[PATCH] D44223: [ms] Emit vtordisp initializers in a deterministic order.

[Nico Weber via Phabricator via cfe-commits]

thakis created this revision.
thakis added a reviewer: rnk.

No effective behavior change, just for cleanliness.

Fixes PR36159.


https://reviews.llvm.org/D44223

Files:
  lib/CodeGen/MicrosoftCXXABI.cpp


Index: lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- lib/CodeGen/MicrosoftCXXABI.cpp
+++ lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1196,15 +1196,22 @@
   unsigned AS = getThisAddress(CGF).getAddressSpace();
   llvm::Value *Int8This = nullptr;  // Initialize lazily.
 
-  for (VBOffsets::const_iterator I = VBaseMap.begin(), E = VBaseMap.end();
-        I != E; ++I) {
-    if (!I->second.hasVtorDisp())
+  // Emit vtordisps in vbase offset order, to have deterministic output.
+  typedef VBOffsets::value_type VBaseEntry;
+  SmallVector<VBaseEntry, 4> VBases(VBaseMap.begin(), VBaseMap.end());
+  std::stable_sort(VBases.begin(), VBases.end(),
+                   [](const VBaseEntry &a, const VBaseEntry &b) {
+                     return a.second.VBaseOffset < b.second.VBaseOffset;
+                   });
+
+  for (const VBaseEntry E : VBases) {
+    if (!E.second.hasVtorDisp())
       continue;
 
     llvm::Value *VBaseOffset =
-        GetVirtualBaseClassOffset(CGF, getThisAddress(CGF), RD, I->first);
+        GetVirtualBaseClassOffset(CGF, getThisAddress(CGF), RD, E.first);
     uint64_t ConstantVBaseOffset =
-        Layout.getVBaseClassOffset(I->first).getQuantity();
+        Layout.getVBaseClassOffset(E.first).getQuantity();
 
     // vtorDisp_for_vbase = vbptr[vbase_idx] - offsetof(RD, vbase).
     llvm::Value *VtorDispValue = Builder.CreateSub(


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