[PATCH] [RISC-V] Fix the valid gp range for gp relax.

[Die Li <lidie@eswincomputing.com>]

Taking alignment into consideration, the conservative addressing range
for gp relax is [gp - 12bit_imm + max_alignment, gp + 12bit_imm - max_alignment],
which is smaller than the ideal GP addressing range [gp - 12bit_imm, gp + 
12bit_imm]. Therefore, when symval < gp, it is necessary to ensure that both 
symval and symval + reserve_size fall within the range [gp - 12bit_imm + alignment, 
gp + 12bit_imm - alignment]. Current linker takes the range of gp conservatively, 
this patch allows more symbols to be accessed by gp relative addressing.

Take the file named with gp-relax.s from this patch as the source file.

After assembling and linking with --relax option,
Before this patch:
0+[0-9a-f]+ <_start>:
.*:[ 	]+[0-9a-f]+[ 	]+lui+.*
.*:[ 	]+[0-9a-f]+[ 	]+addi+.*
.*:[ 	]+[0-9a-f]+[ 	]+lui+.*
.*:[ 	]+[0-9a-f]+[ 	]+addi+.*
.*:[ 	]+[0-9a-f]+[ 	]+auipc+.*
.*:[ 	]+[0-9a-f]+[ 	]+lw+.*

Check the symbal table after linking, we have :
Symbol table '.symtab' contains 19 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
...
     7: 0000000000011900     0 NOTYPE  GLOBAL DEFAULT  ABS __global_pointer$
...
    18: 0000000000011108  3600 OBJECT  GLOBAL DEFAULT    3 global_array

By comparing the values of `global_array` and `__global_pointer$`, the symbol of
global_array can be accessed by gp relative addressing.

After this patch:
0+[0-9a-f]+ <_start>:
.*:[ 	]+[0-9a-f]+[ 	]+addi[ 	]+a3,gp,\-[0-9]+ # [0-9a-f]+ <global_array>
.*:[ 	]+[0-9a-f]+[ 	]+addi[ 	]+a4,gp,\-[0-9]+ # [0-9a-f]+ <global_array+.*
.*:[ 	]+[0-9a-f]+[ 	]+lw[ 	]+a0,\-[0-9]+\(gp\) # [0-9a-f]+ <global_array>

Co-Authored by: Fei Gao <gaofei@eswincomputing.com>
Signed-off-by: Die Li <lidie@eswincomputing.com>

ChangeLog:

        * bfd/elfnn-riscv.c (_bfd_riscv_relax_lui): Fix the valid gp range.
        (_bfd_riscv_relax_pc): Likewise.
        * ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp: New test.
        * ld/testsuite/ld-riscv-elf/gp-relax.d: New test.
        * ld/testsuite/ld-riscv-elf/gp-relax.s: New test.
---
 bfd/elfnn-riscv.c                          |  6 +++--
 ld/testsuite/ld-riscv-elf/gp-relax.d       | 14 ++++++++++
 ld/testsuite/ld-riscv-elf/gp-relax.s       | 30 ++++++++++++++++++++++
 ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp |  1 +
 4 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 ld/testsuite/ld-riscv-elf/gp-relax.d
 create mode 100644 ld/testsuite/ld-riscv-elf/gp-relax.s

diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index 09aa7be225e..00e692c6924 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -4633,7 +4633,8 @@ _bfd_riscv_relax_lui (bfd *abfd,
       || (symval >= gp
 	  && VALID_ITYPE_IMM (symval - gp + max_alignment + reserve_size))
       || (symval < gp
-	  && VALID_ITYPE_IMM (symval - gp - max_alignment - reserve_size)))
+          && VALID_ITYPE_IMM (symval - gp - max_alignment)
+          && VALID_ITYPE_IMM (symval - gp + max_alignment + reserve_size)))
     {
       unsigned sym = ELFNN_R_SYM (rel->r_info);
       switch (ELFNN_R_TYPE (rel->r_info))
@@ -4897,7 +4898,8 @@ _bfd_riscv_relax_pc (bfd *abfd ATTRIBUTE_UNUSED,
       || (symval >= gp
 	  && VALID_ITYPE_IMM (symval - gp + max_alignment + reserve_size))
       || (symval < gp
-	  && VALID_ITYPE_IMM (symval - gp - max_alignment - reserve_size)))
+          && VALID_ITYPE_IMM (symval - gp - max_alignment)
+          && VALID_ITYPE_IMM (symval - gp + max_alignment + reserve_size)))
     {
       unsigned sym = hi_reloc.hi_sym;
       switch (ELFNN_R_TYPE (rel->r_info))
diff --git a/ld/testsuite/ld-riscv-elf/gp-relax.d b/ld/testsuite/ld-riscv-elf/gp-relax.d
new file mode 100644
index 00000000000..fa93c05ee2c
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/gp-relax.d
@@ -0,0 +1,14 @@
+#source: gp-relax.s
+#as:
+#ld: --relax
+#objdump: -d -Mno-aliases
+
+.*:[ 	]+file format .*
+
+
+Disassembly of section \.text:
+
+0+[0-9a-f]+ <_start>:
+.*:[ 	]+[0-9a-f]+[ 	]+addi[ 	]+a3,gp,\-[0-9]+ # [0-9a-f]+ <global_array>
+.*:[ 	]+[0-9a-f]+[ 	]+addi[ 	]+a4,gp,\-[0-9]+ # [0-9a-f]+ <global_array+.*
+.*:[ 	]+[0-9a-f]+[ 	]+lw[ 	]+a0,\-[0-9]+\(gp\) # [0-9a-f]+ <global_array>
diff --git a/ld/testsuite/ld-riscv-elf/gp-relax.s b/ld/testsuite/ld-riscv-elf/gp-relax.s
new file mode 100644
index 00000000000..36addbc770c
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/gp-relax.s
@@ -0,0 +1,30 @@
+	.globl	global_var
+	.section	.sbss,"aw",@nobits
+	.align	2
+	.type	global_var, @object
+	.size	global_var, 4
+global_var:
+	.zero	4
+
+	.globl	global_array
+	.bss
+	.align	3
+	.type	global_array, @object
+	.size	global_array, 3600
+global_array:
+	.zero	3600
+
+	.text
+	.align	1
+	.globl	_start
+	.type	_start, @function
+_start:
+	lui	a3,%hi(global_array)
+	addi	a3,a3,%lo(global_array)
+
+	lui	a4,%hi(global_array + 0x600)
+	addi	a4,a4,%lo(global_array + 0x600)
+
+.LA0:
+        auipc	a5,%pcrel_hi(global_array)
+	lw	a0,%pcrel_lo(.LA0)(a5)
diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
index 947a266ba72..6a04955b23b 100644
--- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
+++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
@@ -124,6 +124,7 @@ if [istarget "riscv*-*-*"] {
     run_dump_test "pcgp-relax-01"
     run_dump_test "pcgp-relax-01-norelaxgp"
     run_dump_test "pcgp-relax-02"
+    run_dump_test "gp-relax"
     run_dump_test "c-lui"
     run_dump_test "c-lui-2"
     run_dump_test "disas-jalr"
-- 
2.17.1