[PATCH] D18911: ELF: Emit .eh_frame_hdr entries for FDEs with duplicate PCs.

[Peter Collingbourne via llvm-commits]

pcc updated this revision to Diff 53146.
pcc added a comment.

Set FDE count in .eh_frame_hdr correctly instead


http://reviews.llvm.org/D18911

Files:
  ELF/OutputSections.cpp
  test/ELF/eh-frame-hdr-icf.s

Index: test/ELF/eh-frame-hdr-icf.s
===================================================================
--- /dev/null
+++ test/ELF/eh-frame-hdr-icf.s
@@ -0,0 +1,27 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: ld.lld %t -o %t2 --icf=all --eh-frame-hdr
+# RUN: llvm-objdump -s %t2 | FileCheck %s
+
+# CHECK: Contents of section .eh_frame_hdr:
+# CHECK-NEXT: 101a0 011b033b b4ffffff 01000000 600e0000
+#                                     ^ FDE count
+# CHECK-NEXT: 101b0 e8ffffff 00000000 00000000
+#                   ^ FDE for f2
+
+.globl _start, f1, f2
+_start:
+  ret
+
+.section .text.f1, "ax"
+f1:
+  .cfi_startproc
+  ret
+  .cfi_endproc
+
+.section .text.f2, "ax"
+f2:
+  .cfi_startproc
+  ret
+  .cfi_endproc
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -733,23 +733,25 @@
 template <class ELFT> void EhFrameHeader<ELFT>::writeTo(uint8_t *Buf) {
   const endianness E = ELFT::TargetEndianness;
 
+  uintX_t EhVA = Sec->getVA();
+  uintX_t VA = this->getVA();
+
+  // InitialPC -> Offset in .eh_frame, sorted by InitialPC, and deduplicate PCs.
+  // FIXME: Deduplication leaves unneeded null bytes at the end of the section.
+  std::map<uintX_t, size_t> PcToOffset;
+  for (const FdeData &F : FdeList)
+    PcToOffset[getFdePc(EhVA, F)] = F.Off;
+
   const uint8_t Header[] = {1, DW_EH_PE_pcrel | DW_EH_PE_sdata4,
                             DW_EH_PE_udata4,
                             DW_EH_PE_datarel | DW_EH_PE_sdata4};
   memcpy(Buf, Header, sizeof(Header));
 
-  uintX_t EhVA = Sec->getVA();
-  uintX_t VA = this->getVA();
   uintX_t EhOff = EhVA - VA - 4;
   write32<E>(Buf + 4, EhOff);
-  write32<E>(Buf + 8, this->FdeList.size());
+  write32<E>(Buf + 8, PcToOffset.size());
   Buf += 12;
 
-  // InitialPC -> Offset in .eh_frame, sorted by InitialPC.
-  std::map<uintX_t, size_t> PcToOffset;
-  for (const FdeData &F : FdeList)
-    PcToOffset[getFdePc(EhVA, F)] = F.Off;
-
   for (auto &I : PcToOffset) {
     // The first four bytes are an offset to the initial PC value for the FDE.
     write32<E>(Buf, I.first - VA);


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