[ELF][PPC] Simplify {read,write}FromHalf16

I've change the variable names used in PPC64.cpp from "Instr" to "Insn"
because "Insn" is a more common abbreviation for "instruction".

While changing PPC64.cpp relocateOne(), make R_PPC64_ADDR16_LO{_DS}
slightly more efficient by saving a read and a write for the TocOptimize
case.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D63043

llvm-svn: 362867

Author: MaskRay

lld/ELF/Arch/PPC.cpp

@@ -53,11 +53,11 @@ static uint16_t lo(uint32_t V) { return V; }
 static uint16_t ha(uint32_t V) { return (V + 0x8000) >> 16; }
 
 static uint32_t readFromHalf16(const uint8_t *Loc) {
-  return read32(Loc - (Config->EKind == ELF32BEKind ? 2 : 0));
+  return read32(Config->IsLE ? Loc : Loc - 2);
 }
 
 static void writeFromHalf16(uint8_t *Loc, uint32_t Insn) {
-  write32(Loc - (Config->EKind == ELF32BEKind ? 2 : 0), Insn);
+  write32(Config->IsLE ? Loc : Loc - 2, Insn);
 }
 
 void elf::writePPC32GlinkSection(uint8_t *Buf, size_t NumEntries) {

lld/ELF/Arch/PPC64.cpp

@@ -274,12 +274,12 @@ static bool isInstructionUpdateForm(uint32_t Encoding) {
 // pointer is pointing into the middle of the word we want to extract, and on
 // little-endian it is pointing to the start of the word. These 2 helpers are to
 // simplify reading and writing in that context.
-static void writeInstrFromHalf16(uint8_t *Loc, uint32_t Instr) {
-  write32(Loc - (Config->EKind == ELF64BEKind ? 2 : 0), Instr);
+static void writeFromHalf16(uint8_t *Loc, uint32_t Insn) {
+  write32(Config->IsLE ? Loc : Loc - 2, Insn);
 }
 
-static uint32_t readInstrFromHalf16(const uint8_t *Loc) {
-  return read32(Loc - (Config->EKind == ELF64BEKind ? 2 : 0));
+static uint32_t readFromHalf16(const uint8_t *Loc) {
+  return read32(Config->IsLE ? Loc : Loc - 2);
 }
 
 PPC64::PPC64() {
@@ -361,10 +361,10 @@ void PPC64::relaxGot(uint8_t *Loc, RelType Type, uint64_t Val) const {
   case R_PPC64_TOC16_LO_DS: {
     // Convert "ld reg, .LC0@toc@l(reg)" to "addi reg, reg, var@toc@l" or
     // "addi reg, 2, var@toc".
-    uint32_t Instr = readInstrFromHalf16(Loc);
-    if (getPrimaryOpCode(Instr) != LD)
+    uint32_t Insn = readFromHalf16(Loc);
+    if (getPrimaryOpCode(Insn) != LD)
       error("expected a 'ld' for got-indirect to toc-relative relaxing");
-    writeInstrFromHalf16(Loc, (Instr & 0x03FFFFFF) | 0x38000000);
+    writeFromHalf16(Loc, (Insn & 0x03ffffff) | 0x38000000);
     relocateOne(Loc, R_PPC64_TOC16_LO, Val);
     break;
   }
@@ -391,11 +391,11 @@ void PPC64::relaxTlsGdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const {
 
   switch (Type) {
   case R_PPC64_GOT_TLSGD16_HA:
-    writeInstrFromHalf16(Loc, 0x60000000); // nop
+    writeFromHalf16(Loc, 0x60000000); // nop
     break;
   case R_PPC64_GOT_TLSGD16:
   case R_PPC64_GOT_TLSGD16_LO:
-    writeInstrFromHalf16(Loc, 0x3c6d0000); // addis r3, r13
+    writeFromHalf16(Loc, 0x3c6d0000); // addis r3, r13
     relocateOne(Loc, R_PPC64_TPREL16_HA, Val);
     break;
   case R_PPC64_TLSGD:
@@ -430,10 +430,10 @@ void PPC64::relaxTlsLdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const {
 
   switch (Type) {
   case R_PPC64_GOT_TLSLD16_HA:
-    writeInstrFromHalf16(Loc, 0x60000000); // nop
+    writeFromHalf16(Loc, 0x60000000); // nop
     break;
   case R_PPC64_GOT_TLSLD16_LO:
-    writeInstrFromHalf16(Loc, 0x3c6d0000); // addis r3, r13, 0
+    writeFromHalf16(Loc, 0x3c6d0000); // addis r3, r13, 0
     break;
   case R_PPC64_TLSLD:
     write32(Loc, 0x60000000);     // nop
@@ -757,15 +757,15 @@ void PPC64::relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const {
     checkInt(Loc, Val, 16, OriginalType);
     // DQ-form instructions use bits 28-31 as part of the instruction encoding
     // DS-form instructions only use bits 30-31.
-    uint16_t Mask = isDQFormInstruction(readInstrFromHalf16(Loc)) ? 0xF : 0x3;
+    uint16_t Mask = isDQFormInstruction(readFromHalf16(Loc)) ? 0xf : 0x3;
     checkAlignment(Loc, lo(Val), Mask + 1, OriginalType);
     write16(Loc, (read16(Loc) & Mask) | lo(Val));
   } break;
   case R_PPC64_ADDR16_HA:
   case R_PPC64_REL16_HA:
   case R_PPC64_TPREL16_HA:
     if (Config->TocOptimize && ShouldTocOptimize && ha(Val) == 0)
-      writeInstrFromHalf16(Loc, 0x60000000);
+      writeFromHalf16(Loc, 0x60000000);
     else
       write16(Loc, ha(Val));
     break;
@@ -797,35 +797,36 @@ void PPC64::relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const {
     // changed into a nop. The lo part then needs to be updated to use the
     // toc-pointer register r2, as the base register.
     if (Config->TocOptimize && ShouldTocOptimize && ha(Val) == 0) {
-      uint32_t Instr = readInstrFromHalf16(Loc);
-      if (isInstructionUpdateForm(Instr))
+      uint32_t Insn = readFromHalf16(Loc);
+      if (isInstructionUpdateForm(Insn))
         error(getErrorLocation(Loc) +
               "can't toc-optimize an update instruction: 0x" +
-              utohexstr(Instr));
-      Instr = (Instr & 0xFFE00000) | 0x00020000;
-      writeInstrFromHalf16(Loc, Instr);
+              utohexstr(Insn));
+      writeFromHalf16(Loc, (Insn & 0xffe00000) | 0x00020000 | lo(Val));
+    } else {
+      write16(Loc, lo(Val));
     }
-    write16(Loc, lo(Val));
     break;
   case R_PPC64_ADDR16_LO_DS:
   case R_PPC64_TPREL16_LO_DS: {
     // DQ-form instructions use bits 28-31 as part of the instruction encoding
     // DS-form instructions only use bits 30-31.
-    uint32_t Inst = readInstrFromHalf16(Loc);
-    uint16_t Mask = isDQFormInstruction(Inst) ? 0xF : 0x3;
+    uint32_t Insn = readFromHalf16(Loc);
+    uint16_t Mask = isDQFormInstruction(Insn) ? 0xf : 0x3;
     checkAlignment(Loc, lo(Val), Mask + 1, OriginalType);
     if (Config->TocOptimize && ShouldTocOptimize && ha(Val) == 0) {
       // When the high-adjusted part of a toc relocation evalutes to 0, it is
       // changed into a nop. The lo part then needs to be updated to use the toc
       // pointer register r2, as the base register.
-      if (isInstructionUpdateForm(Inst))
+      if (isInstructionUpdateForm(Insn))
         error(getErrorLocation(Loc) +
               "Can't toc-optimize an update instruction: 0x" +
-              Twine::utohexstr(Inst));
-      Inst = (Inst & 0xFFE0000F) | 0x00020000;
-      writeInstrFromHalf16(Loc, Inst);
+              Twine::utohexstr(Insn));
+      Insn &= 0xffe00000 | Mask;
+      writeFromHalf16(Loc, Insn | 0x00020000 | lo(Val));
+    } else {
+      write16(Loc, (read16(Loc) & Mask) | lo(Val));
     }
-    write16(Loc, (read16(Loc) & Mask) | lo(Val));
   } break;
   case R_PPC64_ADDR32:
   case R_PPC64_REL32:
@@ -934,8 +935,8 @@ void PPC64::relaxTlsGdToIe(uint8_t *Loc, RelType Type, uint64_t Val) const {
   case R_PPC64_GOT_TLSGD16_LO: {
     // Relax from addi  r3, rA, sym@got@tlsgd@l to
     //            ld r3, sym@got@tprel@l(rA)
-    uint32_t InputRegister = (readInstrFromHalf16(Loc) & (0x1f << 16));
-    writeInstrFromHalf16(Loc, 0xE8600000 | InputRegister);
+    uint32_t RA = (readFromHalf16(Loc) & (0x1f << 16));
+    writeFromHalf16(Loc, 0xe8600000 | RA);
     relocateOne(Loc, R_PPC64_GOT_TPREL16_LO_DS, Val);
     return;
   }