[PATCH] D79961: [PGO] Fix computation of fuction Hash

[serge via Phabricator via cfe-commits]

serge-sans-paille updated this revision to Diff 264552.
serge-sans-paille edited the summary of this revision.
serge-sans-paille added a comment.

Updated summary + removed namespace.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D79961/new/

https://reviews.llvm.org/D79961

Files:
  clang/lib/CodeGen/CodeGenPGO.cpp
  clang/test/Profile/c-collision.c


Index: clang/test/Profile/c-collision.c
===================================================================
--- /dev/null
+++ clang/test/Profile/c-collision.c
@@ -0,0 +1,22 @@
+// Test that a slight change in the code leads to a different hash.
+// RUN: %clang_cc1 -UEXTRA -triple x86_64-unknown-linux-gnu -main-file-name c-collision.c %s -o - -emit-llvm -fprofile-instrument=clang | FileCheck %s --check-prefix=CHECK-NOEXTRA
+// RUN: %clang_cc1 -DEXTRA -triple x86_64-unknown-linux-gnu -main-file-name c-collision.c %s -o - -emit-llvm -fprofile-instrument=clang | FileCheck %s --check-prefix=CHECK-EXTRA
+
+// CHECK-NOEXTRA: @__profd_foo = private global { {{.*}} } { i64 6699318081062747564, i64 7156072912471487002,
+// CHECK-EXTRA:   @__profd_foo = private global { {{.*}} } { i64 6699318081062747564, i64 -4383447408116050035,
+
+extern int bar;
+void foo() {
+  if (bar) {
+  }
+  if (bar) {
+  }
+  if (bar) {
+    if (bar) {
+#ifdef EXTRA
+      if (bar) {
+      }
+#endif
+    }
+  }
+}
Index: clang/lib/CodeGen/CodeGenPGO.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenPGO.cpp
+++ clang/lib/CodeGen/CodeGenPGO.cpp
@@ -747,13 +747,15 @@
     return Working;
 
   // Check for remaining work in Working.
-  if (Working)
-    MD5.update(Working);
+  if (Working) {
+    using namespace llvm::support;
+    uint64_t Swapped = endian::byte_swap<uint64_t, little>(Working);
+    MD5.update(llvm::makeArrayRef((uint8_t *)&Swapped, sizeof(Swapped)));
+  }
 
   // Finalize the MD5 and return the hash.
   llvm::MD5::MD5Result Result;
   MD5.final(Result);
-  using namespace llvm::support;
   return Result.low();
 }
 


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