[Driver] Honor "-gdwarf-N" at any position for assembler sources

This fixes an issue when "-gdwarf-N" switch was ignored if it was given
before another debug option.

Differential Revision: https://reviews.llvm.org/D96865

Author: igorkudrin

clang/lib/Driver/ToolChains/Clang.cpp

@@ -981,6 +981,14 @@ static unsigned DwarfVersionNum(StringRef ArgValue) {
       .Default(0);
 }
 
+// Find a DWARF format version option.
+// This function is a complementary for DwarfVersionNum().
+static const Arg *getDwarfNArg(const ArgList &Args) {
+  return Args.getLastArg(options::OPT_gdwarf_2, options::OPT_gdwarf_3,
+                         options::OPT_gdwarf_4, options::OPT_gdwarf_5,
+                         options::OPT_gdwarf);
+}
+
 static void RenderDebugEnablingArgs(const ArgList &Args, ArgStringList &CmdArgs,
                                     codegenoptions::DebugInfoKind DebugInfoKind,
                                     unsigned DwarfVersion,
@@ -3848,9 +3856,7 @@ static void renderDebugOptions(const ToolChain &TC, const Driver &D,
   }
 
   // If a -gdwarf argument appeared, remember it.
-  const Arg *GDwarfN = Args.getLastArg(
-      options::OPT_gdwarf_2, options::OPT_gdwarf_3, options::OPT_gdwarf_4,
-      options::OPT_gdwarf_5, options::OPT_gdwarf);
+  const Arg *GDwarfN = getDwarfNArg(Args);
   bool EmitDwarf = false;
   if (GDwarfN) {
     if (checkDebugInfoOption(GDwarfN, Args, D, TC))
@@ -7168,18 +7174,14 @@ void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
   // Forward -g and handle debug info related flags, assuming we are dealing
   // with an actual assembly file.
   bool WantDebug = false;
-  unsigned DwarfVersion = 0;
   Args.ClaimAllArgs(options::OPT_g_Group);
-  if (Arg *A = Args.getLastArg(options::OPT_g_Group)) {
+  if (Arg *A = Args.getLastArg(options::OPT_g_Group))
     WantDebug = !A->getOption().matches(options::OPT_g0) &&
                 !A->getOption().matches(options::OPT_ggdb0);
-    if (WantDebug)
-      DwarfVersion = DwarfVersionNum(A->getSpelling());
-  }
 
-  unsigned DefaultDwarfVersion = ParseDebugDefaultVersion(getToolChain(), Args);
-  if (DwarfVersion == 0)
-    DwarfVersion = DefaultDwarfVersion;
+  unsigned DwarfVersion = ParseDebugDefaultVersion(getToolChain(), Args);
+  if (const Arg *GDwarfN = getDwarfNArg(Args))
+    DwarfVersion = DwarfVersionNum(GDwarfN->getSpelling());
 
   if (DwarfVersion == 0)
     DwarfVersion = getToolChain().GetDefaultDwarfVersion();

clang/test/Driver/debug-options-as.c

@@ -60,3 +60,18 @@
 // GDWARF64_VER:  error: invalid argument '-gdwarf64' only allowed with 'DWARFv3 or greater'
 // GDWARF64_32ARCH: error: invalid argument '-gdwarf64' only allowed with '64 bit architecture'
 // GDWARF64_ELF: error: invalid argument '-gdwarf64' only allowed with 'ELF platforms'
+
+// Check that -gdwarf-N can be placed before other options of the "-g" group.
+// RUN: %clang -### -c -g -gdwarf-3 -target %itanium_abi_triple -fintegrated-as -x assembler %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=DWARF3 %s
+// RUN: %clang -### -c -gdwarf-3 -g -target %itanium_abi_triple -fintegrated-as -x assembler %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=DWARF3 %s
+// RUN: %clang -### -c -g -gdwarf-5 -target %itanium_abi_triple -fintegrated-as -x assembler %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=DWARF5 %s
+// RUN: %clang -### -c -gdwarf-5 -g -target %itanium_abi_triple -fintegrated-as -x assembler %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=DWARF5 %s
+
+// DWARF3: "-cc1as"
+// DWARF3: "-dwarf-version=3"
+// DWARF5: "-cc1as"
+// DWARF5: "-dwarf-version=5"