tile: improve detection for missing -mcmodel=large support

The existing test avoided passing -mcmodel=large if the compiler didn't
support it.  However, we need to test not just the compiler support, but
also the toolchain (as and ld) support, so make the test more complete.
In addition, we have to avoid using the hwN_plt() assembly operators if
that support is missing, so guard the uses with #ifdef NO_PLT_PCREL.

This allows us to properly build glibc with the current community
binutils, which doesn't yet have the PC-relative PLT operator support.
The -mcmodel=large support is in gcc 4.8, but the toolchain support
won't be present in the community until binutils 2.24.

diff --git a/ports/ChangeLog.tile b/ports/ChangeLog.tile
index 7204ae578bc3d4ae030c65a14569a67216df6680..33ffa71fe66f2c2c5eebedd8eec140ae0ccdcd68 100644 (file)
--- a/ports/ChangeLog.tile
+++ b/ports/ChangeLog.tile
@@ -1,3 +1,12 @@
+2013-05-23  Chris Metcalf  <cmetcalf@tilera.com>
+
+       * sysdeps/tile/tilegx/Makefile ($(cflags-mcmodel-large)):
+       Test for assembler and linker support for "-mcmodel=large -fpic"
+       in addition to compiler support; provide -DNO_PLT_PCREL if not.
+       * sysdeps/tile/start.S [NO_PLT_PCREL]: Guard for no PC-relative
+       PLT operators in assembly.
+       * sysdeps/tile/crti.S [NO_PLT_PCREL]: Likewise.
+
 2013-05-22  Edjunior Barbosa Machado  <emachado@linux.vnet.ibm.com>
 
        * sysdeps/unix/sysv/linux/tile/bits/siginfo.h (siginfo_t): Fix comment

diff --git a/ports/sysdeps/tile/crti.S b/ports/sysdeps/tile/crti.S
index 9046010dc128af1388f2bb87e4e274cec71622ed..7e8e559b91e04fbc18516b15c001941a45928eec 100644 (file)
--- a/ports/sysdeps/tile/crti.S
+++ b/ports/sysdeps/tile/crti.S
@@ -95,7 +95,7 @@ _init:
        LD_PTR r0, r0
        BEQZ r0, .Lno_weak_fn
        jalr r0
-#elif defined(__tilegx__)
+#elif defined(__tilegx__) && !defined(NO_PLT_PCREL)
        /* Since we are calling from the start of the object to the PLT,
           call by loading the full address into a register.  */
        lnk r2

diff --git a/ports/sysdeps/tile/start.S b/ports/sysdeps/tile/start.S
index 99415647c20cb05c4ea5d8548a8fdd97b3dd97bb..3e7ec5cccf4d6050218b8ceed6ed1a5f1d610013 100644 (file)
--- a/ports/sysdeps/tile/start.S
+++ b/ports/sysdeps/tile/start.S
@@ -62,6 +62,13 @@
 #include <sysdep.h>
 #include <arch/abi.h>
 
+/* Just create no-ops if we don't support PC-relative PLT relocations. */
+#ifdef NO_PLT_PCREL
+# define hw2_last_plt(x)       0
+# define hw1_plt(x)            0
+# define hw0_plt(x)            0
+#endif
+
        .text
        .global _start
        .type   _start,@function
@@ -155,7 +162,11 @@ _start:
        }
        {
         ADD_PTR r4, r4, r13
-        jalr r12
+# ifdef NO_PLT_PCREL
+        j plt(__libc_start_main)
+# else
+        jr r12
+# endif
        }
 #else
         addli r0, r13, lo16(main - .Lmy_pc)

diff --git a/ports/sysdeps/tile/tilegx/Makefile b/ports/sysdeps/tile/tilegx/Makefile
index d3a0e970a77e115bfc6d0eab7cf1420dfd3cd738..4281dd98fc7ca62e8991c515f1c6948d0ce6cf13 100644 (file)
--- a/ports/sysdeps/tile/tilegx/Makefile
+++ b/ports/sysdeps/tile/tilegx/Makefile
@@ -1,12 +1,16 @@
 include $(common-objpfx)cflags-mcmodel-large.mk
 
+# Check for gcc to support the command-line switch, and for
+# binutils to support the hwN_plt() assembly operators and relocations.
 $(common-objpfx)cflags-mcmodel-large.mk: $(common-objpfx)config.make
        mcmodel=no; \
-       $(CC) -S -o /dev/null -xc /dev/null -mcmodel=large && mcmodel=yes; \
+       (echo 'int main() { return getuid(); }' | \
+        $(CC) -o /dev/null -xc - -mcmodel=large -fpic) && mcmodel=yes; \
        echo "cflags-mcmodel-large = $$mcmodel" > $@
 
-ifeq ($(subdir),csu)
 ifeq (yes,$(cflags-mcmodel-large))
+
+ifeq ($(subdir),csu)
 # elf-init.c is in libc_nonshared.o (the end of the shared object) but
 # must reach the _init symbol at the very start of the shared object.
 CFLAGS-elf-init.c += -mcmodel=large
@@ -15,4 +19,17 @@ CFLAGS-elf-init.c += -mcmodel=large
 # with profiling, but calls to libc.so via the PLT at the very end.
 CFLAGS-gmon-start.c += -mcmodel=large
 endif
+
+else
+
+# Don't try to compile assembly code with hwN_plt() directives if the
+# toolchain doesn't support -mcmodel=large.
+ifeq ($(subdir),csu)
+CPPFLAGS-start.S += -DNO_PLT_PCREL
+CPPFLAGS-crti.S += -DNO_PLT_PCREL
+endif
+ifeq ($(subdir),nptl)
+CPPFLAGS-pt-crti.S += -DNO_PLT_PCREL
+endif
+
 endif