch64.opt (mtls-size): New entry.
>>   * config/aarch64/aarch64.c (initialize_aarch64_tls_size): New function.
>>   (aarch64_override_options_internal): Call initialize_aarch64_tls_size.
>>   * doc/invoke.texi (AArch64 Options): Document -mtls-size.
>>
>> --
>> Regards,
>> Jiong
>>
>
> +    case AARCH64_CMODEL_TINY:
> +      /* The maximum TLS size allowed under tiny is 1M.  */
> +      if (aarch64_tls_size > 20)
> + aarch64_tls_size = 20;
>
> The only valid values of aarch64_tls_size handled/expected by the
> remainder of the patch set is 12,24,32,48 so setting the value to 20
> here doesn;t make sense.

Thanks for pointing this out, how about the new patch attached?

2015-08-25  Jiong Wang  <jiong.wang@arm.com>

gcc/
  * config/aarch64/aarch64.opt (mtls-size): New entry.
  * config/aarch64/aarch64.c (initialize_aarch64_tls_size): New function.
  (aarch64_override_options_internal): Call initialize_aarch64_tls_size.
  * doc/invoke.texi (AArch64 Options): Document -mtls-size.

commit 36736a1a2133ffc949d3e00efdced8ef2c53cddd
Author: Jiong Wang <jiong.wang@arm.com>
Date:   Tue Aug 25 11:13:44 2015 +0100

    1

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 382be2c..318b852 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -7492,6 +7492,40 @@ aarch64_parse_one_override_token (const char* token,
   return;
 }
 
+/* A checking mechanism for the implementation of the tls size.  */
+
+static void
+initialize_aarch64_tls_size (struct gcc_options *opts)
+{
+  if (aarch64_tls_size == 0)
+    aarch64_tls_size = 24;
+
+  switch (opts->x_aarch64_cmodel_var)
+    {
+    case AARCH64_CMODEL_TINY:
+      /* Both the default and maximum TLS size allowed under tiny is 1M which
+	 needs two instructions to address, so we clamp the size to 24.  */
+      if (aarch64_tls_size > 24)
+	aarch64_tls_size = 24;
+      break;
+    case AARCH64_CMODEL_SMALL:
+      /* The maximum TLS size allowed under small is 4G.  */
+      if (aarch64_tls_size > 32)
+	aarch64_tls_size = 32;
+      break;
+    case AARCH64_CMODEL_LARGE:
+      /* The maximum TLS size allowed under large is 16E.
+	 FIXME: 16E should be 64bit, we only support 48bit offset now.  */
+      if (aarch64_tls_size > 48)
+	aarch64_tls_size = 48;
+      break;
+    default:
+      gcc_unreachable ();
+    }
+
+  return;
+}
+
 /* Parse STRING looking for options in the format:
      string	:: option:string
      option	:: name=substring
@@ -7584,6 +7618,7 @@ aarch64_override_options_internal (struct gcc_options *opts)
     }
 
   initialize_aarch64_code_model (opts);
+  initialize_aarch64_tls_size (opts);
 
   aarch64_override_options_after_change_1 (opts);
 }
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index 37c2c50..8642bdb 100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -96,6 +96,25 @@ mtls-dialect=
 Target RejectNegative Joined Enum(tls_type) Var(aarch64_tls_dialect) Init(TLS_DESCRIPTORS) Save
 Specify TLS dialect
 
+mtls-size=
+Target RejectNegative Joined Var(aarch64_tls_size) Enum(aarch64_tls_size)
+Specifies bit size of immediate TLS offsets.  Valid values are 12, 24, 32, 48.
+
+Enum
+Name(aarch64_tls_size) Type(int)
+
+EnumValue
+Enum(aarch64_tls_size) String(12) Value(12)
+
+EnumValue
+Enum(aarch64_tls_size) String(24) Value(24)
+
+EnumValue
+Enum(aarch64_tls_size) String(32) Value(32)
+
+EnumValue
+Enum(aarch64_tls_size) String(48) Value(48)
+
 march=
 Target RejectNegative ToLower Joined Var(aarch64_arch_string)
 -march=ARCH	Use features of architecture ARCH
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 27be317..f990bef 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -514,6 +514,7 @@ Objective-C and Objective-C++ Dialects}.
 -mstrict-align @gol
 -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer @gol
 -mtls-dialect=desc  -mtls-dialect=traditional @gol
+-mtls-size=@var{size} @gol
 -mfix-cortex-a53-835769  -mno-fix-cortex-a53-835769 @gol
 -mfix-cortex-a53-843419  -mno-fix-cortex-a53-843419 @gol
 -march=@var{name}  -mcpu=@var{name}  -mtune=@var{name}}
@@ -12409,6 +12410,11 @@ of TLS variables.  This is the default.
 Use traditional TLS as the thread-local storage mechanism for dynamic accesses
 of TLS variables.
 
+@item -mtls-size=@var{size}
+@opindex mtls-size
+Specify bit size of immediate TLS offsets.  Valid values are 12, 24, 32, 48.
+This option depends on binutils higher than 2.25.
+
 @item -mfix-cortex-a53-835769
 @itemx -mno-fix-cortex-a53-835769
 @opindex mfix-cortex-a53-835769