[RISCV] Support linker relax function call from auipc and jalr to jal

To do this: 1. Add fixup_riscv_relax fixup types which eventually will transfer to R_RISCV_RELAX relocation types. 2. Insert R_RISCV_RELAX relocation types to auipc function call expression when linker relaxation enabled. Differential Revision: https://reviews.llvm.org/D44886 llvm-svn: 333158
llvm · May 24, 2018 · 43bfe84 · 43bfe84
1 parent cfba053
commit 43bfe84
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Showing 5 changed files with 43 additions and 2 deletions.
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
@@ -88,7 +88,8 @@ class RISCVAsmBackend : public MCAsmBackend {
       { "fixup_riscv_jal",          12,     20,  MCFixupKindInfo::FKF_IsPCRel },
       { "fixup_riscv_branch",        0,     32,  MCFixupKindInfo::FKF_IsPCRel },
       { "fixup_riscv_rvc_jump",      2,     11,  MCFixupKindInfo::FKF_IsPCRel },
-      { "fixup_riscv_rvc_branch",    0,     16,  MCFixupKindInfo::FKF_IsPCRel }
+      { "fixup_riscv_rvc_branch",    0,     16,  MCFixupKindInfo::FKF_IsPCRel },
+      { "fixup_riscv_relax",         0,      0,  0 }
     };
 
     if (Kind < FirstTargetFixupKind)

diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
@@ -94,6 +94,8 @@ unsigned RISCVELFObjectWriter::getRelocType(MCContext &Ctx,
     return ELF::R_RISCV_RVC_BRANCH;
   case RISCV::fixup_riscv_call:
     return ELF::R_RISCV_CALL;
+  case RISCV::fixup_riscv_relax:
+    return ELF::R_RISCV_RELAX;
   }
 }
 

diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVFixupKinds.h b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVFixupKinds.h
@@ -50,6 +50,9 @@ enum Fixups {
   // fixup_riscv_call - A fixup representing a call attached to the auipc
   // instruction in a pair composed of adjacent auipc+jalr instructions.
   fixup_riscv_call,
+  // fixup_riscv_relax - Used to generate an R_RISCV_RELAX relocation type,
+  // which indicates the linker may relax the instruction pair.
+  fixup_riscv_relax,
 
   // fixup_riscv_invalid - used as a sentinel and a marker, must be last fixup
   fixup_riscv_invalid,

diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
@@ -186,7 +186,7 @@ RISCVMCCodeEmitter::getImmOpValueAsr1(const MCInst &MI, unsigned OpNo,
 unsigned RISCVMCCodeEmitter::getImmOpValue(const MCInst &MI, unsigned OpNo,
                                            SmallVectorImpl<MCFixup> &Fixups,
                                            const MCSubtargetInfo &STI) const {
-
+  bool EnableRelax = STI.getFeatureBits()[RISCV::FeatureRelax];
   const MCOperand &MO = MI.getOperand(OpNo);
 
   MCInstrDesc const &Desc = MCII.get(MI.getOpcode());
@@ -254,6 +254,15 @@ unsigned RISCVMCCodeEmitter::getImmOpValue(const MCInst &MI, unsigned OpNo,
       MCFixup::create(0, Expr, MCFixupKind(FixupKind), MI.getLoc()));
   ++MCNumFixups;
 
+  if (EnableRelax) {
+    if (FixupKind == RISCV::fixup_riscv_call) {
+      Fixups.push_back(
+      MCFixup::create(0, Expr, MCFixupKind(RISCV::fixup_riscv_relax),
+                      MI.getLoc()));
+      ++MCNumFixups;
+    }
+  }
+
   return 0;
 }
 

diff --git a/llvm/test/MC/RISCV/linker-relaxation.s b/llvm/test/MC/RISCV/linker-relaxation.s
@@ -0,0 +1,26 @@
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+relax < %s \
+# RUN:     | llvm-readobj -r | FileCheck -check-prefix=RELAX-RELOC %s
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=-relax < %s \
+# RUN:     | llvm-readobj -r | FileCheck -check-prefix=NORELAX-RELOC %s
+# RUN: llvm-mc -triple riscv32 -mattr=+relax < %s -show-encoding \
+# RUN:     | FileCheck -check-prefix=RELAX-FIXUP %s
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+relax < %s \
+# RUN:     | llvm-readobj -r | FileCheck -check-prefix=RELAX-RELOC %s
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=-relax < %s \
+# RUN:     | llvm-readobj -r | FileCheck -check-prefix=NORELAX-RELOC %s
+# RUN: llvm-mc -triple riscv64 -mattr=+relax < %s -show-encoding \
+# RUN:     | FileCheck -check-prefix=RELAX-FIXUP %s
+
+.long foo
+
+.L1:
+call foo
+# NORELAX-RELOC: R_RISCV_CALL foo 0x0
+# NORELAX-RELOC-NOT: R_RISCV_RELAX
+# RELAX-RELOC: R_RISCV_CALL foo 0x0
+# RELAX-RELOC: R_RISCV_RELAX foo 0x0
+# RELAX-FIXUP: fixup A - offset: 0, value: foo, kind: fixup_riscv_relax
+# RELAX-FIXUP: fixup B - offset: 0, value: foo, kind:
+beq s1, s1, .L1
+# RELAX-RELOC: R_RISCV_BRANCH .L1 0x0
+# RELAX-FIXUP: fixup A - offset: 0, value: .L1, kind: fixup_riscv_branch