Properly align the stack pointer

* Properly align the stack pointer

By default (if no global base is given) the global base is 1, which
seems wrong. In this case the stack pointer gets an address of 1, which
is unaligned and definitely wrong. So, start the global base at 0 instead of
1 by default and align the stack pointer. Also factor allocation of
statics into a function.

* unconditionally allocate stack pointer; explicitly reserve address 0

1 files changed, 13 insertions, 0 deletions

diff --git a/src/support/utilities.h b/src/support/utilities.h
index 77263a78e..d35b2b34a 100644
--- a/src/support/utilities.h
+++ b/src/support/utilities.h
@@ -35,6 +35,19 @@ inline Destination bit_cast(const Source& source) {
   return destination;
 }
 
+inline bool isPowerOf2(uint32_t v) {
+  return v && !(v & (v - 1));
+}
+
+inline size_t alignAddr(size_t address, size_t alignment) {
+  assert(alignment && isPowerOf2((uint32_t)alignment) &&
+         "Alignment is not a power of two!");
+
+  assert(address + alignment - 1 >= address);
+
+  return ((address + alignment - 1) & ~(alignment - 1));
+}
+
 }  // namespace wasm
 
 #endif   // wasm_support_utilities_h