LTO: Hash the set of imported symbols for each module.

This set may affect code generation and is sensitive to link order (and
possibly in the future to the linker's choice of prevailing symbol), so we
need to include it.

Differential Revision: https://reviews.llvm.org/D30586

llvm-svn: 296907

lib/LTO/LTO.cpp

@@ -84,6 +84,18 @@ static void computeCacheKey(
     Data[3] = I >> 24;
     Hasher.update(ArrayRef<uint8_t>{Data, 4});
   };
+  auto AddUint64 = [&](uint64_t I) {
+    uint8_t Data[8];
+    Data[0] = I;
+    Data[1] = I >> 8;
+    Data[2] = I >> 16;
+    Data[3] = I >> 24;
+    Data[4] = I >> 32;
+    Data[5] = I >> 40;
+    Data[6] = I >> 48;
+    Data[7] = I >> 56;
+    Hasher.update(ArrayRef<uint8_t>{Data, 8});
+  };
   AddString(Conf.CPU);
   // FIXME: Hash more of Options. For now all clients initialize Options from
   // command-line flags (which is unsupported in production), but may set
@@ -112,10 +124,16 @@ static void computeCacheKey(
     // The export list can impact the internalization, be conservative here
     Hasher.update(ArrayRef<uint8_t>((uint8_t *)&F, sizeof(F)));
 
-  // Include the hash for every module we import functions from
+  // Include the hash for every module we import functions from. The set of
+  // imported symbols for each module may affect code generation and is
+  // sensitive to link order, so include that as well.
   for (auto &Entry : ImportList) {
     auto ModHash = Index.getModuleHash(Entry.first());
     Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
+
+    AddUint64(Entry.second.size());
+    for (auto &Fn : Entry.second)
+      AddUint64(Fn.first);
   }
 
   // Include the hash for the resolved ODR.

test/ThinLTO/X86/Inputs/cache-import-lists1.ll

@@ -0,0 +1,11 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @f1() {
+  call void @linkonce_odr()
+  ret void
+}
+
+define linkonce_odr void @linkonce_odr() {
+  ret void
+}

test/ThinLTO/X86/Inputs/cache-import-lists2.ll

@@ -0,0 +1,11 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @f2() {
+  call void @linkonce_odr()
+  ret void
+}
+
+define linkonce_odr void @linkonce_odr() {
+  ret void
+}

test/ThinLTO/X86/cache-import-lists.ll

@@ -0,0 +1,24 @@
+; RUN: opt -module-hash -module-summary %s -o %t.bc
+; RUN: opt -module-hash -module-summary %S/Inputs/cache-import-lists1.ll -o %t1.bc
+; RUN: opt -module-hash -module-summary %S/Inputs/cache-import-lists2.ll -o %t2.bc
+
+; Tests that the hash for t is sensitive to the set of imported functions
+; for each module, which in this case depends on the link order (the function
+; linkonce_odr will be imported from either t1 or t2, whichever comes first).
+
+; RUN: rm -rf %t.cache
+; RUN: llvm-lto2 -cache-dir %t.cache -o %t.o %t.bc %t1.bc %t2.bc -r=%t.bc,main,plx -r=%t.bc,f1,lx -r=%t.bc,f2,lx -r=%t1.bc,f1,plx -r=%t1.bc,linkonce_odr,plx -r=%t2.bc,f2,plx -r=%t2.bc,linkonce_odr,lx
+; RUN: llvm-lto2 -cache-dir %t.cache -o %t.o %t.bc %t2.bc %t1.bc -r=%t.bc,main,plx -r=%t.bc,f1,lx -r=%t.bc,f2,lx -r=%t2.bc,f2,plx -r=%t2.bc,linkonce_odr,plx -r=%t1.bc,f1,plx -r=%t1.bc,linkonce_odr,lx
+; RUN: ls %t.cache | count 6
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @main() {
+  call void @f1()
+  call void @f2()
+  ret void
+}
+
+declare void @f1()
+declare void @f2()