PNaCl: Add "-pnacl-abi-simplify-{pre,post}opt" meta-passes to "opt"

These meta-passes will be used to replace the pass lists that are
currently in the pnacl-ld.py driver script in the NaCl repo.

I've moved the comments across from pnacl-ld.py and added a couple
more comments for ExpandByVal and StripMetadata.

Fix the declaration of createResolveAliasesPass().

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3435
TEST=new *.ll tests + tested with change to pnacl-ld.py

Review URL: https://codereview.chromium.org/15669002

7 files changed, 160 insertions, 1 deletions

diff --git a/include/llvm/Transforms/NaCl.h b/include/llvm/Transforms/NaCl.h
index af1dee2ebe..3b9ce35dc8 100644
--- a/include/llvm/Transforms/NaCl.h
+++ b/include/llvm/Transforms/NaCl.h
@@ -16,6 +16,7 @@ class BasicBlockPass;
 class FunctionPass;
 class Instruction;
 class ModulePass;
+class PassManager;
 class Use;
 class Value;
 
@@ -36,6 +37,9 @@ ModulePass *createRewritePNaClLibraryCallsPass();
 ModulePass *createStripMetadataPass();
 FunctionPass *createInsertDivideCheckPass();
 
+void PNaClABISimplifyAddPreOptPasses(PassManager &PM);
+void PNaClABISimplifyAddPostOptPasses(PassManager &PM);
+
 Instruction *PhiSafeInsertPt(Use *U);
 void PhiSafeReplaceUses(Use *U, Value *NewVal);
 
diff --git a/lib/Transforms/NaCl/CMakeLists.txt b/lib/Transforms/NaCl/CMakeLists.txt
index 1fabdbc1db..a98d929f83 100644
--- a/lib/Transforms/NaCl/CMakeLists.txt
+++ b/lib/Transforms/NaCl/CMakeLists.txt
@@ -11,6 +11,7 @@ add_llvm_library(LLVMNaClTransforms
   InsertDivideCheck.cpp
   FlattenGlobals.cpp
   GlobalCleanup.cpp
+  PNaClABISimplify.cpp
   PromoteIntegers.cpp
   ReplacePtrsWithInts.cpp
   RewritePNaClLibraryCalls.cpp
diff --git a/lib/Transforms/NaCl/GlobalCleanup.cpp b/lib/Transforms/NaCl/GlobalCleanup.cpp
index 00e15b39a5..55886f8f7d 100644
--- a/lib/Transforms/NaCl/GlobalCleanup.cpp
+++ b/lib/Transforms/NaCl/GlobalCleanup.cpp
@@ -113,6 +113,6 @@ bool ResolveAliases::runOnModule(Module &M) {
   return Modified;
 }
 
-ModulePass *createResolveAliasesPass() {
+ModulePass *llvm::createResolveAliasesPass() {
   return new ResolveAliases();
 }
diff --git a/lib/Transforms/NaCl/PNaClABISimplify.cpp b/lib/Transforms/NaCl/PNaClABISimplify.cpp
new file mode 100644
index 0000000000..9d7713139a
--- /dev/null
+++ b/lib/Transforms/NaCl/PNaClABISimplify.cpp
@@ -0,0 +1,65 @@
+//===-- PNaClABISimplify.cpp - Lists PNaCl ABI simplification passes ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the meta-passes "-pnacl-abi-simplify-preopt"
+// and "-pnacl-abi-simplify-postopt".  It lists their constituent
+// passes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/NaCl.h"
+#include "llvm/PassManager.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/NaCl.h"
+#include "llvm/Transforms/Scalar.h"
+
+using namespace llvm;
+
+void llvm::PNaClABISimplifyAddPreOptPasses(PassManager &PM) {
+  // LowerInvoke prevents use of C++ exception handling, which is not
+  // yet supported in the PNaCl ABI.
+  PM.add(createLowerInvokePass());
+  // Remove landingpad blocks made unreachable by LowerInvoke.
+  PM.add(createCFGSimplificationPass());
+
+  PM.add(createExpandVarArgsPass());
+  PM.add(createExpandCtorsPass());
+  PM.add(createResolveAliasesPass());
+  PM.add(createExpandTlsPass());
+  // GlobalCleanup needs to run after ExpandTls because
+  // __tls_template_start etc. are extern_weak before expansion
+  PM.add(createGlobalCleanupPass());
+  // Strip dead prototytes to appease the intrinsic ABI checks
+  // (ExpandVarArgs leaves around var-arg intrinsics).
+  PM.add(createStripDeadPrototypesPass());
+}
+
+void llvm::PNaClABISimplifyAddPostOptPasses(PassManager &PM) {
+  // We place ExpandByVal after optimization passes because some byval
+  // arguments can be expanded away by the ArgPromotion pass.  Leaving
+  // in "byval" during optimization also allows some dead stores to be
+  // eliminated, because "byval" is a stronger constraint than what
+  // ExpandByVal expands it to.
+  PM.add(createExpandByValPass());
+
+  // We place StripMetadata after optimization passes because
+  // optimizations depend on the metadata.
+  PM.add(createStripMetadataPass());
+
+  // FlattenGlobals introduces ConstantExpr bitcasts of globals which
+  // are expanded out later.
+  PM.add(createFlattenGlobalsPass());
+
+  // We should not place arbitrary passes after ExpandConstantExpr
+  // because they might reintroduce ConstantExprs.  However,
+  // ExpandGetElementPtr must follow ExpandConstantExpr to expand the
+  // getelementptr instructions it creates.
+  PM.add(createExpandConstantExprPass());
+  PM.add(createExpandGetElementPtrPass());
+}
diff --git a/test/Transforms/NaCl/pnacl-abi-simplify-postopt.ll b/test/Transforms/NaCl/pnacl-abi-simplify-postopt.ll
new file mode 100644
index 0000000000..a1ea6dc0ca
--- /dev/null
+++ b/test/Transforms/NaCl/pnacl-abi-simplify-postopt.ll
@@ -0,0 +1,16 @@
+; RUN: opt %s -pnacl-abi-simplify-postopt -S | FileCheck %s
+
+; "-pnacl-abi-simplify-postopt" runs various passes which are tested
+; thoroughly in other *.ll files.  This file is a smoke test to check
+; that the passes work together OK.
+
+
+@var = global i32 256
+; CHECK: @var = global [4 x i8]
+
+define i16 @read_var() {
+  %val = load i16* bitcast (i32* @var to i16*)
+  ret i16 %val
+}
+; CHECK: = bitcast [4 x i8]* @var
+; CHECK-NEXT: load i16*
diff --git a/test/Transforms/NaCl/pnacl-abi-simplify-preopt.ll b/test/Transforms/NaCl/pnacl-abi-simplify-preopt.ll
new file mode 100644
index 0000000000..1cf7377559
--- /dev/null
+++ b/test/Transforms/NaCl/pnacl-abi-simplify-preopt.ll
@@ -0,0 +1,38 @@
+; RUN: opt %s -pnacl-abi-simplify-preopt -S | FileCheck %s
+
+; "-pnacl-abi-simplify-preopt" runs various passes which are tested
+; thoroughly in other *.ll files.  This file is a smoke test to check
+; that "-pnacl-abi-simplify-preopt" runs what it's supposed to run.
+
+declare void @ext_func()
+
+
+define void @invoke_func() {
+  invoke void @ext_func() to label %cont unwind label %lpad
+cont:
+  ret void
+lpad:
+  %lp = landingpad { i8*, i32 } personality i8* null cleanup
+  ret void
+}
+; CHECK-NOT: invoke void @ext_func()
+; CHECK-NOT: landingpad
+
+
+define void @varargs_func(...) {
+  ret void
+}
+; CHECK-NOT: @varargs_func(...)
+
+
+@llvm.global_ctors = appending global [0 x { i32, void ()* }] zeroinitializer
+; CHECK-NOT: @llvm.global_ctors
+
+@tls_var = thread_local global i32 0
+; CHECK-NOT: thread_local
+
+@alias = alias i32* @tls_var
+; CHECK-NOT: @alias
+
+@weak_ref = extern_weak global i8*
+; CHECK-NOT: extern_weak
diff --git a/tools/opt/opt.cpp b/tools/opt/opt.cpp
index 3179e17733..35e18d02ad 100644
--- a/tools/opt/opt.cpp
+++ b/tools/opt/opt.cpp
@@ -45,6 +45,7 @@
 #include "llvm/Target/TargetLibraryInfo.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
+#include "llvm/Transforms/NaCl.h"  // @LOCALMOD
 #include <algorithm>
 #include <memory>
 using namespace llvm;
@@ -127,6 +128,18 @@ static cl::opt<bool>
 OptLevelO3("O3",
            cl::desc("Optimization level 3. Similar to clang -O3"));
 
+// @LOCALMOD-BEGIN
+static cl::opt<bool>
+PNaClABISimplifyPreOpt(
+    "pnacl-abi-simplify-preopt",
+    cl::desc("PNaCl ABI simplifications for before optimizations"));
+
+static cl::opt<bool>
+PNaClABISimplifyPostOpt(
+    "pnacl-abi-simplify-postopt",
+    cl::desc("PNaCl ABI simplifications for after optimizations"));
+// @LOCALMOD-END
+
 static cl::opt<std::string>
 TargetTriple("mtriple", cl::desc("Override target triple for module"));
 
@@ -760,6 +773,20 @@ int main(int argc, char **argv) {
       OptLevelO3 = false;
     }
 
+    // @LOCALMOD-BEGIN
+    if (PNaClABISimplifyPreOpt &&
+        PNaClABISimplifyPreOpt.getPosition() < PassList.getPosition(i)) {
+      PNaClABISimplifyAddPreOptPasses(Passes);
+      PNaClABISimplifyPreOpt = false;
+    }
+
+    if (PNaClABISimplifyPostOpt &&
+        PNaClABISimplifyPostOpt.getPosition() < PassList.getPosition(i)) {
+      PNaClABISimplifyAddPostOptPasses(Passes);
+      PNaClABISimplifyPostOpt = false;
+    }
+    // @LOCALMOD-END
+
     const PassInfo *PassInf = PassList[i];
     Pass *P = 0;
     if (PassInf->getNormalCtor())
@@ -832,6 +859,14 @@ int main(int argc, char **argv) {
     FPasses->doFinalization();
   }
 
+  // @LOCALMOD-BEGIN
+  if (PNaClABISimplifyPreOpt)
+    PNaClABISimplifyAddPreOptPasses(Passes);
+
+  if (PNaClABISimplifyPostOpt)
+    PNaClABISimplifyAddPostOptPasses(Passes);
+  // @LOCALMOD-END
+
   // Check that the module is well formed on completion of optimization
   if (!NoVerify && !VerifyEach)
     Passes.add(createVerifierPass());