[lldb] [llvm] [mlir] [DebugInfo] Add symbolic branches to DIExpression (PR #210850)

[Eric Christopher via llvm-commits]

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@@ -69,11 +89,41 @@ void DIEDwarfExpression::enableTemporaryBuffer() {
 void DIEDwarfExpression::disableTemporaryBuffer() { IsBuffering = false; }
 
 unsigned DIEDwarfExpression::getTemporaryBufferSize() {
-  return TmpDIE.computeSize(AP.getDwarfFormParams());
+  unsigned Size = 0;
+  for (const DIEValue &V : TmpDIE.values())
+    Size += V.sizeOf(AP.getDwarfFormParams());
+  return Size;
 }
 
 void DIEDwarfExpression::commitTemporaryBuffer() { OutDIE.takeValues(TmpDIE); }
 
+void DIEDwarfExpression::replaceTemporaryBufferData(unsigned PlaceholderOffset,
+                                                    uint64_t Replacement,
+                                                    unsigned PlaceholderSize) {
+  // Walk the encoded values until the cursor reaches the placeholder.
+  unsigned ByteCursor = 0;
+  for (DIEValue &V : TmpDIE.values()) {
+    unsigned ValueSize = V.sizeOf(AP.getDwarfFormParams());
+    unsigned ValueEnd = ByteCursor + ValueSize;
+    if (ValueEnd <= PlaceholderOffset) {
+      ByteCursor = ValueEnd;
+      continue;
+    }
+
+    // Replace the whole zero placeholder and keep its form, since changing its
+    // encoded size would move every later fixup.
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echristo wrote:

sorry, I'd apparently missed this. Sadly the two bytes are required so there's not much more densification we could do here. 

https://github.com/llvm/llvm-project/pull/210850