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Re: [PATCH 5/6] [RS6000] Use standard call patterns for __tls_get_addr calls


On Tue, Nov 27, 2018 at 10:29:29AM -0600, Segher Boessenkool wrote:
> Hi!

Thanks for the review!

> > +(define_insn "*tls_gdld_aix<P:bits>"
> > +  [(match_parallel 3 ""
> 
> A match_parallel without predicate...  Does this work?!

Yes.  In fact, rs6000/predicates.md any_parallel_operand is useless
except as documentation.  The only thing it checks is that its operand
is a parallel, but that has already been checked.

>  Does this not
> accidentally pick up the wrong things?

No.  The purpose of the predicate is to match anything beyond the
vector of expressions.  So tls_gdld_aix* matches insns that look like:

     (set (match_operand:P 0 "gpc_reg_operand" "=b")
	  (call (mem:SI (match_operand:P 1))
		(match_operand:P 2 "unspec_tls")))
     (match_dup 2)
     ...

This is sufficiently different from other calls, by virtue of the
"(match_dup 2)".

Incidentally, I think tls_gdld_aix and tls_gdld_sysv could be merged
at the expense of complicating the length attribute expression.

> Do you think we should to deprecate -mtls-markers in GCC 9?

Support for the TLS marker relocs was added to binutils in 2009 (git
commit 727fc41e077), so yes, the option is not likely to be useful
nowadays.

> Please test with -mtls-markers, too, if you can, and test on AIX.

Presumably you mean -mno-tls-markers.  -mtls-markers is the default.

> Looks fine.  Thank you for the cleanup!  Okay for trunk, but please do the
> extra testing.

Huh, local testing of -mno-tls-markers showed a lack of a
TARGET_TLS_MARKERS check in rs6000_call_template_1.  Likely this would
blow up on AIX.  I'll test with the following delta.

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 56ca117a0a0..5f4fcee3b33 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -8622,7 +8622,7 @@ edit_tls_call_insn (rtx arg)
 }
 
 /* Passes the tls arg value for global dynamic and local dynamic
-   emit_library_call_value in rs6000_legitimize_Tls_address to
+   emit_library_call_value in rs6000_legitimize_tls_address to
    rs6000_call_aix and rs6000_call_sysv.  This is used to emit the
    marker relocs put on __tls_get_addr calls.  */
 static rtx global_tlsarg;
@@ -21429,7 +21429,7 @@ rs6000_call_template_1 (rtx *operands, unsigned int funop, bool sibcall)
 
   char arg[12];
   arg[0] = 0;
-  if (GET_CODE (operands[funop + 1]) == UNSPEC)
+  if (TARGET_TLS_MARKERS && GET_CODE (operands[funop + 1]) == UNSPEC)
     {
       if (XINT (operands[funop + 1], 1) == UNSPEC_TLSGD)
 	sprintf (arg, "(%%%u@tlsgd)", funop + 1);

-- 
Alan Modra
Australia Development Lab, IBM


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