Add some __builtin_expect magic to StringMap.

Tombstones and full hash collisions are rare, mark the "empty"
and "no collision" paths as likely. The bug in simplifycfg
that prevented the hints from being picked during selfhost
up was fixed recently :)

llvm-svn: 162874

1 files changed, 5 insertions, 4 deletions

diff --git a/llvm/lib/Support/StringMap.cpp b/llvm/lib/Support/StringMap.cpp
index c2fc261df3a..9ac1f867fdd 100644
--- a/llvm/lib/Support/StringMap.cpp
+++ b/llvm/lib/Support/StringMap.cpp
@@ -13,6 +13,7 @@
 
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/Compiler.h"
 #include <cassert>
 using namespace llvm;
 
@@ -69,7 +70,7 @@ unsigned StringMapImpl::LookupBucketFor(StringRef Name) {
   while (1) {
     StringMapEntryBase *BucketItem = TheTable[BucketNo];
     // If we found an empty bucket, this key isn't in the table yet, return it.
-    if (BucketItem == 0) {
+    if (LLVM_LIKELY(BucketItem == 0)) {
       // If we found a tombstone, we want to reuse the tombstone instead of an
       // empty bucket.  This reduces probing.
       if (FirstTombstone != -1) {
@@ -84,7 +85,7 @@ unsigned StringMapImpl::LookupBucketFor(StringRef Name) {
     if (BucketItem == getTombstoneVal()) {
       // Skip over tombstones.  However, remember the first one we see.
       if (FirstTombstone == -1) FirstTombstone = BucketNo;
-    } else if (HashTable[BucketNo] == FullHashValue) {
+    } else if (LLVM_LIKELY(HashTable[BucketNo] == FullHashValue)) {
       // If the full hash value matches, check deeply for a match.  The common
       // case here is that we are only looking at the buckets (for item info
       // being non-null and for the full hash value) not at the items.  This
@@ -123,12 +124,12 @@ int StringMapImpl::FindKey(StringRef Key) const {
   while (1) {
     StringMapEntryBase *BucketItem = TheTable[BucketNo];
     // If we found an empty bucket, this key isn't in the table yet, return.
-    if (BucketItem == 0)
+    if (LLVM_LIKELY(BucketItem == 0))
       return -1;
     
     if (BucketItem == getTombstoneVal()) {
       // Ignore tombstones.
-    } else if (HashTable[BucketNo] == FullHashValue) {
+    } else if (LLVM_LIKELY(HashTable[BucketNo] == FullHashValue)) {
       // If the full hash value matches, check deeply for a match.  The common
       // case here is that we are only looking at the buckets (for item info
       // being non-null and for the full hash value) not at the items.  This