[DebugInfo] Support DIArgList in DbgVariableIntrinsic

This patch updates DbgVariableIntrinsics to support use of a DIArgList for the
location operand, resulting in a significant change to its interface. This patch
does not update all IR passes to support multiple location operands in a
dbg.value; the only change is to update the DbgVariableIntrinsic interface and
its uses. All code outside of the intrinsic classes assumes that an intrinsic
will always have exactly one location operand; they will still support
DIArgLists, but only if they contain exactly one Value.

Among other changes, the setOperand and setArgOperand functions in
DbgVariableIntrinsic have been made private. This is to prevent code from
setting the operands of these intrinsics directly, which could easily result in
incorrect/invalid operands being set. This does not prevent these functions from
being called on a debug intrinsic at all, as they can still be called on any
CallInst pointer; it is assumed that any code directly setting the operands on a
generic call instruction is doing so safely. The intention for making these
functions private is to prevent DIArgLists from being overwritten by code that's
naively trying to replace one of the Values it points to, and also to fail fast
if a DbgVariableIntrinsic is updated to use a DIArgList without a valid
corresponding DIExpression.

1 files changed, 4 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index f4bf55d..6e806b0 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -2883,11 +2883,8 @@ class TypePromotionTransaction {
       // including the debug uses. Since we are undoing the replacements,
       // the original debug uses must also be reinstated to maintain the
       // correctness and utility of debug value instructions.
-      for (auto *DVI: DbgValues) {
-        LLVMContext &Ctx = Inst->getType()->getContext();
-        auto *MV = MetadataAsValue::get(Ctx, ValueAsMetadata::get(Inst));
-        DVI->setOperand(0, MV);
-      }
+      for (auto *DVI : DbgValues)
+        DVI->replaceVariableLocationOp(DVI->getVariableLocationOp(0), Inst);
     }
   };
 
@@ -7878,7 +7875,7 @@ bool CodeGenPrepare::fixupDbgValue(Instruction *I) {
   DbgValueInst &DVI = *cast<DbgValueInst>(I);
 
   // Does this dbg.value refer to a sunk address calculation?
-  Value *Location = DVI.getVariableLocation();
+  Value *Location = DVI.getVariableLocationOp(0);
   WeakTrackingVH SunkAddrVH = SunkAddrs[Location];
   Value *SunkAddr = SunkAddrVH.pointsToAliveValue() ? SunkAddrVH : nullptr;
   if (SunkAddr) {
@@ -7886,8 +7883,7 @@ bool CodeGenPrepare::fixupDbgValue(Instruction *I) {
     // opportunity to be accurately lowered. This update may change the type of
     // pointer being referred to; however this makes no difference to debugging
     // information, and we can't generate bitcasts that may affect codegen.
-    DVI.setOperand(0, MetadataAsValue::get(DVI.getContext(),
-                                           ValueAsMetadata::get(SunkAddr)));
+    DVI.replaceVariableLocationOp(Location, SunkAddr);
     return true;
   }
   return false;