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authorNick Clifton <nickc@redhat.com>2008-05-21 08:09:38 +0000
committerNick Clifton <nickc@redhat.com>2008-05-21 08:09:38 +0000
commit726150b77a9c761f7b7ab7e342ea78c241f03c95 (patch)
tree355249aa6809c48961ef8767d26fc81bb2e0ce87
parent3ce6fddb771a3c25ec8b7bfac40d85d52bd917ab (diff)
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* ld.texinfo (ARM): Document --stub-group-size=N option.
Move description of --pic-veneer option into the ARM section. * NEWS: Mention the support for long function calls.
-rw-r--r--ld/ChangeLog7
-rw-r--r--ld/NEWS4
-rw-r--r--ld/ld.texinfo43
3 files changed, 46 insertions, 8 deletions
diff --git a/ld/ChangeLog b/ld/ChangeLog
index f43f5de..b1c57f1 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,10 @@
+2008-05-21 Christophe Lyon <christophe.lyon@st.com>
+ Nick Clifton <nickc@redhat.com>
+
+ * ld.texinfo (ARM): Document --stub-group-size=N option.
+ Move description of --pic-veneer option into the ARM section.
+ * NEWS: Mention the support for long function calls.
+
2008-05-15 Christophe Lyon <christophe.lyon@st.com>
* emultempl/armelf.em (build_section_lists): New function.
diff --git a/ld/NEWS b/ld/NEWS
index 637fd40..f28d514 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -1,4 +1,8 @@
-*- text -*-
+* The ARM ELF linker will now generate stubs for function calls to symbols that
+ are too far away. The placement of the stubs is controlled by a new linker
+ command line option: --stub-group-size=N.
+
Changes in 2.18:
* Linker sources now released under version 3 of the GNU General Public
diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index f5fc431..72d7a2a 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -5505,13 +5505,6 @@ trampoline address instead of the function address. This is typically the
case when a pointer to a function is taken. The pointer will in fact
point to the function trampoline.
-@cindex PIC_VENEER
-@kindex --pic-veneer
-The @samp{--pic-veneer} switch makes the linker use PIC sequences for
-ARM/Thumb interworking veneers, even if the rest of the binary
-is not PIC. This avoids problems on uClinux targets where
-@samp{--emit-relocs} is used to generate relocatable binaries.
-
@ifclear GENERIC
@lowersections
@end ifclear
@@ -5642,13 +5635,47 @@ are sufficient to avoid the erratum in both the scalar and vector cases.
@cindex NO_ENUM_SIZE_WARNING
@kindex --no-enum-size-warning
-The @samp{--no-enum-size-warning} switch prevents the linker from
+The @option{--no-enum-size-warning} switch prevents the linker from
warning when linking object files that specify incompatible EABI
enumeration size attributes. For example, with this switch enabled,
linking of an object file using 32-bit enumeration values with another
using enumeration values fitted into the smallest possible space will
not be diagnosed.
+@cindex PIC_VENEER
+@kindex --pic-veneer
+The @samp{--pic-veneer} switch makes the linker use PIC sequences for
+ARM/Thumb interworking veneers, even if the rest of the binary
+is not PIC. This avoids problems on uClinux targets where
+@samp{--emit-relocs} is used to generate relocatable binaries.
+
+@cindex STUB_GROUP_SIZE
+@kindex --stub-group-size=@var{N}
+The linker will automatically generate and insert small sequences of
+code into a linked ARM ELF executable whenever an attempt is made to
+perform a function call to a symbol that is too far away. The
+placement of these sequences of instructions - called stubs - is
+controlled by the command line option @option{--stub-group-size=N}.
+The placement is important because a poor choice can create a need for
+duplicate stubs, increasing the code sizw. The linker will try to
+group stubs together in order to reduce interruptions to the flow of
+code, but it needs guidance as to how big these groups should be and
+where they should be placed.
+
+The value of @samp{N}, the parameter to the
+@option{--stub-group-size=} option controls where the stub groups are
+placed. If it is negative then all stubs are placed before the first
+branch that needs them. If it is positive then the stubs can be
+placed either before or after the branches that need them. If the
+value of @samp{N} is 1 (either +1 or -1) then the linker will choose
+exactly where to place groups of stubs, using its built in heuristics.
+A value of @samp{N} greater than 1 (or smaller than -1) tells the
+linker that a single group of stubs can service at most @samp{N} bytes
+from the input sections.
+
+The default, if @option{--stub-group-size=} is not specified, is
+@samp{N = +1}.
+
@ifclear GENERIC
@lowersections
@end ifclear