[PATCH] D133875: [clang] fix generation of .debug_aranges with LTO (resubmit)

[Azat Khuzhin via Phabricator via cfe-commits]

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Right now in case of LTO the section is not emited:

  $ cat test.c
  void __attribute__((optnone)) bar()
  {
  }
  void __attribute__((optnone)) foo()
  {
          bar();
  }
  int main()
  {
          foo();
  }
  
  $ clang -flto=thin -gdwarf-aranges -g -O3 test.c
  $ eu-readelf -waranges a.out  | fgrep -c -e foo -e bar
  0
  
  $ clang -gdwarf-aranges -g -O3 test.c
  $ eu-readelf -waranges a.out  | fgrep -c -e foo -e bar
  2

Fix this by passing explicitly -mllvm -generate-arange-section.

But as mentioned by @dblaikie:

  the better solution would be to encode this in IR metadata
  (DICompileUnit) if it's reasonable to respect this option on a per-CU
  basis (which it probably is, though that'd be a bit of backend work) -
  or to set it as IR global metadata (like how the DWARF version is
  encoded - probably using the same IR linker merging strategy, of
  choosing the highest value (so if any module has aranges, then a linked
  module has aranges too - even for the CUs that had it turned off) if
  it's really not feasible to support on a per-CU basis) but probably
  OK-enough, given that aranges is hopefully on the way out & not worth
  all the work of the deeper fix

This is the resubmit, previous submission [1], got reverted, due to test
failures, that had been addressed in [2] and [3].

  [1]: https://reviews.llvm.org/D133092
  [3]: https://reviews.llvm.org/D133841
  [4]: https://reviews.llvm.org/D133847

Signed-off-by: Azat Khuzhin <a.khuzhin at semrush.com>
Suggested-by: OCHyams <orlando.hyams at sony.com>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133875

Files:
  clang/lib/Driver/ToolChains/CommonArgs.cpp
  clang/test/Driver/debug-options-lld.c


Index: clang/test/Driver/debug-options-lld.c
===================================================================
--- /dev/null
+++ clang/test/Driver/debug-options-lld.c
@@ -0,0 +1,12 @@
+// REQUIRES: lld
+// Check that lld will emit dwarf aranges.
+
+// RUN: %clang -### -target x86_64-unknown-linux -c -gdwarf-aranges %s 2>&1 | FileCheck -check-prefix=GARANGE %s
+// RUN: %clang -### -target x86_64-unknown-linux -flto -gdwarf-aranges %s 2>&1 | FileCheck -check-prefix=LDGARANGE %s
+// RUN: %clang -### -target x86_64-unknown-linux -flto=thin -gdwarf-aranges %s 2>&1 | FileCheck -check-prefix=LDGARANGE %s
+// RUN: %clang -### -target x86_64-unknown-linux -fuse-ld=lld -flto -gdwarf-aranges %s 2>&1 | FileCheck -check-prefix=LLDGARANGE %s
+// RUN: %clang -### -target x86_64-unknown-linux -fuse-ld=lld -flto=thin -gdwarf-aranges %s 2>&1 | FileCheck -check-prefix=LLDGARANGE %s
+//
+// GARANGE-DAG: -generate-arange-section
+// LDGARANGE-NOT: {{"[^"]*lld[^"]*"}} {{.*}} "-generate-arange-section"
+// LLDGARANGE: {{"[^"]*lld[^"]*"}} {{.*}} "-generate-arange-section"
Index: clang/lib/Driver/ToolChains/CommonArgs.cpp
===================================================================
--- clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -506,6 +506,19 @@
             Suffix,
         Plugin);
     CmdArgs.push_back(Args.MakeArgString(Plugin));
+  } else {
+    // NOTE:
+    // - it is not possible to use lld for PS4
+    // - addLTOOptions() is not used for PS5
+    // Hence no need to handle SCE (like in Clang.cpp::renderDebugOptions()).
+    //
+    // But note, this solution is far from perfect, better to encode it into IR
+    // metadata, but this may not be worth it, since it looks like aranges is
+    // on the way out.
+    if (Args.hasArg(options::OPT_gdwarf_aranges)) {
+      CmdArgs.push_back(Args.MakeArgString("-mllvm"));
+      CmdArgs.push_back(Args.MakeArgString("-generate-arange-section"));
+    }
   }
 
   // Try to pass driver level flags relevant to LTO code generation down to


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