4749 - speed up tests

When we implemented 'read' our apps went over 0x1000 bytes, so I grew the
initial segment size. But that slowed down emulation because each test
was reallocating all segments. Now we allocate small segments at the start,
and grow them gradually as needed.

1 files changed, 14 insertions, 8 deletions

diff --git a/subx/010---vm.cc b/subx/010---vm.cc
index a71d431f..24051ec4 100644
--- a/subx/010---vm.cc
+++ b/subx/010---vm.cc
@@ -122,12 +122,8 @@ struct vma {
   uint32_t start;  // inclusive
   uint32_t end;  // exclusive
   vector<uint8_t> _data;
-  vma(uint32_t s, uint32_t e) :start(s), end(e) {
-    _data.resize(end-start);
-  }
-  vma(uint32_t s) :start(s), end(s+INITIAL_SEGMENT_SIZE) {
-    _data.resize(end-start);
-  }
+  vma(uint32_t s, uint32_t e) :start(s), end(e) {}
+  vma(uint32_t s) :start(s), end(s+INITIAL_SEGMENT_SIZE) {}
   bool match(uint32_t a) {
     return a >= start && a < end;
   }
@@ -136,7 +132,18 @@ struct vma {
   }
   uint8_t& data(uint32_t a) {
     assert(match(a));
-    return _data.at(a-start);
+    uint32_t result_index = a-start;
+    if (_data.size() <= result_index) {
+      const int align = 0x1000;
+      uint32_t result_size = result_index + 1;  // size needed for result_index to be valid
+      #define align_upwards(x, align)  (((x)+(align)-1) & -(align))
+      uint32_t new_size = align_upwards(result_size, align);
+      #undef align_upwards
+      if (new_size > end-start)
+        new_size = end-start;
+      _data.resize(new_size);
+    }
+    return _data.at(result_index);
   }
   void grow_until(uint32_t new_end_address) {
     if (new_end_address < end) return;
@@ -144,7 +151,6 @@ struct vma {
     void sanity_check(uint32_t start, uint32_t end);
     sanity_check(start, new_end_address);
     end = new_end_address;
-    _data.resize(new_end_address - start);
   }
   // End vma Methods
 };