[llvm][AsmWriter] Don't skip zero-valued DwarfEnum MDField when ShouldSkipZero is not set

[Michael137]

I ran into this while working on a different patch where I'm emitting a zero-valued DWARF enum field which shouldn't be skipped.

This patch checks the (currently unused) ShouldSkipZero before deciding to skip printing this field. Based on git history this seems like an oversight from the initial refactor that introduced this. We have a similar check in printInt.

Wasn't sure how to best test this, but tests in an upcoming patch rely on this functionality (see #126045).

Currently the only place ShouldSkipZero is set to false is when emitting the DW_LANG_ enum. But the language codes start at 0x1. So it never exercised this codepath (and we should probably just make it not pass this parameter).

[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: Michael Buch (Michael137)

Changes

I ran into this whil working on a different patch where I'm emitting a zero-valued DWARF enum field which shouldn't be skipped.

This patch checks the (currently unused) ShouldSkipZero before deciding to skip printing this field. Based on git history this seems like an oversight from the initial refactor that introduced this. We have a similar check in printInt.

Wasn't sure how to best test this, but tests in an upcoming patch rely on this functionality.

Currently the only place ShouldSkipZero is set to false is when emitting the DW_LANG_ enum. But the language codes start at 0x1. So it never exercised this codepath (and we should probably just make it not pass this parameter).

---

Full diff: https://github.com/llvm/llvm-project/pull/126044.diff

1 Files Affected:

• (modified) llvm/lib/IR/AsmWriter.cpp (+1-1)

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index c8ed4e19f1b612..57e9cccdc0fb6e 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -2004,7 +2004,7 @@ void MDFieldPrinter::printNameTableKind(StringRef Name,
 template <class IntTy, class Stringifier>
 void MDFieldPrinter::printDwarfEnum(StringRef Name, IntTy Value,
                                     Stringifier toString, bool ShouldSkipZero) {
-  if (!Value)
+  if (ShouldSkipZero && !Value)
     return;
 
   Out << FS << Name << ": ";