Memory64Lowering: Ignore data segments with non-const iniital offset (#5074)

This is the case for dynamic linking where the segment offset are
derived from he `__memory_base` import.

1 files changed, 31 insertions, 3 deletions

diff --git a/src/passes/Memory64Lowering.cpp b/src/passes/Memory64Lowering.cpp
index 15f3a7719..661d6cdae 100644
--- a/src/passes/Memory64Lowering.cpp
+++ b/src/passes/Memory64Lowering.cpp
@@ -21,12 +21,16 @@
 // TODO(wvo): make this run in parallel if needed.
 
 #include "ir/bits.h"
+#include "ir/import-utils.h"
 #include "pass.h"
 #include "wasm-builder.h"
 #include "wasm.h"
 
 namespace wasm {
 
+static Name MEMORY_BASE("__memory_base");
+static Name MEMORY_BASE32("__memory_base32");
+
 struct Memory64Lowering : public WalkerPass<PostWalker<Memory64Lowering>> {
 
   void wrapAddress64(Expression*& ptr, Name memoryName) {
@@ -126,9 +130,33 @@ struct Memory64Lowering : public WalkerPass<PostWalker<Memory64Lowering>> {
 
   void visitDataSegment(DataSegment* segment) {
     if (!segment->isPassive) {
-      auto* c = segment->offset->cast<Const>();
-      c->value = Literal(static_cast<uint32_t>(c->value.geti64()));
-      c->type = Type::i32;
+      if (auto* c = segment->offset->dynCast<Const>()) {
+        c->value = Literal(static_cast<uint32_t>(c->value.geti64()));
+        c->type = Type::i32;
+      } else if (auto* get = segment->offset->dynCast<GlobalGet>()) {
+        auto& module = *getModule();
+        auto* g = module.getGlobal(get->name);
+        if (g->imported() && g->base == MEMORY_BASE) {
+          ImportInfo info(module);
+          auto* memoryBase32 = info.getImportedGlobal(g->module, MEMORY_BASE32);
+          if (!memoryBase32) {
+            Builder builder(module);
+            memoryBase32 = builder
+                             .makeGlobal(MEMORY_BASE32,
+                                         Type::i32,
+                                         builder.makeConst(int32_t(0)),
+                                         Builder::Immutable)
+                             .release();
+            memoryBase32->module = g->module;
+            memoryBase32->base = MEMORY_BASE32;
+            module.addGlobal(memoryBase32);
+          }
+          // Use this alternative import when initializing the segment.
+          assert(memoryBase32);
+          get->type = Type::i32;
+          get->name = memoryBase32->name;
+        }
+      }
     }
   }
 };