[PATCH] RISC-V: Optimize relax of GP with max_alignment.

[lifang_xia@linux.alibaba.com]

From: Lifang Xia <lifang_xia@linux.alibaba.com>

The max_alignment defined out of [gp-2K, gp+2k), the max_alignment
shouldn't affect the relax of gp.
If the symbol is in [gp-2K, gp+2k), the max_alignment would be
replaced with the max_alignment of the section in [gp-2k, gp+2k).

bfd/
	* elfnn-riscv.c (_bfd_riscv_get_max_alignment_in_gp): New.
	(_bfd_riscv_relax_lui): The max_alignment of sections is from
	[gp-2K, gp+2K).
	(_bfd_riscv_relax_pc): Likewise.
ld/
	* ld/testsuite/ld-riscv-elf/relax-max-align.*: New tests.
---
 bfd/elfnn-riscv.c                           | 36 ++++++++++++++++
 ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp  |  1 +
 ld/testsuite/ld-riscv-elf/relax-max-align.d | 46 +++++++++++++++++++++
 ld/testsuite/ld-riscv-elf/relax-max-align.s | 29 +++++++++++++
 4 files changed, 112 insertions(+)
 create mode 100644 ld/testsuite/ld-riscv-elf/relax-max-align.d
 create mode 100644 ld/testsuite/ld-riscv-elf/relax-max-align.s

diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index 3d2ddf4e651..76f888d805c 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -4262,6 +4262,28 @@ _bfd_riscv_get_max_alignment (asection *sec)
   return (bfd_vma) 1 << max_alignment_power;
 }
 
+/* Traverse all output sections in [gp-2K, gp+2K) and return the max alignment.  */
+
+static bfd_vma
+_bfd_riscv_get_max_alignment_in_gp (asection *sec, bfd_vma gp)
+{
+  unsigned int max_alignment_power = 0;
+  asection *o;
+
+  if (sec == NULL)
+    return 0;
+
+  for (o = sec->output_section->owner->sections; o != NULL; o = o->next)
+    {
+      if (VALID_ITYPE_IMM (sec_addr(o) - gp)
+	  || VALID_ITYPE_IMM (sec_addr(o) + o->size - gp))
+	if (o->alignment_power > max_alignment_power)
+	  max_alignment_power = o->alignment_power;
+    }
+
+  return (bfd_vma) 1 << max_alignment_power;
+}
+
 /* Relax non-PIC global variable references to GP-relative references.  */
 
 static bool
@@ -4293,6 +4315,13 @@ _bfd_riscv_relax_lui (bfd *abfd,
       if (h->u.def.section->output_section == sym_sec->output_section
 	  && sym_sec->output_section != bfd_abs_section_ptr)
 	max_alignment = (bfd_vma) 1 << sym_sec->output_section->alignment_power;
+
+      /* Otherwise, consider the alignment of sections in [gp-2K,gp+2K). */
+      else if (!undefined_weak){
+	  bfd_vma new_max_alignment = _bfd_riscv_get_max_alignment_in_gp (sym_sec, gp);
+	  if (new_max_alignment)
+	    max_alignment = new_max_alignment;
+      }
     }
 
   /* Is the reference in range of x0 or gp?
@@ -4559,6 +4588,13 @@ _bfd_riscv_relax_pc (bfd *abfd ATTRIBUTE_UNUSED,
       if (h->u.def.section->output_section == sym_sec->output_section
 	  && sym_sec->output_section != bfd_abs_section_ptr)
 	max_alignment = (bfd_vma) 1 << sym_sec->output_section->alignment_power;
+
+      /* Otherwise, consider the alignment of sections in [gp-2K,gp+2K). */
+      else if (!undefined_weak){
+	  bfd_vma new_max_alignment = _bfd_riscv_get_max_alignment_in_gp (sym_sec, gp);
+	  if (new_max_alignment)
+	    max_alignment = new_max_alignment;
+      }
     }
 
   /* Is the reference in range of x0 or gp?
diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
index df89e0ee68b..e53f16facfa 100644
--- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
+++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
@@ -169,6 +169,7 @@ if [istarget "riscv*-*-*"] {
     run_dump_test "attr-merge-priv-spec-failed-05"
     run_dump_test "attr-merge-priv-spec-failed-06"
     run_dump_test "attr-phdr"
+    run_dump_test "relax-max-align"
     run_ld_link_tests [list \
 	[list "Weak reference 32" "-T weakref.ld -m[riscv_choose_ilp32_emul]" "" \
 	    "-march=rv32i -mabi=ilp32" {weakref32.s} \
diff --git a/ld/testsuite/ld-riscv-elf/relax-max-align.d b/ld/testsuite/ld-riscv-elf/relax-max-align.d
new file mode 100644
index 00000000000..4ba920da970
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/relax-max-align.d
@@ -0,0 +1,46 @@
+#source: relax-max-align.s
+#ld:
+#objdump: -d
+
+.*:[ 	]+file format .*
+
+
+Disassembly of section .text:
+
+0+[0-9a-f]+ <_start>:
+.*:[ 	]+[0-9a-f]+[ 	]+addi[ 	]+.*<gdata>
+.*:[ 	]+[0-9a-f]+[ 	]+jal[ 	]+.*
+.*:[ 	]+[0-9a-f]+[ 	]+j[ 	]+.*
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+.*:[ 	]+[0-9a-f]+[ 	]+nop
+
+0+[0-9a-f]+ <func>:
+.*:[ 	]+[0-9a-f]+[ 	]+ret
+[ 	]+...
diff --git a/ld/testsuite/ld-riscv-elf/relax-max-align.s b/ld/testsuite/ld-riscv-elf/relax-max-align.s
new file mode 100644
index 00000000000..e8abe0f34a1
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/relax-max-align.s
@@ -0,0 +1,29 @@
+
+.global _start
+_start:
+	lui   a0, %hi(gdata)
+	addi  a0, a0, %lo(gdata)
+	call func
+	j .
+	.size _start, . - _start
+
+.global func
+.align 7
+func:
+	ret
+	.size func, . - func
+
+.data
+padding:
+	.long 0
+	.long 0
+	.long 0
+	.long 0
+	.size padding, . - padding
+
+.global gdata
+.type gdata, object
+gdata:
+	.zero 4
+	.size gdata, . - gdata
+	
-- 
2.32.1 (Apple Git-133)