[DSE] Use precise loc for memcpy_chk during overwrite checks.

Extends the logic from D115167 to memcpy_chk.

Depends on D115167

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D139096

Author: fhahn

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -838,7 +838,8 @@ struct DSEState {
                                       LocationSize Size) const {
     if (auto *CB = dyn_cast<CallBase>(I)) {
       LibFunc F;
-      if (TLI.getLibFunc(*CB, F) && TLI.has(F) && F == LibFunc_memset_chk) {
+      if (TLI.getLibFunc(*CB, F) && TLI.has(F) &&
+          (F == LibFunc_memset_chk || F == LibFunc_memcpy_chk)) {
         // Use the precise location size specified by the 3rd argument
         // for determining KillingI overwrites DeadLoc if it is a memset_chk
         // instruction. memset_chk will write either the amount specified as 3rd

llvm/test/Transforms/DeadStoreElimination/libcalls-chk.ll

@@ -107,8 +107,7 @@ define void @dse_strncpy_chk_test3(ptr noalias %out1, ptr noalias %out2, ptr noa
 
 define void @dse_strncpy_memcpy_chk_test1(ptr noalias %out, ptr noalias %in, i64 %n) {
 ; CHECK-LABEL: @dse_strncpy_memcpy_chk_test1(
-; CHECK-NEXT:    store i32 0, ptr [[OUT:%.*]], align 4
-; CHECK-NEXT:    [[CALL_1:%.*]] = tail call ptr @__memcpy_chk(ptr [[OUT]], ptr [[IN:%.*]], i64 100, i64 [[N:%.*]])
+; CHECK-NEXT:    [[CALL_1:%.*]] = tail call ptr @__memcpy_chk(ptr [[OUT:%.*]], ptr [[IN:%.*]], i64 100, i64 [[N:%.*]])
 ; CHECK-NEXT:    ret void
 ;
   store i32 0, ptr %out