If all else is equal the compiler will assume the if branch is more likely than the else branch.

This is based on experience since gcc 2.8 and til today, and is not a definitive truth. Just more likely.
if (criteria) {
    most_likely_executed code
} else {
    less_likely_executed code
}

While a single branched if is assumed less likely.

1 files changed, 10 insertions, 10 deletions

diff --git a/vespalib/src/vespa/vespalib/util/alloc.cpp b/vespalib/src/vespa/vespalib/util/alloc.cpp
index 0a83d39ca09..ed620ec0afe 100644
--- a/vespalib/src/vespa/vespalib/util/alloc.cpp
+++ b/vespalib/src/vespa/vespalib/util/alloc.cpp
@@ -454,33 +454,33 @@ AutoAllocator::resize_inplace(PtrAndSize current, size_t newSize) const {
 
 MMapAllocator::PtrAndSize
 AutoAllocator::alloc(size_t sz) const {
-    if (useMMap(sz)) {
-        sz = roundUpToHugePages(sz);
-        return MMapAllocator::salloc(sz, nullptr);
-    } else {
+    if ( ! useMMap(sz)) {
         if (_alignment == 0) {
             return HeapAllocator::salloc(sz);
         } else {
             return AlignedHeapAllocator(_alignment).alloc(sz);
         }
+    } else {
+        sz = roundUpToHugePages(sz);
+        return MMapAllocator::salloc(sz, nullptr);
     }
 }
 
 void
 AutoAllocator::free(PtrAndSize alloc) const {
-    if (isMMapped(alloc.second)) {
-        return MMapAllocator::sfree(alloc);
-    } else {
+    if ( ! isMMapped(alloc.second)) {
         return HeapAllocator::sfree(alloc);
+    } else {
+        return MMapAllocator::sfree(alloc);
     }
 }
 
 void
 AutoAllocator::free(void * ptr, size_t sz) const {
-    if (useMMap(sz)) {
-        return MMapAllocator::sfree(PtrAndSize(ptr, roundUpToHugePages(sz)));
-    } else {
+    if ( ! useMMap(sz)) {
         return HeapAllocator::sfree(PtrAndSize(ptr, sz));
+    } else {
+        return MMapAllocator::sfree(PtrAndSize(ptr, roundUpToHugePages(sz)));
     }
 }