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[RISCV] Don't force absolute FK_Data_X fixups to relocs 

The current behavior of shouldForceRelocation forces relocations for the
majority of fixups when relaxation is enabled. This makes sense for
fixups which incorporate symbols but is unnecessary for simple data
fixups where the fixup target is already resolved to an absolute value.

Differential Revision: https://reviews.llvm.org/D63404
Patch by Edward Jones.

llvm-svn: 369257
This commit is contained in:
Alex Bradbury 2019-08-19 13:23:02 +00:00
parent 88df53e6ea
commit 1c1f8f215d
3 changed files with 28 additions and 3 deletions
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7
llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
View File

@ -33,6 +33,13 @@ bool RISCVAsmBackend::shouldForceRelocation(const MCAssembler &Asm,
switch ((unsigned)Fixup.getKind()) { switch ((unsigned)Fixup.getKind()) {
default: default:
break; break;
case FK_Data_1:
case FK_Data_2:
case FK_Data_4:
case FK_Data_8:
if (Target.isAbsolute())
return false;
break;
case RISCV::fixup_riscv_got_hi20: case RISCV::fixup_riscv_got_hi20:
case RISCV::fixup_riscv_tls_got_hi20: case RISCV::fixup_riscv_tls_got_hi20:
case RISCV::fixup_riscv_tls_gd_hi20: case RISCV::fixup_riscv_tls_gd_hi20:

3
llvm/test/MC/RISCV/fde-reloc.s
View File

@ -14,9 +14,6 @@ func:
# preparation for follow-on patches to fix it. # preparation for follow-on patches to fix it.
# RELAX-RELOC: Section (4) .rela.eh_frame { # RELAX-RELOC: Section (4) .rela.eh_frame {
# RELAX-RELOC-NEXT: 0x0 R_RISCV_32 - 0x10
# RELAX-RELOC-NEXT: 0x14 R_RISCV_32 - 0x10
# RELAX-RELOC-NEXT: 0x18 R_RISCV_32 - 0x18
# RELAX-RELOC-NEXT: 0x1C R_RISCV_ADD32 - 0x0 # RELAX-RELOC-NEXT: 0x1C R_RISCV_ADD32 - 0x0
# RELAX-RELOC-NEXT: 0x1C R_RISCV_SUB32 - 0x0 # RELAX-RELOC-NEXT: 0x1C R_RISCV_SUB32 - 0x0
# RELAX-RELOC-NEXT: 0x20 R_RISCV_ADD32 - 0x0 # RELAX-RELOC-NEXT: 0x20 R_RISCV_ADD32 - 0x0

21
llvm/test/MC/RISCV/linker-relaxation.s
View File

@ -136,3 +136,24 @@ sb t1, %pcrel_lo(2b)(a2)
# RELAX-RELOC: R_RISCV_RELAX - 0x0 # RELAX-RELOC: R_RISCV_RELAX - 0x0
# RELAX-FIXUP: fixup A - offset: 0, value: %pcrel_lo(.Ltmp1), kind: fixup_riscv_pcrel_lo12_s # RELAX-FIXUP: fixup A - offset: 0, value: %pcrel_lo(.Ltmp1), kind: fixup_riscv_pcrel_lo12_s
# RELAX-FIXUP: fixup B - offset: 0, value: 0, kind: fixup_riscv_relax # RELAX-FIXUP: fixup B - offset: 0, value: 0, kind: fixup_riscv_relax
# Check that a relocation is not emitted for a symbol difference which has
# been folded to a fixup with an absolute value. This can happen when a
# difference expression refers to two symbols, at least one of which is
# not defined at the point it is referenced. Then during *assembler*
# relaxation when both symbols have become defined the difference may be folded
# down to a fixup simply containing the absolute value. We want to ensure that
# we don't force a relocation to be emitted for this absolute value even
# when linker relaxation is enabled. The reason for this is that one instance
# where this pattern appears in in the .eh_frame section (the CIE 'length'
# field), and the .eh_frame section cannot be parsed by the linker unless the
# fixup has been resolved to a concrete value instead of a relocation.
.data
lo:
.word hi-lo
.quad hi-lo
# NORELAX-RELOC-NOT: R_RISCV_32
# NORELAX-RELOC-NOT: R_RISCV_64
# RELAX-RELOC-NOT: R_RISCV_32
# RELAX-RELOC-NOT: R_RISCV_64
hi: