[Metadata] Replace undef VAMs with poison VAMs

[pedroclobo]

undef debug info can be replaced with poison debug info.

[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: Pedro Lobo (pedroclobo)

Changes

undef debug info can be replaced with poison debug info.

---

Full diff: https://github.com/llvm/llvm-project/pull/129450.diff

2 Files Affected:

• (modified) llvm/lib/IR/Metadata.cpp (+3-3)
• (modified) llvm/test/DebugInfo/X86/undef-dbg-val.ll (+1-1)

diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index e3a46840eea0e..3bd2244c5e90f 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -339,7 +339,7 @@ void ReplaceableMetadataImpl::SalvageDebugInfo(const Constant &C) {
   ValueAsMetadata *MD = I->second;
   using UseTy =
       std::pair<void *, std::pair<MetadataTracking::OwnerTy, uint64_t>>;
-  // Copy out uses and update value of Constant used by debug info metadata with undef below
+  // Copy out uses and update value of Constant used by debug info metadata with poison below
   SmallVector<UseTy, 8> Uses(MD->UseMap.begin(), MD->UseMap.end());
 
   for (const auto &Pair : Uses) {
@@ -349,7 +349,7 @@ void ReplaceableMetadataImpl::SalvageDebugInfo(const Constant &C) {
     // Check for MetadataAsValue.
     if (isa<MetadataAsValue *>(Owner)) {
       cast<MetadataAsValue *>(Owner)->handleChangedMetadata(
-          ValueAsMetadata::get(UndefValue::get(C.getType())));
+          ValueAsMetadata::get(PoisonValue::get(C.getType())));
       continue;
     }
     if (!isa<Metadata *>(Owner))
@@ -359,7 +359,7 @@ void ReplaceableMetadataImpl::SalvageDebugInfo(const Constant &C) {
       continue;
     if (isa<DINode>(OwnerMD)) {
       OwnerMD->handleChangedOperand(
-          Pair.first, ValueAsMetadata::get(UndefValue::get(C.getType())));
+          Pair.first, ValueAsMetadata::get(PoisonValue::get(C.getType())));
     }
   }
 }
diff --git a/llvm/test/DebugInfo/X86/undef-dbg-val.ll b/llvm/test/DebugInfo/X86/undef-dbg-val.ll
index 61f3776c22d5a..02b94d9112a51 100644
--- a/llvm/test/DebugInfo/X86/undef-dbg-val.ll
+++ b/llvm/test/DebugInfo/X86/undef-dbg-val.ll
@@ -1,5 +1,5 @@
 ; RUN:  opt -S -passes=globalopt --experimental-debuginfo-iterators=false <%s | FileCheck %s
-; CHECK: #dbg_value(ptr undef, 
+; CHECK: #dbg_value(ptr poison,
 ; CHECK-SAME:    [[VAR:![0-9]+]],
 ; CHECK-SAME:    !DIExpression()
 ; CHECK: [[VAR]] = !DILocalVariable(name: "_format"

[llvmbot]

@llvm/pr-subscribers-debuginfo

Author: Pedro Lobo (pedroclobo)

Changes

undef debug info can be replaced with poison debug info.

---

Full diff: https://github.com/llvm/llvm-project/pull/129450.diff

2 Files Affected:

• (modified) llvm/lib/IR/Metadata.cpp (+3-3)
• (modified) llvm/test/DebugInfo/X86/undef-dbg-val.ll (+1-1)

diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index e3a46840eea0e..3bd2244c5e90f 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -339,7 +339,7 @@ void ReplaceableMetadataImpl::SalvageDebugInfo(const Constant &C) {
   ValueAsMetadata *MD = I->second;
   using UseTy =
       std::pair<void *, std::pair<MetadataTracking::OwnerTy, uint64_t>>;
-  // Copy out uses and update value of Constant used by debug info metadata with undef below
+  // Copy out uses and update value of Constant used by debug info metadata with poison below
   SmallVector<UseTy, 8> Uses(MD->UseMap.begin(), MD->UseMap.end());
 
   for (const auto &Pair : Uses) {
@@ -349,7 +349,7 @@ void ReplaceableMetadataImpl::SalvageDebugInfo(const Constant &C) {
     // Check for MetadataAsValue.
     if (isa<MetadataAsValue *>(Owner)) {
       cast<MetadataAsValue *>(Owner)->handleChangedMetadata(
-          ValueAsMetadata::get(UndefValue::get(C.getType())));
+          ValueAsMetadata::get(PoisonValue::get(C.getType())));
       continue;
     }
     if (!isa<Metadata *>(Owner))
@@ -359,7 +359,7 @@ void ReplaceableMetadataImpl::SalvageDebugInfo(const Constant &C) {
       continue;
     if (isa<DINode>(OwnerMD)) {
       OwnerMD->handleChangedOperand(
-          Pair.first, ValueAsMetadata::get(UndefValue::get(C.getType())));
+          Pair.first, ValueAsMetadata::get(PoisonValue::get(C.getType())));
     }
   }
 }
diff --git a/llvm/test/DebugInfo/X86/undef-dbg-val.ll b/llvm/test/DebugInfo/X86/undef-dbg-val.ll
index 61f3776c22d5a..02b94d9112a51 100644
--- a/llvm/test/DebugInfo/X86/undef-dbg-val.ll
+++ b/llvm/test/DebugInfo/X86/undef-dbg-val.ll
@@ -1,5 +1,5 @@
 ; RUN:  opt -S -passes=globalopt --experimental-debuginfo-iterators=false <%s | FileCheck %s
-; CHECK: #dbg_value(ptr undef, 
+; CHECK: #dbg_value(ptr poison,
 ; CHECK-SAME:    [[VAR:![0-9]+]],
 ; CHECK-SAME:    !DIExpression()
 ; CHECK: [[VAR]] = !DILocalVariable(name: "_format"

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[github-actions]

⚠️ undef deprecator found issues in your code. ⚠️

You can test this locally with the following command:

git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef[^a-zA-Z0-9_-]|UndefValue::get)' f5f5286da3a64608b5874d70b32f955267039e1c abc138136447d78e9355064091c2a6596d58e692 llvm/lib/IR/Metadata.cpp llvm/test/DebugInfo/X86/undef-dbg-val.ll

The following files introduce new uses of undef:

• llvm/test/DebugInfo/X86/undef-dbg-val.ll

Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields undef. You should use poison values for placeholders instead.

In tests, avoid using undef and having tests that trigger undefined behavior. If you need an operand with some unimportant value, you can add a new argument to the function and use that instead.

For example, this is considered a bad practice:

define void @fn() {
  ...
  br i1 undef, ...
}

Please use the following instead:

define void @fn(i1 %cond) {
  ...
  br i1 %cond, ...
}

Please refer to the Undefined Behavior Manual for more information.

[OCHyams]

LGTM