[InstCombine] Preserve !annotation for newly created instructions.

[fhahn]

Summary

When replacing an instruction with !annotation with a newly created
replacement, add the !annotation metadata to the replacement.

This mostly covers cases where the new instructions are created using
the ::Create helpers. Instructions created by IRBuilder will be handled
by D91444.

[thegameg]

LGTM

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

#endif
 
     if (Instruction *Result = visit(*I)) {
       ++NumCombined;
       // Should we replace the old instruction with a new one?
       if (Result != I) {
         LLVM_DEBUG(dbgs() << "IC: Old = " << *I << '\n'
                           << "    New = " << *Result << '\n');
 
-        if (I->getDebugLoc())
-          Result->setDebugLoc(I->getDebugLoc());
+        Result->copyMetadata(*I,
+                             {LLVMContext::MD_dbg, LLVMContext::MD_annotation});
         // Everything uses the new instruction now.
         I->replaceAllUsesWith(Result);
 
         // Move the name to the new instruction first.
         Result->takeName(I);
 
         // Insert the new instruction into the basic block...
         BasicBlock *InstParent = I->getParent();

llvm/test/Transforms/InstCombine/annotations.ll

 ; RUN: opt < %s -instcombine -S | FileCheck --match-full-lines %s
 
 ; Test cases to make sure !annotation metadata is preserved, if possible.
 ; Currently we fail to preserve !annotation metadata in many cases.
 
 ; Make sure !annotation metadata is added to new instructions, if the source
 ; instruction has !annotation metadata.
 define i1 @fold_to_new_instruction(i8* %a, i8* %b) {
 ; CHECK-LABEL: define {{.+}} @fold_to_new_instruction({{.+}}
-; CHECK-NEXT:    [[C:%.*]] = icmp uge i8* [[A:%.*]], [[B:%[a-z]*]]
+; CHECK-NEXT:    [[C:%.*]] = icmp uge i8* [[A:%.*]], [[B:%[a-z]*]], !annotation [[ANN:![0-9]+]]
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
   %a.c = bitcast i8* %a to i32*, !annotation !0
   %b.c = bitcast i8* %b to i32*, !annotation !0
   %c = icmp uge i32* %a.c, %b.c, !annotation !0
   ret i1 %c
 }