ThinLTOBitcodeWriter: Do not rewrite intrinsic functions when splitting modules.

[pcc]

Summary

Changing the type of an intrinsic may invalidate the IR.

[tejohnson]

LGTM

llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp

145 ↗

(On Diff #107213)

Suggest adding a comment.

llvm/trunk/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp

void simplifyExternals(Module &M) {
 
   for (auto I = M.begin(), E = M.end(); I != E;) {
     Function &F = *I++;
     if (F.isDeclaration() && F.use_empty()) {
       F.eraseFromParent();
       continue;
     }
 
-    if (!F.isDeclaration() || F.getFunctionType() == EmptyFT)
+    if (!F.isDeclaration() || F.getFunctionType() == EmptyFT ||
+        // Changing the type of an intrinsic may invalidate the IR.
+        F.getName().startswith("llvm."))
       continue;
 
     Function *NewF =
         Function::Create(EmptyFT, GlobalValue::ExternalLinkage, "", &M);
     NewF->setVisibility(F.getVisibility());
     NewF->takeName(&F);
     F.replaceAllUsesWith(ConstantExpr::getBitCast(NewF, F.getType()));
     F.eraseFromParent();

llvm/trunk/test/Transforms/ThinLTOBitcodeWriter/split-vfunc.ll

 ; M1: define available_externally i64 @ok1
 define i64 @ok1(i8* %this) {
   ret i64 42
 }
 
 ; M0: define i64 @ok2
 ; M1: define available_externally i64 @ok2
 define i64 @ok2(i8* %this, i64 %arg) {
+  %1 = tail call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %arg, i64 %arg)
   ret i64 %arg
 }
 
+; M1: declare { i64, i1 } @llvm.sadd.with.overflow.i64(i64, i64)
+declare { i64, i1 } @llvm.sadd.with.overflow.i64(i64, i64)
+
 ; M0: define void @wrongtype1
 ; M1: declare void @wrongtype1()
 define void @wrongtype1(i8*) {
   ret void
 }
 
 ; M0: define i128 @wrongtype2
 ; M1: declare void @wrongtype2()