[IRGen] Run instrprof lowering before all other module passes

This matches clang's behavior. It also makes it possible to, e.g compile
with ASan *and* Code Coverage enabled.

Fixes rdar://problem/26850611.

Author: vedantk

lib/IRGen/IRGen.cpp

@@ -229,6 +229,11 @@ void swift::performLLVMOptimizations(IRGenOptions &Opts, llvm::Module *Module,
   legacy::PassManager ModulePasses;
   ModulePasses.add(createTargetTransformInfoWrapperPass(
       TargetMachine->getTargetIRAnalysis()));
+
+  // If we're generating a profile, add the lowering pass now.
+  if (Opts.GenerateProfile)
+    ModulePasses.add(createInstrProfilingPass());
+
   PMBuilder.populateModulePassManager(ModulePasses);
 
   // The PMBuilder only knows about LLVM AA passes.  We should explicitly add
@@ -242,10 +247,6 @@ void swift::performLLVMOptimizations(IRGenOptions &Opts, llvm::Module *Module,
     }));
   }
 
-  // If we're generating a profile, add the lowering pass now.
-  if (Opts.GenerateProfile)
-    ModulePasses.add(createInstrProfilingPass());
-
   if (Opts.Verify)
     ModulePasses.add(createVerifierPass());
 

test/IRGen/coverage_with_asan.swift

@@ -0,0 +1,4 @@
+// RUN: %target-swift-frontend %s -profile-generate -profile-coverage-mapping -sanitize=address -emit-ir -o - | FileCheck %s
+
+// CHECK: main
+func main() {}