[DebugInfo] Replace debug uses in replaceUsesOutsideBlock

Value::replaceUsesOutsideBlock doesn't replace debug uses which leads to an
unnecessary reduction in variable location coverage. Fix this, add a unittest for
it, and add a regression test demonstrating the change through instcombine's
replacedSelectWithOperand.

Reviewed By: djtodoro

Differential Revision: https://reviews.llvm.org/D99169

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 7003508..e0b72dc 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -18,6 +18,7 @@
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/DerivedUser.h"
 #include "llvm/IR/GetElementPtrTypeIterator.h"
@@ -531,6 +532,17 @@ void Value::replaceNonMetadataUsesWith(Value *New) {
   doRAUW(New, ReplaceMetadataUses::No);
 }
 
+/// Replace llvm.dbg.* uses of MetadataAsValue(ValueAsMetadata(V)) outside BB
+/// with New.
+static void replaceDbgUsesOutsideBlock(Value *V, Value *New, BasicBlock *BB) {
+  SmallVector<DbgVariableIntrinsic *> DbgUsers;
+  findDbgUsers(DbgUsers, V);
+  for (auto *DVI : DbgUsers) {
+    if (DVI->getParent() != BB)
+      DVI->replaceVariableLocationOp(V, New);
+  }
+}
+
 // Like replaceAllUsesWith except it does not handle constants or basic blocks.
 // This routine leaves uses within BB.
 void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
@@ -541,6 +553,7 @@ void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
          "replaceUses of value with new value of different type!");
   assert(BB && "Basic block that may contain a use of 'New' must be defined\n");
 
+  replaceDbgUsesOutsideBlock(this, New, BB);
   replaceUsesWithIf(New, [BB](Use &U) {
     auto *I = dyn_cast<Instruction>(U.getUser());
     // Don't replace if it's an instruction in the BB basic block.