[ELF] Add TargetInfo::adjustGotPcExpr for `R_GOT_PC` relaxations. NFC

With this change, `TargetInfo::adjustRelaxExpr` is only related to TLS
relaxations and a subsequent clean-up can delete the `data` parameter.

Differential Revision: https://reviews.llvm.org/D92079

lld/ELF/Arch/PPC64.cpp

@@ -384,6 +384,8 @@ public:
   bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override;
   RelExpr adjustRelaxExpr(RelType type, const uint8_t *data,
                           RelExpr expr) const override;
+  RelExpr adjustGotPcExpr(RelType type, int64_t addend,
+                          const uint8_t *loc) const override;
   void relaxGot(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
   void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
@@ -1392,15 +1394,6 @@ bool PPC64::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
 
 RelExpr PPC64::adjustRelaxExpr(RelType type, const uint8_t *data,
                                RelExpr expr) const {
-  if ((type == R_PPC64_GOT_PCREL34 || type == R_PPC64_PCREL_OPT) &&
-      config->pcRelOptimize) {
-    // It only makes sense to optimize pld since paddi means that the address
-    // of the object in the GOT is required rather than the object itself.
-    assert(data && "Expecting an instruction encoding here");
-    if ((readPrefixedInstruction(data) & 0xfc000000) == 0xe4000000)
-      return R_PPC64_RELAX_GOT_PC;
-  }
-
   if (type != R_PPC64_GOT_TLSGD_PCREL34 && expr == R_RELAX_TLS_GD_TO_IE)
     return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
   if (expr == R_RELAX_TLS_LD_TO_LE)
@@ -1408,6 +1401,18 @@ RelExpr PPC64::adjustRelaxExpr(RelType type, const uint8_t *data,
   return expr;
 }
 
+RelExpr PPC64::adjustGotPcExpr(RelType type, int64_t addend,
+                               const uint8_t *loc) const {
+  if ((type == R_PPC64_GOT_PCREL34 || type == R_PPC64_PCREL_OPT) &&
+      config->pcRelOptimize) {
+    // It only makes sense to optimize pld since paddi means that the address
+    // of the object in the GOT is required rather than the object itself.
+    if ((readPrefixedInstruction(loc) & 0xfc000000) == 0xe4000000)
+      return R_PPC64_RELAX_GOT_PC;
+  }
+  return R_GOT_PC;
+}
+
 // Reference: 3.7.4.1 of the 64-bit ELF V2 abi supplement.
 // The general dynamic code sequence for a global `x` uses 4 instructions.
 // Instruction                    Relocation                Symbol

lld/ELF/Arch/X86_64.cpp

@@ -40,8 +40,8 @@ public:
   void applyJumpInstrMod(uint8_t *loc, JumpModType type,
                          unsigned size) const override;
 
-  RelExpr adjustRelaxExpr(RelType type, const uint8_t *data,
-                          RelExpr expr) const override;
+  RelExpr adjustGotPcExpr(RelType type, int64_t addend,
+                          const uint8_t *loc) const override;
   void relaxGot(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
   void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
@@ -728,12 +728,12 @@ void X86_64::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
   }
 }
 
-RelExpr X86_64::adjustRelaxExpr(RelType type, const uint8_t *data,
-                                RelExpr relExpr) const {
+RelExpr X86_64::adjustGotPcExpr(RelType type, int64_t addend,
+                                const uint8_t *loc) const {
   if (type != R_X86_64_GOTPCRELX && type != R_X86_64_REX_GOTPCRELX)
-    return relExpr;
-  const uint8_t op = data[-2];
-  const uint8_t modRm = data[-1];
+    return R_GOT_PC;
+  const uint8_t op = loc[-2];
+  const uint8_t modRm = loc[-1];
 
   // FIXME: When PIC is disabled and foo is defined locally in the
   // lower 32 bit address space, memory operand in mov can be converted into
@@ -748,11 +748,11 @@ RelExpr X86_64::adjustRelaxExpr(RelType type, const uint8_t *data,
 
   // We don't support test/binop instructions without a REX prefix.
   if (type == R_X86_64_GOTPCRELX)
-    return relExpr;
+    return R_GOT_PC;
 
   // Relaxation of test, adc, add, and, cmp, or, sbb, sub, xor.
   // If PIC then no relaxation is available.
-  return config->isPic ? relExpr : R_RELAX_GOT_PC_NOPIC;
+  return config->isPic ? R_GOT_PC : R_RELAX_GOT_PC_NOPIC;
 }
 
 // A subset of relaxations can only be applied for no-PIC. This method

lld/ELF/Relocations.cpp

@@ -1361,9 +1361,7 @@ static void scanReloc(InputSectionBase &sec, OffsetGetter &getOffset, RelTy *&i,
   // runtime, because the main executable is always at the beginning of a search
   // list. We can leverage that fact.
   if (!sym.isPreemptible && (!sym.isGnuIFunc() || config->zIfuncNoplt)) {
-    if (expr == R_GOT_PC && !isAbsoluteValue(sym)) {
-      expr = target->adjustRelaxExpr(type, relocatedAddr, expr);
-    } else {
+    if (expr != R_GOT_PC) {
       // The 0x8000 bit of r_addend of R_PPC_PLTREL24 is used to choose call
       // stub type. It should be ignored if optimized to R_PC.
       if (config->emachine == EM_PPC && expr == R_PPC32_PLTREL)
@@ -1375,6 +1373,8 @@ static void scanReloc(InputSectionBase &sec, OffsetGetter &getOffset, RelTy *&i,
             type == R_HEX_GD_PLT_B22_PCREL_X ||
             type == R_HEX_GD_PLT_B32_PCREL_X)))
       expr = fromPlt(expr);
+    } else if (!isAbsoluteValue(sym)) {
+      expr = target->adjustGotPcExpr(type, addend, relocatedAddr);
     }
   }
 

lld/ELF/Target.cpp

@@ -155,6 +155,11 @@ RelExpr TargetInfo::adjustRelaxExpr(RelType type, const uint8_t *data,
   return expr;
 }
 
+RelExpr TargetInfo::adjustGotPcExpr(RelType type, int64_t addend,
+                                    const uint8_t *data) const {
+  return R_GOT_PC;
+}
+
 void TargetInfo::relaxGot(uint8_t *loc, const Relocation &rel,
                           uint64_t val) const {
   llvm_unreachable("Should not have claimed to be relaxable");

lld/ELF/Target.h

@@ -150,6 +150,8 @@ public:
 
   virtual RelExpr adjustRelaxExpr(RelType type, const uint8_t *data,
                                   RelExpr expr) const;
+  virtual RelExpr adjustGotPcExpr(RelType type, int64_t addend,
+                                  const uint8_t *loc) const;
   virtual void relaxGot(uint8_t *loc, const Relocation &rel,
                         uint64_t val) const;
   virtual void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,