[llvm-branch-commits] [llvm] RuntimeLibcalls: Remove the dead IsDefault emitter machinery (PR #219947)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-tablegen

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

The IsDefault bit on RuntimeLibcallImpl fed a LibCallToDefaultImpl map in the
TableGen backend that was populated but never read.

Co-authored-by: Claude (Claude-Opus-4.8) <noreply@<!-- -->anthropic.com>

---
Full diff: https://github.com/llvm/llvm-project/pull/219947.diff


3 Files Affected:

- (modified) llvm/test/TableGen/RuntimeLibcallEmitter.td (+5-8) 
- (modified) llvm/utils/TableGen/Basic/RuntimeLibcalls.cpp (-8) 
- (modified) llvm/utils/TableGen/Basic/RuntimeLibcalls.h (-5) 


``````````diff
diff --git a/llvm/test/TableGen/RuntimeLibcallEmitter.td b/llvm/test/TableGen/RuntimeLibcallEmitter.td
index 51c3e02885f4b..35e0068304e5e 100644
--- a/llvm/test/TableGen/RuntimeLibcallEmitter.td
+++ b/llvm/test/TableGen/RuntimeLibcallEmitter.td
@@ -13,14 +13,11 @@ def MEMCPY : RuntimeLibcall;
 def MEMSET : RuntimeLibcall;
 def CALLOC : RuntimeLibcall;
 
-// Test default names.
-let IsDefault = true in {
-  def __ashlsi3 : RuntimeLibcallImpl<SHL_I32>;
-  def __lshrdi3 : RuntimeLibcallImpl<SRL_I64>;
-
-  def sqrtl_f128 : RuntimeLibcallImpl<SQRT_F128, "sqrtl">;
-  def sqrtl_f80 : RuntimeLibcallImpl<SQRT_F80, "sqrtl">;
-}
+def __ashlsi3 : RuntimeLibcallImpl<SHL_I32>;
+def __lshrdi3 : RuntimeLibcallImpl<SRL_I64>;
+
+def sqrtl_f128 : RuntimeLibcallImpl<SQRT_F128, "sqrtl">;
+def sqrtl_f80 : RuntimeLibcallImpl<SQRT_F80, "sqrtl">;
 
 // Ignore non-default in initDefaultLibCallNames.
 def bzero : RuntimeLibcallImpl<BZERO>;
diff --git a/llvm/utils/TableGen/Basic/RuntimeLibcalls.cpp b/llvm/utils/TableGen/Basic/RuntimeLibcalls.cpp
index 9c4a9107a6849..dfccfca5dbb4d 100644
--- a/llvm/utils/TableGen/Basic/RuntimeLibcalls.cpp
+++ b/llvm/utils/TableGen/Basic/RuntimeLibcalls.cpp
@@ -69,14 +69,6 @@ RuntimeLibcalls::RuntimeLibcalls(const RecordKeeper &Records) {
 
     const RuntimeLibcallImpl &LibCallImpl = RuntimeLibcallImplDefList.back();
     Def2RuntimeLibcallImpl[LibCallImplDef] = &LibCallImpl;
-
-    if (LibCallImpl.isDefault()) {
-      const RuntimeLibcall *Provides = LibCallImpl.getProvides();
-      if (!Provides)
-        PrintFatalError(LibCallImplDef->getLoc(),
-                        "default implementations must provide a libcall");
-      LibCallToDefaultImpl[Provides] = &LibCallImpl;
-    }
   }
 }
 
diff --git a/llvm/utils/TableGen/Basic/RuntimeLibcalls.h b/llvm/utils/TableGen/Basic/RuntimeLibcalls.h
index 787c6b0d6a360..b296c86ffd111 100644
--- a/llvm/utils/TableGen/Basic/RuntimeLibcalls.h
+++ b/llvm/utils/TableGen/Basic/RuntimeLibcalls.h
@@ -135,8 +135,6 @@ class RuntimeLibcallImpl {
     OS << '\"' << getLibcallFuncName() << '\"';
   }
 
-  bool isDefault() const { return TheDef->getValueAsBit("IsDefault"); }
-
   void emitEnumEntry(raw_ostream &OS) const {
     OS << "RTLIB::impl_" << this->getName();
   }
@@ -173,9 +171,6 @@ class RuntimeLibcalls {
   std::vector<RuntimeLibcall> RuntimeLibcallDefList;
   std::vector<RuntimeLibcallImpl> RuntimeLibcallImplDefList;
 
-  DenseMap<const RuntimeLibcall *, const RuntimeLibcallImpl *>
-      LibCallToDefaultImpl;
-
 public:
   RuntimeLibcalls(const RecordKeeper &Records);
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/219947