The -mcmodel=large option was originally added to handle generation of
large binaries with large PLTs. However, when compiling the Linux
kernel with allyesconfig the output binary is so large that the jump
instruction 26-bit immediate is not large enough to store the jump
offset to some symbols when linking. Example error:
relocation truncated to fit: R_OR1K_INSN_REL_26 against symbol `do_fpe_trap'
defined in .text section in arch/openrisc/kernel/traps.o
We fix this by forcing jump offsets to registers when -mcmodel=large.
Note, to get the Linux kernel allyesconfig config to work with OpenRISC,
this patch is needed along with some other patches to the Linux hand
coded assembly bits.
gcc/ChangeLog:
* config/or1k/predicates.md (call_insn_operand): Add condition
to not allow symbol_ref operands with TARGET_CMODEL_LARGE.
* config/or1k/or1k.opt: Document new -mcmodel=large
implications.
* doc/invoke.texi: Likewise.
---
If anyone is interested with the kernel patches I have them on this branch:
https://github.com/stffrdhrn/linux/commits/or1k-allyesconfig-2/
gcc/config/or1k/or1k.opt | 4 ++--
gcc/config/or1k/predicates.md | 3 ++-
gcc/doc/invoke.texi | 7 ++++---
3 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/gcc/config/or1k/or1k.opt b/gcc/config/or1k/or1k.opt
index 00c55603300..d252de08204 100644
--- a/gcc/config/or1k/or1k.opt
+++ b/gcc/config/or1k/or1k.opt
@@ -69,8 +69,8 @@ are used to perform unordered floating point compare and set
flag operations.
mcmodel=
Target RejectNegative Joined Enum(or1k_cmodel_type) Var(or1k_code_model)
Init(CMODEL_SMALL)
Specify the code model used for accessing memory addresses. Specifying large
-enables generating binaries with large global offset tables. By default the
-value is small.
+enables generating binaries with large global offset tables and calling
+functions anywhere in an executable. By default the value is small.
Enum
Name(or1k_cmodel_type) Type(enum or1k_cmodel_type)
diff --git a/gcc/config/or1k/predicates.md b/gcc/config/or1k/predicates.md
index 11bb5181436..144f4d7b577 100644
--- a/gcc/config/or1k/predicates.md
+++ b/gcc/config/or1k/predicates.md
@@ -61,7 +61,8 @@
(match_test "TARGET_ROR"))))
(define_predicate "call_insn_operand"
- (ior (match_code "symbol_ref")
+ (ior (and (match_code "symbol_ref")
+ (match_test "!TARGET_CMODEL_LARGE"))
(match_operand 0 "register_operand")))
(define_predicate "high_operand"
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index ab89686256d..cfbb9eda083 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -30879,12 +30879,13 @@ to store the immediate to a register first.
@opindex mcmodel=
@opindex mcmodel=small
@item -mcmodel=small
-Generate OpenRISC code for the small model: The GOT is limited to 64k. This is
-the default model.
+Generate OpenRISC code for the small model: The GOT is limited to 64k and
+function call jumps are limited to 64M offsets. This is the default model.
@opindex mcmodel=large
@item -mcmodel=large
-Generate OpenRISC code for the large model: The GOT may grow up to 4G in size.
+Generate OpenRISC code for the large model: The GOT may grow up to 4G in size
+and function call jumps can target the full 4G address space.
@end table
--
2.49.0
