Commits on Dec 1, 2019

1. [RISCV] Fix evaluation of %pcrel_lo …

   The following testcase
   
     function:
     .Lpcrel_label1:
     	auipc	a0, %pcrel_hi(other_function)
     	addi	a1, a0, %pcrel_lo(.Lpcrel_label1)
     	.p2align	2          # Causes a new fragment to be emitted
   
     	.type	other_function,@function
     other_function:
     	ret
   
   exposes an odd behaviour in which only the %pcrel_hi relocation is
   evaluated but not the %pcrel_lo.
   
     $ llvm-mc -triple riscv64 -filetype obj t.s | llvm-objdump  -d -r -
   
     <stdin>:	file format ELF64-riscv
   
     Disassembly of section .text:
     0000000000000000 function:
            0:	17 05 00 00	auipc	a0, 0
            4:	93 05 05 00	mv	a1, a0
     		0000000000000004:  R_RISCV_PCREL_LO12_I	other_function+4
   
     0000000000000008 other_function:
            8:	67 80 00 00	ret
   
   The reason seems to be that in RISCVAsmBackend::shouldForceRelocation we
   only consider the fragment but in RISCVMCExpr::evaluatePCRelLo we
   consider the section. This usually works but there are cases where the
   section may still be the same but the fragment may be another one. In
   that case we end forcing a %pcrel_lo relocation without any %pcrel_hi.
   
   This patch makes RISCVAsmBackend::shouldForceRelocation use the section,
   if any, to determine if the relocation must be forced or not.
   
   Differential Revision: https://reviews.llvm.org/D60657

   

   rofirrim authored and msizanoen1 committed Dec 1, 2019
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