[ELF] Remove zero-value DT_JMPREL when IPLT is present while PLT isn't

The zero-value DT_JMPREL is benign but not needed.
This is also code simplification available after https://reviews.llvm.org/D65651

Author: MaskRay

lld/ELF/SyntheticSections.cpp

@@ -1285,13 +1285,7 @@ static uint64_t addRelaSz(const RelocationBaseSection &relaDyn) {
 // output section. When this occurs we cannot just use the OutputSection
 // Size. Moreover the [DT_JMPREL, DT_JMPREL + DT_PLTRELSZ) is permitted to
 // overlap with the [DT_RELA, DT_RELA + DT_RELASZ).
-static uint64_t addPltRelSz() {
-  size_t size = in.relaPlt->getSize();
-  if (in.relaIplt->getParent() == in.relaPlt->getParent() &&
-      in.relaIplt->name == in.relaPlt->name)
-    size += in.relaIplt->getSize();
-  return size;
-}
+static uint64_t addPltRelSz() { return in.relaPlt->getSize(); }
 
 // Add remaining entries to complete .dynamic contents.
 template <class ELFT>
@@ -1407,13 +1401,7 @@ DynamicSection<ELFT>::computeContents() {
     addInt(config->useAndroidRelrTags ? DT_ANDROID_RELRENT : DT_RELRENT,
            sizeof(Elf_Relr));
   }
-  // .rel[a].plt section usually consists of two parts, containing plt and
-  // iplt relocations. It is possible to have only iplt relocations in the
-  // output. In that case relaPlt is empty and have zero offset, the same offset
-  // as relaIplt has. And we still want to emit proper dynamic tags for that
-  // case, so here we always use relaPlt as marker for the beginning of
-  // .rel[a].plt section.
-  if (isMain && (in.relaPlt->isNeeded() || in.relaIplt->isNeeded())) {
+  if (isMain && in.relaPlt->isNeeded()) {
     addInSec(DT_JMPREL, *in.relaPlt);
     entries.emplace_back(DT_PLTRELSZ, addPltRelSz());
     switch (config->emachine) {

lld/test/ELF/aarch64-gnu-ifunc-nonpreemptable.s

@@ -65,14 +65,14 @@ main:
 # PIE-EMPTY:
 # PIE-NEXT: <myfunc>:
 # PIE-NEXT:    10270: adrp    x16, 0x30000
-# PIE-NEXT:    10274: ldr     x17, [x16, #896]
-# PIE-NEXT:    10278: add     x16, x16, #896
-# PIE-NEXT:    1027c: br      x17
+# PIE-NEXT:           ldr     x17, [x16, #832]
+# PIE-NEXT:           add     x16, x16, #832
+# PIE-NEXT:           br      x17
 
 # PIE-RELOC:      .rela.dyn {
-# PIE-RELOC-NEXT:   0x30380 R_AARCH64_IRELATIVE - 0x10260
+# PIE-RELOC-NEXT:   0x30340 R_AARCH64_IRELATIVE - 0x10260
 # PIE-RELOC-NEXT: }
 # PIE-RELOC:      Hex dump of section '.got.plt':
-# NO-APPLY:       0x00030380 00000000 00000000
-# APPLY:          0x00030380 60020100 00000000
+# NO-APPLY:       0x00030340 00000000 00000000
+# APPLY:          0x00030340 60020100 00000000
 # PIE-RELOC-EMPTY:

lld/test/ELF/gnu-ifunc-dyntags.s

@@ -9,15 +9,13 @@
 
 # CHECK:  Name          Size   VMA
 # CHECK:  .rela.dyn   00000030 0000000000000248
-# CHECK:  .got.plt    00000010 00000000000033b0
+# CHECK:  .got.plt    00000010 0000000000003370
 
 # TAGS:   Tag                Type                 Name/Value
 # TAGS:   0x0000000000000007 RELA                 0x248
 # TAGS:   0x0000000000000008 RELASZ               48 (bytes)
-# TAGS:   0x0000000000000017 JMPREL               0x0
-# TAGS:   0x0000000000000002 PLTRELSZ             0 (bytes)
-# TAGS:   0x0000000000000003 PLTGOT               0x33B0
-# TAGS:   0x0000000000000014 PLTREL               RELA
+# TAGS-NOT: JMPREL
+# TAGS-NOT: PLTREL
 
 # TAGS:      Relocations [
 # TAGS-NEXT:   Section {{.*}} .rela.dyn {

lld/test/ELF/ppc32-ifunc-nonpreemptible-pic.s

@@ -10,16 +10,16 @@
 # RUN: llvm-readelf -x .got2 %t | FileCheck --check-prefix=HEX2 %s
 
 # RELOC:      .rela.dyn {
-# RELOC-NEXT:   0x3024C R_PPC_RELATIVE - 0x101A0
-# RELOC-NEXT:   0x30250 R_PPC_IRELATIVE - 0x10188
+# RELOC-NEXT:   0x3022C R_PPC_RELATIVE - 0x101A0
+# RELOC-NEXT:   0x30230 R_PPC_IRELATIVE - 0x10188
 # RELOC-NEXT: }
 
 # SYM: 000101a0 0 FUNC GLOBAL DEFAULT {{.*}} func
 # HEX:      Hex dump of section '.got2':
-# HEX-NEXT: 0x0003024c 00000000 ....
+# HEX-NEXT: 0x0003022c 00000000 ....
 
 # HEX2:      Hex dump of section '.got2':
-# HEX2-NEXT: 0x0003024c 000101a0 ....
+# HEX2-NEXT: 0x0003022c 000101a0 ....
 
 .section .got2,"aw"
 .long func

lld/test/ELF/riscv-ifunc-nonpreemptible.s

@@ -16,11 +16,11 @@
 # RUN: llvm-objdump -d --no-show-raw-insn %t.64 | FileCheck --check-prefix=DIS64 %s
 
 # RELOC32:      .rela.dyn {
-# RELOC32-NEXT:   0x3220 R_RISCV_IRELATIVE - 0x117C
+# RELOC32-NEXT:   0x3200 R_RISCV_IRELATIVE - 0x117C
 # RELOC32-NEXT: }
 # RELOC32-LABEL:    Hex dump of section '.got.plt':
-# NO-APPLY-RELOC32: 0x00003220 00000000
-# APPLY-RELOC32:    0x00003220 7c110000
+# NO-APPLY-RELOC32: 0x00003200 00000000
+# APPLY-RELOC32:    0x00003200 7c110000
 # RELOC32-EMPTY:
 
 # SYM32: 0001190 0 FUNC GLOBAL DEFAULT {{.*}} func
@@ -30,18 +30,18 @@
 # DIS32-NEXT:       addi a0, a0, 0x10
 # DIS32:      Disassembly of section .iplt:
 # DIS32:      <func>:
-## 32-bit: &.got.plt[func]-. = 0x3220-0x1190 = 4096*2+144
+## 32-bit: &.got.plt[func]-. = 0x3200-0x1190 = 4096*2+0x70
 # DIS32-NEXT: 1190: auipc t3, 0x2
-# DIS32-NEXT:       lw t3, 0x90(t3)
+# DIS32-NEXT:       lw t3, 0x70(t3)
 # DIS32-NEXT:       jalr t1, t3
 # DIS32-NEXT:       nop
 
 # RELOC64:      .rela.dyn {
-# RELOC64-NEXT:   0x3380 R_RISCV_IRELATIVE - 0x1260
+# RELOC64-NEXT:   0x3340 R_RISCV_IRELATIVE - 0x1260
 # RELOC64-NEXT: }
 # RELOC64-LABEL:    Hex dump of section '.got.plt':
-# NO-APPLY-RELOC64: 0x00003380 00000000 00000000
-# APPLY-RELOC64:    0x00003380 60120000 00000000
+# NO-APPLY-RELOC64: 0x00003340 00000000 00000000
+# APPLY-RELOC64:    0x00003340 60120000 00000000
 # RELOC64-EMPTY:
 
 # SYM64: 000000000001270 0 FUNC GLOBAL DEFAULT {{.*}} func
@@ -51,9 +51,9 @@
 # DIS64-NEXT:       addi a0, a0, 0xc
 # DIS64:      Disassembly of section .iplt:
 # DIS64:      <func>:
-## 64-bit: &.got.plt[func]-. = 0x3380-0x1270 = 4096*2+272
+## 64-bit: &.got.plt[func]-. = 0x3340-0x1270 = 4096*2+0xd0
 # DIS64-NEXT: 1270: auipc t3, 0x2
-# DIS64-NEXT:       ld t3, 0x110(t3)
+# DIS64-NEXT:       ld t3, 0xd0(t3)
 # DIS64-NEXT:       jalr t1, t3
 # DIS64-NEXT:       nop