[LoopUnswitch] Preserve make.implicit metadata for unswitched conditions

[• chenli]

Summary

This patch adds support to preserve make.implicit metadata for unswitched conditions in loop pre-header.

[mcrosier]

I'm not the proper person to review this change, but I have added Weiming who may be able to assist.

test/Transforms/LoopUnswitch/copy-metadata.ll

24

Please add a newline at the end of the test case.

[• chenli]

Updated w.r.t Chad's comments.

[sanjoy]

Please upload the diff with full context.

[• chenli]

Add full context for the diff.

[weimingz]

LGTM

lib/Transforms/Scalar/LoopUnswitch.cpp

case LLVMContext::MD_prof:
           auto NewMD =
               MDBuilder(DstInst->getParent()->getContext())
                   .createBranchWeights(cast<ConstantInt>(ValF)->getZExtValue(),
                                        cast<ConstantInt>(ValT)->getZExtValue());
           MD.second = NewMD;
         }
       }
       // fallthrough.
+    case LLVMContext::MD_make_implicit:
     case LLVMContext::MD_dbg:
       DstInst->setMetadata(MD.first, MD.second);
     }
   }
 }
 
 /// EmitPreheaderBranchOnCondition - Emit a conditional branch on two values
 /// if LIC == Val, branch to TrueDst, otherwise branch to FalseDest.  Insert the

test/Transforms/LoopUnswitch/copy-metadata.ll

+; RUN: opt < %s -loop-unswitch -S < %s 2>&1 | FileCheck %s
+
+; This test checks if unswitched condition preserve make.implicit metadata.
+
+define i32 @test(i1 %cond) {
+; CHECK: br i1 %cond, label %..split_crit_edge, label %.loop_exit.split_crit_edge, !make.implicit !0
+  br label %loop_begin
+
+loop_begin:
+; CHECK: br i1 true, label %continue, label %loop_exit, !make.implicit !0
+  br i1 %cond, label %continue, label %loop_exit, !make.implicit !0
+
+continue:
+  call void @some_func()
+  br label %loop_begin
+
+loop_exit:
+  ret i32 0
+}
+
+declare void @some_func()
+
+!0 = !{}