[Hexagon] Adding relocation for code size, cold path optimization allowing a 23-bit...

The usual way to get a 32-bit relocation is to use a constant extender which doubles the size of the instruction, 4 bytes to 8 bytes.

Another way is to put a .word32 and mix code and data within a function.  The disadvantage is it's not a valid instruction encoding and jumping over it causes prefetch stalls inside the hardware.

This relocation packs a 23-bit value in to an "r0 = add(rX, #a)" instruction by overwriting the source register bits.  Since r0 is the return value register, if this instruction is placed after a function call which return void, r0 will be filled with an undefined value, the prefetch won't be confused, and the callee can access the constant value by way of the link register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261006 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/ELFRelocs/Hexagon.def b/include/llvm/Support/ELFRelocs/Hexagon.def
index a698ecb..74e1d40 100644 (file)
--- a/include/llvm/Support/ELFRelocs/Hexagon.def
+++ b/include/llvm/Support/ELFRelocs/Hexagon.def
@@ -98,3 +98,4 @@ ELF_RELOC(R_HEX_LD_GOT_16,           90)
 ELF_RELOC(R_HEX_LD_GOT_32_6_X,       91)
 ELF_RELOC(R_HEX_LD_GOT_16_X,         92)
 ELF_RELOC(R_HEX_LD_GOT_11_X,         93)
+ELF_RELOC(R_HEX_23_REG,              94)

diff --git a/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp b/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp
index 8b8eb4a..b6d10f7 100644 (file)
--- a/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp
+++ b/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp
@@ -278,6 +278,7 @@ public:
 
   bool isf32Ext() const { return false; }
   bool iss32Imm() const { return CheckImmRange(32, 0, true, true, false); }
+  bool iss23_2Imm() const { return CheckImmRange(23, 2, true, true, false); }
   bool iss8Imm() const { return CheckImmRange(8, 0, true, false, false); }
   bool iss8Imm64() const { return CheckImmRange(8, 0, true, true, false); }
   bool iss7Imm() const { return CheckImmRange(7, 0, true, false, false); }
@@ -384,6 +385,9 @@ public:
   void adds32ImmOperands(MCInst &Inst, unsigned N) const {
     addSignedImmOperands(Inst, N);
   }
+  void adds23_2ImmOperands(MCInst &Inst, unsigned N) const {
+    addSignedImmOperands(Inst, N);
+  }
   void adds8ImmOperands(MCInst &Inst, unsigned N) const {
     addSignedImmOperands(Inst, N);
   }
@@ -1543,6 +1547,18 @@ int HexagonAsmParser::processInstruction(MCInst &Inst,
   default:
     break;
 
+  case Hexagon::A2_iconst: {
+    Inst.setOpcode(Hexagon::A2_addi);
+    MCOperand Reg = Inst.getOperand(0);
+    MCOperand S16 = Inst.getOperand(1);
+    HexagonMCInstrInfo::setMustNotExtend(*S16.getExpr());
+    HexagonMCInstrInfo::setS23_2_reloc(*S16.getExpr());
+    Inst.clear();
+    Inst.addOperand(Reg);
+    Inst.addOperand(MCOperand::createReg(Hexagon::R0));
+    Inst.addOperand(S16);
+    break;
+  }
   case Hexagon::M4_mpyrr_addr:
   case Hexagon::S4_addi_asl_ri:
   case Hexagon::S4_addi_lsr_ri:

diff --git a/lib/Target/Hexagon/HexagonAsmPrinter.cpp b/lib/Target/Hexagon/HexagonAsmPrinter.cpp
index 208f02f..48f3e31 100644 (file)
--- a/lib/Target/Hexagon/HexagonAsmPrinter.cpp
+++ b/lib/Target/Hexagon/HexagonAsmPrinter.cpp
@@ -264,6 +264,19 @@ void HexagonAsmPrinter::HexagonProcessInstruction(MCInst &Inst,
   switch (Inst.getOpcode()) {
   default: return;
 
+  case Hexagon::A2_iconst: {
+    Inst.setOpcode(Hexagon::A2_addi);
+    MCOperand Reg = Inst.getOperand(0);
+    MCOperand S16 = Inst.getOperand(1);
+    HexagonMCInstrInfo::setMustNotExtend(*S16.getExpr());
+    HexagonMCInstrInfo::setS23_2_reloc(*S16.getExpr());
+    Inst.clear();
+    Inst.addOperand(Reg);
+    Inst.addOperand(MCOperand::createReg(Hexagon::R0));
+    Inst.addOperand(S16);
+    break;
+  }
+
   // "$dst = CONST64(#$src1)",
   case Hexagon::CONST64_Float_Real:
   case Hexagon::CONST64_Int_Real:

diff --git a/lib/Target/Hexagon/HexagonInstrInfo.td b/lib/Target/Hexagon/HexagonInstrInfo.td
index b209ff8..6424022 100644 (file)
--- a/lib/Target/Hexagon/HexagonInstrInfo.td
+++ b/lib/Target/Hexagon/HexagonInstrInfo.td
@@ -418,6 +418,12 @@ defm addi : Addri_base<"add", add>, ImmRegRel, PredNewRel;
 def: Pat<(i32 (add I32:$Rs, s32ImmPred:$s16)),
          (i32 (A2_addi I32:$Rs, imm:$s16))>;
 
+let hasNewValue = 1, hasSideEffects = 0, isPseudo = 1 in
+def A2_iconst
+  : ALU32_ri <(outs IntRegs:$Rd),
+              (ins s23_2Imm:$s23_2),
+  "$Rd = iconst(#$s23_2)"> {}
+
 //===----------------------------------------------------------------------===//
 // Template class used for the following ALU32 instructions.
 // Rd=and(Rs,#s10)

diff --git a/lib/Target/Hexagon/HexagonOperands.td b/lib/Target/Hexagon/HexagonOperands.td
index fbd29cd..7224bb6 100644 (file)
--- a/lib/Target/Hexagon/HexagonOperands.td
+++ b/lib/Target/Hexagon/HexagonOperands.td
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 def s32ImmOperand : AsmOperandClass { let Name = "s32Imm"; }
+def s23_2ImmOperand : AsmOperandClass { let Name = "s23_2Imm"; }
 def s8ImmOperand : AsmOperandClass { let Name = "s8Imm"; }
 def s8Imm64Operand : AsmOperandClass { let Name = "s8Imm64"; }
 def s6ImmOperand : AsmOperandClass { let Name = "s6Imm"; }
@@ -48,6 +49,7 @@ let OperandType = "OPERAND_IMMEDIATE",
     DecoderMethod = "unsignedImmDecoder" in {
   def s32Imm : Operand<i32> { let ParserMatchClass = s32ImmOperand;
                               let DecoderMethod = "s32ImmDecoder"; }
+  def s23_2Imm : Operand<i32> { let ParserMatchClass = s23_2ImmOperand; }
   def s8Imm : Operand<i32> { let ParserMatchClass = s8ImmOperand;
                              let DecoderMethod = "s8ImmDecoder"; }
   def s8Imm64 : Operand<i64>  { let ParserMatchClass = s8Imm64Operand;

diff --git a/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp b/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp
index 4f03c97..944e235 100644 (file)
--- a/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp
+++ b/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp
@@ -282,6 +282,8 @@ unsigned HexagonELFObjectWriter::getRelocType(MCContext &Ctx,
     return ELF::R_HEX_TPREL_16_X;
   case fixup_Hexagon_TPREL_11_X:
     return ELF::R_HEX_TPREL_11_X;
+  case fixup_Hexagon_23_REG:
+    return ELF::R_HEX_23_REG;
   }
 }
 

diff --git a/lib/Target/Hexagon/MCTargetDesc/HexagonFixupKinds.h b/lib/Target/Hexagon/MCTargetDesc/HexagonFixupKinds.h
index 4bbfbec..4c97ebb 100644 (file)
--- a/lib/Target/Hexagon/MCTargetDesc/HexagonFixupKinds.h
+++ b/lib/Target/Hexagon/MCTargetDesc/HexagonFixupKinds.h
@@ -110,6 +110,7 @@ enum Fixups {
   fixup_Hexagon_TPREL_32_6_X,
   fixup_Hexagon_TPREL_16_X,
   fixup_Hexagon_TPREL_11_X,
+  fixup_Hexagon_23_REG,
 
   LastTargetFixupKind,
   NumTargetFixupKinds = LastTargetFixupKind - FirstTargetFixupKind

diff --git a/lib/Target/Hexagon/MCTargetDesc/HexagonMCCodeEmitter.cpp b/lib/Target/Hexagon/MCTargetDesc/HexagonMCCodeEmitter.cpp
index fcc9fcd..d4eb2fc 100644 (file)
--- a/lib/Target/Hexagon/MCTargetDesc/HexagonMCCodeEmitter.cpp
+++ b/lib/Target/Hexagon/MCTargetDesc/HexagonMCCodeEmitter.cpp
@@ -550,6 +550,13 @@ unsigned HexagonMCCodeEmitter::getExprOpValue(const MCInst &MI,
       }
     } else
       switch (kind) {
+      case MCSymbolRefExpr::VK_None: {
+        if (HexagonMCInstrInfo::s23_2_reloc(*MO.getExpr()))
+          FixupKind = Hexagon::fixup_Hexagon_23_REG;
+        else
+          raise_relocation_error(bits, kind);
+        break;
+      }
       case MCSymbolRefExpr::VK_DTPREL:
         FixupKind = Hexagon::fixup_Hexagon_DTPREL_16;
         break;

diff --git a/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.cpp b/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.cpp
index d3ee314..8a83e7b 100644 (file)
--- a/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.cpp
+++ b/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.cpp
@@ -52,12 +52,17 @@ void HexagonMCExpr::setMustNotExtend(bool Val) {
 }
 bool HexagonMCExpr::mustNotExtend() const { return MustNotExtend; }
 
+bool HexagonMCExpr::s23_2_reloc() const { return S23_2_reloc; }
+void HexagonMCExpr::setS23_2_reloc(bool Val) {
+  S23_2_reloc = Val;
+}
+
 bool HexagonMCExpr::classof(MCExpr const *E) {
   return E->getKind() == MCExpr::Target;
 }
 
 HexagonMCExpr::HexagonMCExpr(MCExpr const *Expr)
-    : Expr(Expr), MustNotExtend(false), MustExtend(false) {}
+    : Expr(Expr), MustNotExtend(false), MustExtend(false), S23_2_reloc(false) {}
 
 void HexagonMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const {
   Expr->print(OS, MAI);

diff --git a/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.h b/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.h
index e16d926..1396f2d 100644 (file)
--- a/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.h
+++ b/lib/Target/Hexagon/MCTargetDesc/HexagonMCExpr.h
@@ -29,12 +29,15 @@ public:
   bool mustExtend() const;
   void setMustNotExtend(bool Val = true);
   bool mustNotExtend() const;
+  void setS23_2_reloc(bool Val = true);
+  bool s23_2_reloc() const;
 
 private:
   HexagonMCExpr(MCExpr const *Expr);
   MCExpr const *Expr;
   bool MustNotExtend;
   bool MustExtend;
+  bool S23_2_reloc;
 };
 } // end namespace llvm
 

diff --git a/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.cpp b/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.cpp
index 9b3d11a..fb585b9 100644 (file)
--- a/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.cpp
+++ b/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.cpp
@@ -431,6 +431,9 @@ bool HexagonMCInstrInfo::isConstExtended(MCInstrInfo const &MCII,
   // object we are going to end up with here for now.
   // In the future we probably should add isSymbol(), etc.
   assert(!MO.isImm());
+  if (isa<HexagonMCExpr>(MO.getExpr()) &&
+      HexagonMCInstrInfo::mustNotExtend(*MO.getExpr()))
+    return false;
   int64_t Value;
   if (!MO.getExpr()->evaluateAsAbsolute(Value))
     return true;
@@ -665,6 +668,15 @@ void HexagonMCInstrInfo::setMemStoreReorderEnabled(MCInst &MCI) {
   Operand.setImm(Operand.getImm() | memStoreReorderEnabledMask);
   assert(isMemStoreReorderEnabled(MCI));
 }
+void HexagonMCInstrInfo::setS23_2_reloc(MCExpr const &Expr, bool Val) {
+  HexagonMCExpr &HExpr =
+      const_cast<HexagonMCExpr &>(*llvm::cast<HexagonMCExpr>(&Expr));
+  HExpr.setS23_2_reloc(Val);
+}
+bool HexagonMCInstrInfo::s23_2_reloc(MCExpr const &Expr) {
+  HexagonMCExpr const &HExpr = *llvm::cast<HexagonMCExpr>(&Expr);
+  return HExpr.s23_2_reloc();
+}
 
 void HexagonMCInstrInfo::setOuterLoop(MCInst &MCI) {
   assert(isBundle(MCI));

diff --git a/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.h b/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.h
index 6bfcabf..c9162a6 100644 (file)
--- a/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.h
+++ b/lib/Target/Hexagon/MCTargetDesc/HexagonMCInstrInfo.h
@@ -274,12 +274,14 @@ bool prefersSlot3(MCInstrInfo const &MCII, MCInst const &MCI);
 // Replace the instructions inside MCB, represented by Candidate
 void replaceDuplex(MCContext &Context, MCInst &MCB, DuplexCandidate Candidate);
 
+bool s23_2_reloc(MCExpr const &Expr);
 // Marks a bundle as endloop0
 void setInnerLoop(MCInst &MCI);
 void setMemReorderDisabled(MCInst &MCI);
 void setMemStoreReorderEnabled(MCInst &MCI);
 void setMustExtend(MCExpr &Expr, bool Val = true);
 void setMustNotExtend(MCExpr const &Expr, bool Val = true);
+void setS23_2_reloc(MCExpr const &Expr, bool Val = true);
 
 // Marks a bundle as endloop1
 void setOuterLoop(MCInst &MCI);

diff --git a/test/MC/Hexagon/iconst.s b/test/MC/Hexagon/iconst.s
new file mode 100644 (file)
index 0000000..277c4de
--- /dev/null
+++ b/test/MC/Hexagon/iconst.s
@@ -0,0 +1,6 @@
+# RUN: llvm-mc -triple=hexagon -filetype=obj %s | llvm-objdump -d -r - | FileCheck %s
+
+a:
+# CHECK: r0 = add(r0, #0)
+# CHECK: R_HEX_23_REG
+r0 = iconst(#a)
\ No newline at end of file