[llvm-branch-commits] [llvm] 28e8baf - [𝘀𝗽𝗿] initial version

[Scott Linder via llvm-branch-commits]

Author: Scott Linder
Date: 2023-11-08T21:05:40Z
New Revision: 28e8baf03efd7ba43a2af4afb3831caa511880ca

URL: https://github.com/llvm/llvm-project/commit/28e8baf03efd7ba43a2af4afb3831caa511880ca
DIFF: https://github.com/llvm/llvm-project/commit/28e8baf03efd7ba43a2af4afb3831caa511880ca.diff

LOG: [𝘀𝗽𝗿] initial version

Created using spr 1.3.6-beta.1

Added: 
    

Modified: 
    llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
index 55a0afcf7a33f16..8b67580b9ba50b0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
@@ -373,6 +373,18 @@ static void handleNewDebugValue(InlinedEntity Var, const MachineInstr &DV,
                                 DbgValueHistoryMap &HistMap) {
   EntryIndex NewIndex;
   if (HistMap.startDbgValue(Var, DV, NewIndex)) {
+    // As we already need to iterate all LiveEntries when handling a DbgValue,
+    // we use this map to avoid a more expensive check against RegVars. There
+    // is an assert that we handle this correclty in addRegDescribedVar.
+    //
+    // In other terms, the presense in this map indicates the presense of a
+    // corresponding entry in RegVars.
+    //
+    // The bool value then tracks whether an entry is to be retained (true) or
+    // removed (false); as we end previous entries we speculatively assume they
+    // can be dropped from RegVars, but we then also visit the new entry whose
+    // set of debug register operands may overlap and "save" a reg from being
+    // dropped.
     SmallDenseMap<unsigned, bool, 4> TrackedRegs;
 
     // If we have created a new debug value entry, close all preceding
@@ -466,9 +478,6 @@ void llvm::calculateDbgEntityHistory(const MachineFunction *MF,
     for (const auto &MI : MBB) {
       if (MI.isDebugValue()) {
         assert(MI.getNumOperands() > 1 && "Invalid DBG_VALUE instruction!");
-        // Use the base variable (without any DW_OP_piece expressions)
-        // as index into History. The full variables including the
-        // piece expressions are attached to the MI.
         const DILocalVariable *RawVar = MI.getDebugVariable();
         assert(RawVar->isValidLocationForIntrinsic(MI.getDebugLoc()) &&
                "Expected inlined-at fields to agree");
@@ -492,8 +501,7 @@ void llvm::calculateDbgEntityHistory(const MachineFunction *MF,
       if (MI.isMetaInstruction())
         continue;
 
-      // Not a DBG_VALUE instruction. It may clobber registers which describe
-      // some variables.
+      // Other instruction may clobber registers which describe some variables.
       for (const MachineOperand &MO : MI.operands()) {
         if (MO.isReg() && MO.isDef() && MO.getReg()) {
           // Ignore call instructions that claim to clobber SP. The AArch64