[PATCH] D78628: [obj2yaml] - Program headers: simplify the computation of p_filesz.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: jhenderson, MaskRay.
Herald added subscribers: hiraditya, emaste.
Herald added a reviewer: espindola.

Currently we have computations of `p_filesz` and `p_memsz` mixed together
with the use of a loop over fragments. After recent changes it is possible to
avoid using a loop for the computation of `p_filesz`, since we know that fragments
are sorted by their file offsets.

The main benefit of this change is that splits the computation of `p_filesz`
and `p_memsz` what is simpler and allows us to fix the computation of the
`p_memsz` independently (D78005 <https://reviews.llvm.org/D78005> shows the issue that we have currently).

Also it fixes the bug in program-header-size-offset.yaml.

Depends on D78627 <https://reviews.llvm.org/D78627>.


https://reviews.llvm.org/D78628

Files:
  llvm/lib/ObjectYAML/ELFEmitter.cpp
  llvm/test/tools/yaml2obj/ELF/program-header-size-offset.yaml


Index: llvm/test/tools/yaml2obj/ELF/program-header-size-offset.yaml
===================================================================
--- llvm/test/tools/yaml2obj/ELF/program-header-size-offset.yaml
+++ llvm/test/tools/yaml2obj/ELF/program-header-size-offset.yaml
@@ -30,7 +30,7 @@
 # CHECK:    MemSize: 2
 
 # CHECK:    Offset: 0x2004
-# CHECK:    FileSize: 4
+# CHECK:    FileSize: 5
 # CHECK:    MemSize: 6
 # CHECK: ]
 
Index: llvm/lib/ObjectYAML/ELFEmitter.cpp
===================================================================
--- llvm/lib/ObjectYAML/ELFEmitter.cpp
+++ llvm/lib/ObjectYAML/ELFEmitter.cpp
@@ -771,21 +771,21 @@
       PHeader.p_offset = Fragments.front().Offset;
     }
 
-    // Find the maximum offset of the end of a section in order to set p_filesz
-    // and p_memsz. When setting p_filesz, trailing SHT_NOBITS sections are not
-    // counted.
-    uint64_t FileOffset = PHeader.p_offset, MemOffset = PHeader.p_offset;
-    for (const Fragment &F : Fragments) {
-      uint64_t End = F.Offset + F.Size;
-      MemOffset = std::max(MemOffset, End);
-
-      if (F.Type != llvm::ELF::SHT_NOBITS)
-        FileOffset = std::max(FileOffset, End);
+    // Set the file size if not set explicitly.
+    if (YamlPhdr.FileSize) {
+      PHeader.p_filesz = *YamlPhdr.FileSize;
+    } else if (!Fragments.empty()) {
+      uint64_t FileSize = Fragments.back().Offset - PHeader.p_offset;
+      if (Fragments.back().Type != llvm::ELF::SHT_NOBITS)
+        FileSize += Fragments.back().Size;
+      PHeader.p_filesz = FileSize;
     }
 
-    // Set the file size and the memory size if not set explicitly.
-    PHeader.p_filesz = YamlPhdr.FileSize ? uint64_t(*YamlPhdr.FileSize)
-                                         : FileOffset - PHeader.p_offset;
+    // Find the maximum offset of the end of a section in order to set p_memsz.
+    uint64_t MemOffset = PHeader.p_offset;
+    for (const Fragment &F : Fragments)
+      MemOffset = std::max(MemOffset, F.Offset + F.Size);
+    // Set the memory size if not set explicitly.
     PHeader.p_memsz = YamlPhdr.MemSize ? uint64_t(*YamlPhdr.MemSize)
                                        : MemOffset - PHeader.p_offset;
 


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