[RISCV] Put data smaller than eight bytes to small data section

Because of gp = sdata_start_address + 0x800, gp with signed twelve-bit offset
could covert most of the small data section. Linker relaxation could transfer
the multiple data accessing instructions to a gp base with signed twelve-bit
offset instruction.

Differential Revision: https://reviews.llvm.org/D57493

llvm-svn: 358150

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/RISCVTargetObjectFile.h b/llvm/lib/Target/RISCV/RISCVTargetObjectFile.h
index e622c5a6c1a..b2daaaa9d36 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetObjectFile.h
+++ b/llvm/lib/Target/RISCV/RISCVTargetObjectFile.h
@@ -16,7 +16,31 @@ class RISCVTargetMachine;
 
 /// This implementation is used for RISCV ELF targets.
 class RISCVELFTargetObjectFile : public TargetLoweringObjectFileELF {
+  MCSection *SmallDataSection;
+  MCSection *SmallBSSSection;
+  unsigned SSThreshold = 8;
+
+public:
   void Initialize(MCContext &Ctx, const TargetMachine &TM) override;
+
+  /// Return true if this global address should be placed into small data/bss
+  /// section.
+  bool isGlobalInSmallSection(const GlobalObject *GO,
+                              const TargetMachine &TM) const;
+
+  MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
+                                    const TargetMachine &TM) const override;
+
+  /// Return true if this constant should be placed into small data section.
+  bool isConstantInSmallSection(const DataLayout &DL, const Constant *CN) const;
+
+  MCSection *getSectionForConstant(const DataLayout &DL, SectionKind Kind,
+                                   const Constant *C,
+                                   unsigned &Align) const override;
+
+  void getModuleMetadata(Module &M) override;
+
+  bool isInSmallSection(uint64_t Size) const;
 };
 
 } // end namespace llvm