File riscv-eh-frame-fixup.patch of Package llvm9.13190
commit 7cb3cd34e8d
Author: Alex Bradbury <asb@lowrisc.org>
Date: Tue Aug 20 12:32:31 2019 +0000
[RISCV] Implement getExprForFDESymbol to ensure RISCV_32_PCREL is used for the FDE location
Follow binutils in using RISCV_32_PCREL for the FDE initial location. As
explained in the relevant binutils commit
<https://github.com/riscv/riscv-binutils-gdb/commit/a6cbf936e3dce68114d28cdf60d510a3f78a6d40>,
the ADD/SUB pair of relocations is problematic in the presence of linker
relaxation.
This patch has the same end goal as D64715 but includes test changes and
avoids adding a new global VariantKind to MCExpr.h (preferring
RISCVMCExpr VKs like the rest of the RISC-V backend).
Differential Revision: https://reviews.llvm.org/D66419
llvm-svn: 369375
commit 1c1f8f215d8
Author: Alex Bradbury <asb@lowrisc.org>
Date: Mon Aug 19 13:23:02 2019 +0000
[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
commit 49a99788393
Author: Hsiangkai Wang <hsiangkai@gmail.com>
Date: Fri Jul 19 06:10:36 2019 +0000
[DebugInfo] Some fields do not need relocations even relax is enabled.
In debug frame information, some fields, e.g., Length in CIE/FDE and
Offset in FDE are attributes to describe the structure of CIE/FDE. They
are not related to the relaxed code. However, these attributes are
symbol differences. So, in current design, these attributes will be
filled as zero and LLVM generates relocations for them.
We only need to generate relocations for symbols in executable sections.
So, if the symbols are not located in executable sections, we still
evaluate their values under relaxation.
Differential Revision: https://reviews.llvm.org/D61584
llvm-svn: 366531
Index: llvm-9.0.1.src/lib/MC/MCExpr.cpp
===================================================================
--- llvm-9.0.1.src.orig/lib/MC/MCExpr.cpp
+++ llvm-9.0.1.src/lib/MC/MCExpr.cpp
@@ -577,6 +577,24 @@ static void AttemptToFoldSymbolOffsetDif
A = B = nullptr;
}
+static bool canFold(const MCAssembler *Asm, const MCSymbolRefExpr *A,
+ const MCSymbolRefExpr *B, bool InSet) {
+ if (InSet)
+ return true;
+
+ if (!Asm->getBackend().requiresDiffExpressionRelocations())
+ return true;
+
+ const MCSymbol &CheckSym = A ? A->getSymbol() : B->getSymbol();
+ if (!CheckSym.isInSection())
+ return true;
+
+ if (!CheckSym.getSection().hasInstructions())
+ return true;
+
+ return false;
+}
+
/// Evaluate the result of an add between (conceptually) two MCValues.
///
/// This routine conceptually attempts to construct an MCValue:
@@ -617,8 +635,7 @@ EvaluateSymbolicAdd(const MCAssembler *A
// the backend requires this to be emitted as individual relocations, unless
// the InSet flag is set to get the current difference anyway (used for
// example to calculate symbol sizes).
- if (Asm &&
- (InSet || !Asm->getBackend().requiresDiffExpressionRelocations())) {
+ if (Asm && canFold(Asm, LHS_A, LHS_B, InSet)) {
// First, fold out any differences which are fully resolved. By
// reassociating terms in
// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
Index: llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
===================================================================
--- llvm-9.0.1.src.orig/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
+++ llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
@@ -33,6 +33,13 @@ bool RISCVAsmBackend::shouldForceRelocat
switch ((unsigned)Fixup.getKind()) {
default:
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_tls_got_hi20:
case RISCV::fixup_riscv_tls_gd_hi20:
Index: llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
===================================================================
--- llvm-9.0.1.src.orig/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
+++ llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
@@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/RISCVFixupKinds.h"
+#include "MCTargetDesc/RISCVMCExpr.h"
#include "MCTargetDesc/RISCVMCTargetDesc.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCFixup.h"
@@ -47,6 +48,7 @@ unsigned RISCVELFObjectWriter::getRelocT
const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const {
+ const MCExpr *Expr = Fixup.getValue();
// Determine the type of the relocation
unsigned Kind = Fixup.getKind();
if (IsPCRel) {
@@ -87,6 +89,9 @@ unsigned RISCVELFObjectWriter::getRelocT
default:
llvm_unreachable("invalid fixup kind!");
case FK_Data_4:
+ if (Expr->getKind() == MCExpr::Target &&
+ cast<RISCVMCExpr>(Expr)->getKind() == RISCVMCExpr::VK_RISCV_32_PCREL)
+ return ELF::R_RISCV_32_PCREL;
return ELF::R_RISCV_32;
case FK_Data_8:
return ELF::R_RISCV_64;
Index: llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp
===================================================================
--- llvm-9.0.1.src.orig/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp
+++ llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp
@@ -11,7 +11,10 @@
//===----------------------------------------------------------------------===//
#include "RISCVMCAsmInfo.h"
+#include "MCTargetDesc/RISCVMCExpr.h"
#include "llvm/ADT/Triple.h"
+#include "llvm/BinaryFormat/Dwarf.h"
+#include "llvm/MC/MCStreamer.h"
using namespace llvm;
void RISCVMCAsmInfo::anchor() {}
@@ -25,3 +28,20 @@ RISCVMCAsmInfo::RISCVMCAsmInfo(const Tri
Data16bitsDirective = "\t.half\t";
Data32bitsDirective = "\t.word\t";
}
+
+const MCExpr *RISCVMCAsmInfo::getExprForFDESymbol(const MCSymbol *Sym,
+ unsigned Encoding,
+ MCStreamer &Streamer) const {
+ if (!(Encoding & dwarf::DW_EH_PE_pcrel))
+ return MCAsmInfo::getExprForFDESymbol(Sym, Encoding, Streamer);
+
+ // The default symbol subtraction results in an ADD/SUB relocation pair.
+ // Processing this relocation pair is problematic when linker relaxation is
+ // enabled, so we follow binutils in using the R_RISCV_32_PCREL relocation
+ // for the FDE initial location.
+ MCContext &Ctx = Streamer.getContext();
+ const MCExpr *ME =
+ MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_None, Ctx);
+ assert(Encoding & dwarf::DW_EH_PE_sdata4 && "Unexpected encoding");
+ return RISCVMCExpr::create(ME, RISCVMCExpr::VK_RISCV_32_PCREL, Ctx);
+}
Index: llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.h
===================================================================
--- llvm-9.0.1.src.orig/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.h
+++ llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.h
@@ -23,6 +23,9 @@ class RISCVMCAsmInfo : public MCAsmInfoE
public:
explicit RISCVMCAsmInfo(const Triple &TargetTriple);
+
+ const MCExpr *getExprForFDESymbol(const MCSymbol *Sym, unsigned Encoding,
+ MCStreamer &Streamer) const override;
};
} // namespace llvm
Index: llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
===================================================================
--- llvm-9.0.1.src.orig/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
+++ llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
@@ -266,6 +266,7 @@ unsigned RISCVMCCodeEmitter::getImmOpVal
switch (RVExpr->getKind()) {
case RISCVMCExpr::VK_RISCV_None:
case RISCVMCExpr::VK_RISCV_Invalid:
+ case RISCVMCExpr::VK_RISCV_32_PCREL:
llvm_unreachable("Unhandled fixup kind!");
case RISCVMCExpr::VK_RISCV_TPREL_ADD:
// tprel_add is only used to indicate that a relocation should be emitted
Index: llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.h
===================================================================
--- llvm-9.0.1.src.orig/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.h
+++ llvm-9.0.1.src/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.h
@@ -36,6 +36,7 @@ public:
VK_RISCV_TLS_GD_HI,
VK_RISCV_CALL,
VK_RISCV_CALL_PLT,
+ VK_RISCV_32_PCREL,
VK_RISCV_Invalid
};
Index: llvm-9.0.1.src/test/DebugInfo/RISCV/dwarf-riscv-relocs.ll
===================================================================
--- llvm-9.0.1.src.orig/test/DebugInfo/RISCV/dwarf-riscv-relocs.ll
+++ llvm-9.0.1.src/test/DebugInfo/RISCV/dwarf-riscv-relocs.ll
@@ -6,14 +6,14 @@
; Check that we actually have relocations, otherwise this is kind of pointless.
; READOBJ-RELOCS: Section (8) .rela.debug_info {
-; READOBJ-RELOCS-NEXT: 0x0 R_RISCV_ADD32 - 0x0
-; READOBJ-RELOCS-NEXT: 0x0 R_RISCV_SUB32 - 0x0
-; READOBJ-RELOCS: Section (11) .rela.debug_addr {
-; READOBJ-RELOCS-NEXT: 0x0 R_RISCV_ADD32 - 0x0
-; READOBJ-RELOCS-NEXT: 0x0 R_RISCV_SUB32 - 0x0
+; READOBJ-RELOCS: 0x1B R_RISCV_ADD32 - 0x0
+; READOBJ-RELOCS-NEXT: 0x1B R_RISCV_SUB32 - 0x0
+; READOBJ-RELOCS: Section (15) .rela.debug_frame {
+; READOBJ-RELOCS: 0x20 R_RISCV_ADD32 - 0x0
+; READOBJ-RELOCS-NEXT: 0x20 R_RISCV_SUB32 - 0x0
; READOBJ-RELOCS: Section (17) .rela.debug_line {
-; READOBJ-RELOCS-NEXT: 0x0 R_RISCV_ADD32 - 0xFFFFFFFC
-; READOBJ-RELOCS-NEXT: 0x0 R_RISCV_SUB32 .Lline_table_start0 0x0
+; READOBJ-RELOCS: 0x5A R_RISCV_ADD16 - 0x0
+; READOBJ-RELOCS-NEXT: 0x5A R_RISCV_SUB16 - 0x0
; Check that we can print the source, even with relocations.
; OBJDUMP-SOURCE: Disassembly of section .text:
Index: llvm-9.0.1.src/test/MC/RISCV/fde-reloc.s
===================================================================
--- llvm-9.0.1.src.orig/test/MC/RISCV/fde-reloc.s
+++ llvm-9.0.1.src/test/MC/RISCV/fde-reloc.s
@@ -8,20 +8,8 @@ func:
ret
.cfi_endproc
-# TODO: Should produce R_RISCV_32_PCREL for the FDE pc relocation. Many of the
-# ADD32/SUB32 relocations also can be safely resolved even with linker
-# relaxation enabled. This test is written to capture current behaviour, in
-# preparation for follow-on patches to fix it.
-
# RELAX-RELOC: Section (4) .rela.eh_frame {
-# RELAX-RELOC-NEXT: 0x0 R_RISCV_ADD32 - 0xFFFFFFFC
-# RELAX-RELOC-NEXT: 0x0 R_RISCV_SUB32 - 0x0
-# RELAX-RELOC-NEXT: 0x14 R_RISCV_ADD32 - 0x0
-# RELAX-RELOC-NEXT: 0x14 R_RISCV_SUB32 - 0x0
-# RELAX-RELOC-NEXT: 0x18 R_RISCV_ADD32 - 0x0
-# RELAX-RELOC-NEXT: 0x18 R_RISCV_SUB32 - 0x0
-# RELAX-RELOC-NEXT: 0x1C R_RISCV_ADD32 - 0x0
-# RELAX-RELOC-NEXT: 0x1C R_RISCV_SUB32 - 0x0
+# RELAX-RELOC-NEXT: 0x1C R_RISCV_32_PCREL - 0x0
# RELAX-RELOC-NEXT: 0x20 R_RISCV_ADD32 - 0x0
# RELAX-RELOC-NEXT: 0x20 R_RISCV_SUB32 - 0x0
# RELAX-RELOC-NEXT: }
Index: llvm-9.0.1.src/test/MC/RISCV/linker-relaxation.s
===================================================================
--- llvm-9.0.1.src.orig/test/MC/RISCV/linker-relaxation.s
+++ llvm-9.0.1.src/test/MC/RISCV/linker-relaxation.s
@@ -136,3 +136,24 @@ sb t1, %pcrel_lo(2b)(a2)
# 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 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:
