ADCE: Remove debug info intrinsics in dead scopes

During ADCE, track which debug info scopes still have live references
from the code, and delete debug info intrinsics for the dead ones.

These intrinsics describe the locations of variables (in registers or
stack slots).  If there's no code left corresponding to a variable's
scope, then there's no way to reference the variable in the debugger and
it doesn't matter what its value is.

I add a DEBUG printout when the described location in an SSA register,
in case it helps some trying to track down why locations get lost.
However, we still delete these; the scope itself isn't attached to any
real code, so the ship has already sailed.

llvm-svn: 264800

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/test/Assembler/2010-02-05-FunctionLocalMetadataBecomesNull.ll b/llvm/test/Assembler/2010-02-05-FunctionLocalMetadataBecomesNull.ll
index 0a2462610ac..a049f18fd59 100644
--- a/llvm/test/Assembler/2010-02-05-FunctionLocalMetadataBecomesNull.ll
+++ b/llvm/test/Assembler/2010-02-05-FunctionLocalMetadataBecomesNull.ll
@@ -19,7 +19,7 @@ define i32 @main() nounwind readonly !dbg !1 {
   %v2 = ptrtoint %struct.test* %v1 to i64 ; <i64> [#uses=1]
   %v3 = sub i64 %v2, ptrtoint ([10 x %struct.test]* @TestArray to i64) ; <i64> [#uses=1]
   store i64 %v3, i64* %diff1, align 8
-  ret i32 4
+  ret i32 4, !dbg !DILocation(scope: !1)
 }
 
 declare void @llvm.dbg.declare(metadata, metadata, metadata) nounwind readnone