Move DBG_VALUE's that depend on loads to after a

load if the load is moved due to the pre register allocation ld/st optimization pass The issue here is that there can be a scenario where debug information is lost because of the pre register allocation load store optimization pass, where a load who's result describes the debug infomation for a local variable gets moved below the load and that causes the debug information for that load to get lost. Example: Before the Pre Register Allocation Load Store Pass inst_a %2 = ld ... inst_b DBG_VALUE %2, "x", ... %3 = ld ... After the Pass: inst_a inst_b DBG_VALUE %2, "x", ... %2 = ld ... %3 = ld ... The load has now been moved to after the DBG_VAL that uses its result and the debug info for "x" has been lost. What we want is: inst_a inst_b %2 = ld ... DBG_VALUE %2, "x", ... %3 = ld ... Which is what this patch addresses Differential Revision: https://reviews.llvm.org/D145168
llvm · Apr 12, 2023 · 0aaf634 · 0aaf634
1 parent 144562e
commit 0aaf634
Show file tree

Hide file tree

Showing 6 changed files with 918 additions and 10 deletions.
diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -20,6 +20,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator_range.h"
+#include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/Support/Casting.h"
@@ -3770,6 +3771,10 @@ class DebugVariable {
         Fragment(DIExpr ? DIExpr->getFragmentInfo() : std::nullopt),
         InlinedAt(InlinedAt) {}
 
+  DebugVariable(const MachineInstr *MI)
+      : DebugVariable(MI->getDebugVariable(), MI->getDebugExpression(),
+                      MI->getDebugLoc()->getInlinedAt()) {}
+
   const DILocalVariable *getVariable() const { return Variable; }
   std::optional<FragmentInfo> getFragment() const { return Fragment; }
   const DILocation *getInlinedAt() const { return InlinedAt; }