[lld] [llvm] [RISCV] Support RISCV Atomics ABI attributes (PR #84597)

[Paul Kirth via llvm-commits]

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@@ -1084,10 +1084,86 @@ static void mergeArch(RISCVISAInfo::OrderedExtensionMap &mergedExts,
   }
 }
 
+static void mergeAtomic(DenseMap<unsigned, unsigned> &intAttr,
+                        const InputSectionBase *oldSection,
+                        const InputSectionBase *newSection, unsigned int oldTag,
+                        unsigned int newTag) {
+  using RISCVAttrs::RISCVAtomicAbiTag::AtomicABI;
+  llvm::errs() << "oldTag=" << oldTag << ", newTag=" << newTag << "\n";
+  // Same tags stay the same, and UNKNOWN is compatible with anything
+  if (oldTag == newTag || newTag == AtomicABI::UNKNOWN)
+    return;
+
+  auto attr = RISCVAttrs::ATOMIC_ABI;
+  switch (oldTag) {
+  case AtomicABI::UNKNOWN:
+    intAttr[attr] = newTag;
+    return;
+  case AtomicABI::A6C:
+    switch (newTag) {
+    case AtomicABI::A6S:
+      intAttr[attr] = AtomicABI::A6C;
+      return;
+    case AtomicABI::A7:
+      errorOrWarn(toString(oldSection) + " has atomic_abi=" + Twine(oldTag) +
+                  " but " + toString(newSection) +
+                  " has atomic_abi=" + Twine(newTag));
+      return;
+    };
+
+  case AtomicABI::A6S:
+    switch (newTag) {
+    case AtomicABI::A6C:
+      intAttr[attr] = AtomicABI::A6C;
+      return;
+    case AtomicABI::A7:
+      intAttr[attr] = AtomicABI::A7;
+      return;
+    };
+
+  case AtomicABI::A7:
+    switch (newTag) {
+    case AtomicABI::A6S:
+      intAttr[attr] = AtomicABI::A7;
+      return;
+    case AtomicABI::A6C:
+      errorOrWarn(toString(oldSection) + " has atomic_abi=" + Twine(oldTag) +
+                  " but " + toString(newSection) +
+                  " has atomic_abi=" + Twine(newTag));
+      return;
+    };
+  default:
+    llvm_unreachable("unknown AtomicABI");
+  };
+}
+
+static void mergeX3RegUse(DenseMap<unsigned, unsigned> &intAttr,
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ilovepi wrote:

Shoot this belongs in another PR. I’ll update these in the morning. Thanks for pointing that out. 

https://github.com/llvm/llvm-project/pull/84597