[attrs] Extract the pure inference of function attributes into

a standalone pass.

There is no call graph or even interesting analysis for this part of
function attributes -- it is literally inferring attributes based on the
target library identification. As such, we can do it using a much
simpler module pass that just walks the declarations. This can also
happen much earlier in the pass pipeline which has benefits for any
number of other passes.

In the process, I've cleaned up one particular aspect of the logic which
was necessary in order to separate the two passes cleanly. It now counts
inferred attributes independently rather than just counting all the
inferred attributes as one, and the counts are more clearly explained.

The two test cases we had for this code path are both ... woefully
inadequate and copies of each other. I've kept the superset test and
updated it. We need more testing here, but I had to pick somewhere to
stop fixing everything broken I saw here.

Differential Revision: http://reviews.llvm.org/D15676

llvm-svn: 256466

1 files changed, 14 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 5978b8f59ca..9876efa7b23 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -12,26 +12,26 @@
 //
 //===----------------------------------------------------------------------===//
 
-
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
 #include "llvm-c/Transforms/PassManagerBuilder.h"
 #include "llvm/ADT/SmallVector.h"
-#include "llvm/Analysis/Passes.h"
-#include "llvm/IR/DataLayout.h"
-#include "llvm/IR/FunctionInfo.h"
-#include "llvm/IR/Verifier.h"
-#include "llvm/IR/LegacyPassManager.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/ManagedStatic.h"
 #include "llvm/Analysis/BasicAliasAnalysis.h"
 #include "llvm/Analysis/CFLAliasAnalysis.h"
 #include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/Passes.h"
 #include "llvm/Analysis/ScopedNoAliasAA.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TypeBasedAliasAnalysis.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/FunctionInfo.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Verifier.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ManagedStatic.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/ForceFunctionAttrs.h"
+#include "llvm/Transforms/IPO/InferFunctionAttrs.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Vectorize.h"
 
@@ -220,6 +220,9 @@ void PassManagerBuilder::populateModulePassManager(
   addInitialAliasAnalysisPasses(MPM);
 
   if (!DisableUnitAtATime) {
+    // Infer attributes about declarations if possible.
+    MPM.add(createInferFunctionAttrsLegacyPass());
+
     addExtensionsToPM(EP_ModuleOptimizerEarly, MPM);
 
     MPM.add(createIPSCCPPass());              // IP SCCP
@@ -490,6 +493,9 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
   // Allow forcing function attributes as a debugging and tuning aid.
   PM.add(createForceFunctionAttrsLegacyPass());
 
+  // Infer attributes about declarations if possible.
+  PM.add(createInferFunctionAttrsLegacyPass());
+
   // Propagate constants at call sites into the functions they call.  This
   // opens opportunities for globalopt (and inlining) by substituting function
   // pointers passed as arguments to direct uses of functions.