Merge pull request swiftlang#39059 from eeckstein/fix-perf-regressions

COWOpts: handle debug_value instructions

Author: eeckstein

lib/SILOptimizer/Transforms/COWOpts.cpp

@@ -247,6 +247,7 @@ void COWOptsPass::collectEscapePoints(SILValue v,
       case SILInstructionKind::BeginCOWMutationInst:
       case SILInstructionKind::RefElementAddrInst:
       case SILInstructionKind::RefTailAddrInst:
+      case SILInstructionKind::DebugValueInst:
         break;
       case SILInstructionKind::BranchInst:
         collectEscapePoints(cast<BranchInst>(user)->getArgForOperand(use),

test/SILOptimizer/cow_opts.sil

@@ -36,6 +36,7 @@ sil @test_simple : $@convention(thin) (@owned Buffer) -> (Int, Builtin.Int1, @ow
 bb0(%0 : $Buffer):
   %e = end_cow_mutation %0 : $Buffer
   %addr = ref_element_addr [immutable] %e : $Buffer, #Buffer.i
+  debug_value %e : $Buffer, var, name "x"
   %i = load %addr : $*Int
   (%u, %b) = begin_cow_mutation %e : $Buffer
   %t = tuple (%i : $Int, %u : $Builtin.Int1, %b : $Buffer)