svn commit: r356329 - head/contrib/llvm-project/llvm/lib/Target/RISCV/MCTargetDesc

[Dimitry Andric]

Author: dim
Date: Fri Jan  3 20:09:38 2020
New Revision: 356329
URL: https://svnweb.freebsd.org/changeset/base/356329

Log:
  Merge commit 41449c58c from llvm git (by Roger Ferrer Ibanez):
  
    [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, at 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
  
  This is a prerequisite for building and linking hard- and soft-float
  riscv worlds with clang and lld.
  
  Requested by:	jhb
  MFC after:	1 week
  X-MFC-With:	r353358

Modified:
  head/contrib/llvm-project/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp

Modified: head/contrib/llvm-project/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
==============================================================================
--- head/contrib/llvm-project/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp	Fri Jan  3 20:01:36 2020	(r356328)
+++ head/contrib/llvm-project/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp	Fri Jan  3 20:09:38 2020	(r356329)
@@ -64,10 +64,14 @@ bool RISCVAsmBackend::shouldForceRelocation(const MCAs
     case RISCV::fixup_riscv_tls_gd_hi20:
       ShouldForce = true;
       break;
-    case RISCV::fixup_riscv_pcrel_hi20:
-      ShouldForce = T->getValue()->findAssociatedFragment() !=
-                    Fixup.getValue()->findAssociatedFragment();
+    case RISCV::fixup_riscv_pcrel_hi20: {
+      MCFragment *TFragment = T->getValue()->findAssociatedFragment();
+      MCFragment *FixupFragment = Fixup.getValue()->findAssociatedFragment();
+      assert(FixupFragment && "We should have a fragment for this fixup");
+      ShouldForce =
+          !TFragment || TFragment->getParent() != FixupFragment->getParent();
       break;
+    }
     }
     break;
   }