[PATCH] [RFC] rs6000: -mreadonly-in-sdata (PR82411)

[Segher Boessenkool]

This adds a new option -mreadonly-in-sdata (on by default) that
controls whether readonly data can be put in sdata.  (For EABI this
does nothing, readonly data is put in sdata2 as usual).

Kees, could you try this out with your use case?  Add the flag
-mno-readonly-in-sdata in your build scripts.  The patch is against
GCC trunk.

[ I'll write documentation if this works; backports (to GCC 7 and
  GCC 6) can happen as well. ]


Segher


---
 gcc/config/rs6000/rs6000.c                     | 5 +++++
 gcc/config/rs6000/sysv4.opt                    | 4 ++++
 gcc/testsuite/gcc.target/powerpc/ppc-sdata-2.c | 1 +
 3 files changed, 10 insertions(+)

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index bd0a564..dbc1d79 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -32591,6 +32591,11 @@ rs6000_elf_in_small_data_p (const_tree decl)
     }
   else
     {
+      /* If we are told not to put readonly data in sdata, then don't.  */
+      if (TREE_READONLY (decl) && rs6000_sdata != SDATA_EABI
+	  && !rs6000_readonly_in_sdata)
+	return false;
+
       HOST_WIDE_INT size = int_size_in_bytes (TREE_TYPE (decl));
 
       if (size > 0
diff --git a/gcc/config/rs6000/sysv4.opt b/gcc/config/rs6000/sysv4.opt
index 9534c1c..fb03c0a 100644
--- a/gcc/config/rs6000/sysv4.opt
+++ b/gcc/config/rs6000/sysv4.opt
@@ -27,6 +27,10 @@ msdata=
 Target RejectNegative Joined Var(rs6000_sdata_name)
 Select method for sdata handling.
 
+mreadonly-in-sdata
+Target Report Var(rs6000_readonly_in_sdata) Init(1) Save
+Allow readonly data in sdata.
+
 mtls-size=
 Target RejectNegative Joined Var(rs6000_tls_size) Enum(rs6000_tls_size)
 Specify bit size of immediate TLS offsets.
diff --git a/gcc/testsuite/gcc.target/powerpc/ppc-sdata-2.c b/gcc/testsuite/gcc.target/powerpc/ppc-sdata-2.c
index 570c81f..ee77456 100644
--- a/gcc/testsuite/gcc.target/powerpc/ppc-sdata-2.c
+++ b/gcc/testsuite/gcc.target/powerpc/ppc-sdata-2.c
@@ -5,6 +5,7 @@
 /* { dg-final { scan-assembler-not "\\.section\[ \t\]\\.sdata2," } } */
 /* { dg-final { scan-assembler "sdat@sdarel\\(13\\)" } } */
 /* { dg-final { scan-assembler "sdat2@sdarel\\(13\\)" } } */
+/* { dg-skip-if "" { *-*-* } { "-mno-readonly-in-sdata" } { "" } } */
 
 
 int sdat = 2;
-- 
1.8.3.1