diff mbox series

[RFC,1/5] RISC-V: Add Zcmt table-jump relocation definitions

Message ID 20260627104555.331493-2-jiawei@iscas.ac.cn
State New
Headers
Series RISC-V: Add Zcmt table-jump relaxation support |

Commit Message

Jiawei June 27, 2026, 10:45 a.m. UTC 
  Add a ZCMT table jump relaxation pass in the linker, the ELF relocation
number, opcode constants, and RISC-V BFD parameter
state needed by linker table-jump relaxation.

bfd/ChangeLog:

	* elfxx-riscv.c: Add TABLE_JUMP howto.
	* elfxx-riscv.h (struct riscv_elf_params): Add relax_zcmt field.
	(enum riscv_relax_pass): New enum.
	(enum jvt_profiling_trip): Ditto.

include/ChangeLog:

	* elf/riscv.h (R_RISCV_TABLE_JUMP): New reloc number.
	(RISCV_TABLE_JUMP_BASE_SYMBOL): New symbol name.
	(TABLE_JUMP_SEC_NAME): New section name.
	* opcode/riscv.h (ZCMT_TOTAL_ENTRIES): New Zcmt constants.
	(ZCMT_JT_BEGIN): Ditto.
	(ZCMT_JT_END): Ditto.
	(ZCMT_JT_NUM_ENTRIES): Ditto.
	(ZCMT_JALT_BEGIN): Ditto.
	(ZCMT_JALT_END): Ditto.
	(ZCMT_JALT_NUM_ENTRIES): Ditto.
---
 bfd/elfxx-riscv.c      |  4 ++++
 bfd/elfxx-riscv.h      | 21 +++++++++++++++++++++
 include/elf/riscv.h    |  5 +++++
 include/opcode/riscv.h |  9 +++++++++
 4 files changed, 39 insertions(+)
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Patch

diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index 961c44a9206..615f644d336 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -961,6 +961,10 @@  static const reloc_howto_type howto_table_internal[] =
 	 0,				/* src_mask */
 	 ENCODE_STYPE_IMM (-1U),	/* dst_mask */
 	 false),			/* pcrel_offset */
+
+  /* R_RISCV_TABLE_JUMP is linker-internal.  It is consumed before final
+     relocations are emitted and must never become psABI-visible.  */
+  EMPTY_HOWTO (0),
 };
 
 /* A mapping from BFD reloc types to RISC-V ELF reloc types.  */
diff --git a/bfd/elfxx-riscv.h b/bfd/elfxx-riscv.h
index e57e90462f8..6adf1d6d0ca 100644
--- a/bfd/elfxx-riscv.h
+++ b/bfd/elfxx-riscv.h
@@ -44,6 +44,8 @@  struct riscv_elf_params
   bool relax_gp;
   /* Whether to check if SUB_ULEB128 relocation has non-zero addend.  */
   bool check_uleb128;
+  /* Whether to relax code sequences for Zcmt.  */
+  bool relax_zcmt;
 };
 
 extern void riscv_elf32_set_options (struct bfd_link_info *,
@@ -101,6 +103,25 @@  typedef struct
   bool check_unknown_prefixed_ext;
 } riscv_parse_subset_t;
 
+/* List the relaxation passes.  */
+enum riscv_relax_pass
+{
+  RELAX_PASS_SHORTEN_LUI_CALL_TRREL_PCREL,
+  RELAX_PASS_CAN_BE_DISABLED = RELAX_PASS_SHORTEN_LUI_CALL_TRREL_PCREL,
+  RELAX_PASS_TABLE_JUMP_PROFILING,
+  RELAX_PASS_ALIGNMENT,
+  RELAX_PASS_END,
+};
+
+/* Trips for jvt profiling relaxation pass.  */
+enum jvt_profiling_trip
+{
+  JVT_PROFILING_RECORD_SYM,
+  JVT_PROFILING_RANK,
+  JVT_PROFILING_DETERMINE,
+  JVT_PROFILING_TRIM,
+};
+
 extern bool
 riscv_parse_subset (riscv_parse_subset_t *,
 		    const char *);
diff --git a/include/elf/riscv.h b/include/elf/riscv.h
index f6ca3d4acd8..02a0184b7ee 100644
--- a/include/elf/riscv.h
+++ b/include/elf/riscv.h
@@ -105,6 +105,7 @@  END_RELOC_NUMBERS (R_RISCV_max)
 #define R_RISCV_GPREL_S           (R_RISCV_max + 4)
 #define R_RISCV_TPREL_I           (R_RISCV_max + 5)
 #define R_RISCV_TPREL_S           (R_RISCV_max + 6)
+#define R_RISCV_TABLE_JUMP        (R_RISCV_max + 7)
 
 /* Processor specific flags for the ELF header e_flags field.  */
 
@@ -132,6 +133,10 @@  END_RELOC_NUMBERS (R_RISCV_max)
 /* The name of the global pointer symbol.  */
 #define RISCV_GP_SYMBOL "__global_pointer$"
 
+#define RISCV_TABLE_JUMP_BASE_SYMBOL "__jvt_base$"
+
+#define TABLE_JUMP_SEC_NAME ".riscv.jvt"
+
 /* Processor specific dynamic array tags.  */
 #define DT_RISCV_VARIANT_CC (DT_LOPROC + 1)
 
diff --git a/include/opcode/riscv.h b/include/opcode/riscv.h
index b4587976ea2..5e1157e3e50 100644
--- a/include/opcode/riscv.h
+++ b/include/opcode/riscv.h
@@ -698,6 +698,15 @@  struct riscv_opcode
    disassembler, and requires special treatment by the assembler.  */
 #define INSN_MACRO		0xffffffff
 
+/* Define Zcmt jump table constants.  */
+#define ZCMT_TOTAL_ENTRIES 256
+#define ZCMT_JT_BEGIN 0
+#define ZCMT_JT_END 31
+#define ZCMT_JT_NUM_ENTRIES (ZCMT_JT_END - ZCMT_JT_BEGIN + 1)
+#define ZCMT_JALT_BEGIN (ZCMT_JT_END + 1)
+#define ZCMT_JALT_END (ZCMT_TOTAL_ENTRIES - 1)
+#define ZCMT_JALT_NUM_ENTRIES (ZCMT_JALT_END - ZCMT_JALT_BEGIN + 1)
+
 /* This is a list of macro expanded instructions.  */
 enum
 {