[llvm-branch-commits] [clang] release/19.x: [clang] Don't add DWARF debug info when assembling .s with clang-cl /Z7 (#106686) (PR #107146)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (llvmbot)

<details>
<summary>Changes</summary>

Backport fcb7b390ccd5b4cfc71f13b5e16a846f3f400c10

Requested by: @<!-- -->mstorsjo

---
Full diff: https://github.com/llvm/llvm-project/pull/107146.diff


2 Files Affected:

- (modified) clang/lib/Driver/ToolChains/Clang.cpp (+26) 
- (modified) clang/test/Driver/debug-options-as.c (+16-1) 


``````````diff
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 366b147a052bf2..8858c318aba7a1 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -8561,6 +8561,32 @@ void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
     WantDebug = !A->getOption().matches(options::OPT_g0) &&
                 !A->getOption().matches(options::OPT_ggdb0);
 
+  // If a -gdwarf argument appeared, remember it.
+  bool EmitDwarf = false;
+  if (const Arg *A = getDwarfNArg(Args))
+    EmitDwarf = checkDebugInfoOption(A, Args, D, getToolChain());
+
+  bool EmitCodeView = false;
+  if (const Arg *A = Args.getLastArg(options::OPT_gcodeview))
+    EmitCodeView = checkDebugInfoOption(A, Args, D, getToolChain());
+
+  // If the user asked for debug info but did not explicitly specify -gcodeview
+  // or -gdwarf, ask the toolchain for the default format.
+  if (!EmitCodeView && !EmitDwarf && WantDebug) {
+    switch (getToolChain().getDefaultDebugFormat()) {
+    case llvm::codegenoptions::DIF_CodeView:
+      EmitCodeView = true;
+      break;
+    case llvm::codegenoptions::DIF_DWARF:
+      EmitDwarf = true;
+      break;
+    }
+  }
+
+  // If the arguments don't imply DWARF, don't emit any debug info here.
+  if (!EmitDwarf)
+    WantDebug = false;
+
   llvm::codegenoptions::DebugInfoKind DebugInfoKind =
       llvm::codegenoptions::NoDebugInfo;
 
diff --git a/clang/test/Driver/debug-options-as.c b/clang/test/Driver/debug-options-as.c
index c83c0cb90431d3..3e1ae109711003 100644
--- a/clang/test/Driver/debug-options-as.c
+++ b/clang/test/Driver/debug-options-as.c
@@ -19,12 +19,27 @@
 // GGDB0-NOT: -debug-info-kind=
 
 // Check to make sure clang with -g on a .s file gets passed.
-// RUN: %clang -### -c -integrated-as -g -x assembler %s 2>&1 \
+// This requires a target that defaults to DWARF.
+// RUN: %clang -### --target=x86_64-linux-gnu -c -integrated-as -g -x assembler %s 2>&1 \
 // RUN:   | FileCheck %s
 //
 // CHECK: "-cc1as"
 // CHECK: "-debug-info-kind=constructor"
 
+// Check that a plain -g, without any -gdwarf, for a MSVC target, doesn't
+// trigger producing DWARF output.
+// RUN: %clang -### --target=x86_64-windows-msvc -c -integrated-as -g -x assembler %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=MSVC %s
+//
+// MSVC: "-cc1as"
+// MSVC-NOT: "-debug-info-kind=constructor"
+
+// Check that clang-cl with the -Z7 option works the same, not triggering
+// any DWARF output.
+//
+// RUN: %clang_cl -### -c -Z7 -x assembler %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=MSVC %s
+
 // Check to make sure clang with -g on a .s file gets passed -dwarf-debug-producer.
 // RUN: %clang -### -c -integrated-as -g -x assembler %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=P %s

``````````

</details>


https://github.com/llvm/llvm-project/pull/107146