From 0ecdbe7d6b543256f9225355cc3c315314a2fd57 Mon Sep 17 00:00:00 2001
From: James Molloy <james.molloy@arm.com>
Date: Thu, 19 Nov 2015 08:49:57 +0000
Subject: [PATCH] [FunctionAttrs] Provide a mechanism for adding function
 attributes from the command line

This provides a way to force a function to have certain attributes from the command line. This can be useful when debugging or doing workload exploration, where manually editing IR is tedious or not possible (due to build systems etc).

The syntax is -force-attribute=function_name:attribute_name

All function attributes are parsed except alignstack as it requires an argument.

llvm-svn: 253550
---
 llvm/lib/Transforms/IPO/FunctionAttrs.cpp    | 67 ++++++++++++++++++++
 llvm/test/Transforms/FunctionAttrs/forced.ll | 12 ++++
 2 files changed, 79 insertions(+)
 create mode 100644 llvm/test/Transforms/FunctionAttrs/forced.ll

diff --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index 8a697c3e6afc..e699c5e0df5c 100644
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -23,6 +23,7 @@
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/BasicAliasAnalysis.h"
@@ -52,6 +53,13 @@ STATISTIC(NumNonNullReturn, "Number of function returns marked nonnull");
 STATISTIC(NumAnnotated, "Number of attributes added to library functions");
 STATISTIC(NumNoRecurse, "Number of functions marked as norecurse");
 
+static cl::list<std::string>
+ForceAttributes("force-attribute", cl::Hidden,
+                cl::desc("Add an attribute to a function. This should be a "
+                         "pair of 'function-name:attribute-name', for "
+                         "example -force-add-attribute=foo:noinline. This "
+                         "option can be specified multiple times."));
+
 namespace {
 typedef SmallSetVector<Function *, 8> SCCNodeSet;
 }
@@ -1843,6 +1851,64 @@ static bool addNoRecurseAttrsTopDownOnly(Function *F) {
   return false;
 }
 
+static Attribute::AttrKind parseAttrKind(StringRef Kind) {
+  return StringSwitch<Attribute::AttrKind>(Kind)
+    .Case("alwaysinline", Attribute::AlwaysInline)
+    .Case("builtin", Attribute::Builtin)
+    .Case("cold", Attribute::Cold)
+    .Case("convergent", Attribute::Convergent)
+    .Case("inlinehint", Attribute::InlineHint)
+    .Case("jumptable", Attribute::JumpTable)
+    .Case("minsize", Attribute::MinSize)
+    .Case("naked", Attribute::Naked)
+    .Case("nobuiltin", Attribute::NoBuiltin)
+    .Case("noduplicate", Attribute::NoDuplicate)
+    .Case("noimplicitfloat", Attribute::NoImplicitFloat)
+    .Case("noinline", Attribute::NoInline)
+    .Case("nonlazybind", Attribute::NonLazyBind)
+    .Case("noredzone", Attribute::NoRedZone)
+    .Case("noreturn", Attribute::NoReturn)
+    .Case("norecurse", Attribute::NoRecurse)
+    .Case("nounwind", Attribute::NoUnwind)
+    .Case("optnone", Attribute::OptimizeNone)
+    .Case("optsize", Attribute::OptimizeForSize)
+    .Case("readnone", Attribute::ReadNone)
+    .Case("readonly", Attribute::ReadOnly)
+    .Case("argmemonly", Attribute::ArgMemOnly)
+    .Case("returns_twice", Attribute::ReturnsTwice)
+    .Case("safestack", Attribute::SafeStack)
+    .Case("sanitize_address", Attribute::SanitizeAddress)
+    .Case("sanitize_memory", Attribute::SanitizeMemory)
+    .Case("sanitize_thread", Attribute::SanitizeThread)
+    .Case("ssp", Attribute::StackProtect)
+    .Case("sspreq", Attribute::StackProtectReq)
+    .Case("sspstrong", Attribute::StackProtectStrong)
+    .Case("uwtable", Attribute::UWTable)
+    .Default(Attribute::None);
+}
+
+/// If F has any forced attributes given on the command line, add them.
+static bool addForcedAttributes(Function *F) {
+  bool Changed = false;
+  for (auto &S : ForceAttributes) {
+    auto KV = StringRef(S).split(':');
+    if (KV.first != F->getName())
+      continue;
+
+    auto Kind = parseAttrKind(KV.second);
+    if (Kind == Attribute::None) {
+      DEBUG(dbgs() << "ForcedAttribute: " << KV.second
+                   << " unknown or not handled!\n");
+      continue;
+    }
+    if (F->hasFnAttribute(Kind))
+      continue;
+    Changed = true;
+    F->addFnAttr(Kind);
+  }
+  return Changed;
+}
+
 bool FunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
   TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
   bool Changed = false;
@@ -1878,6 +1944,7 @@ bool FunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
     if (F->isDeclaration())
       Changed |= inferPrototypeAttributes(*F, *TLI);
 
+    Changed |= addForcedAttributes(F);
     SCCNodes.insert(F);
   }
 
diff --git a/llvm/test/Transforms/FunctionAttrs/forced.ll b/llvm/test/Transforms/FunctionAttrs/forced.ll
new file mode 100644
index 000000000000..d0bdb155a20c
--- /dev/null
+++ b/llvm/test/Transforms/FunctionAttrs/forced.ll
@@ -0,0 +1,12 @@
+; RUN: opt < %s -S -functionattrs | FileCheck %s --check-prefix=CHECK-CONTROL
+; RUN: opt < %s -S -functionattrs -force-attribute foo:noinline | FileCheck %s --check-prefix=CHECK-FOO
+
+; CHECK-CONTROL: define void @foo() #0 {
+; CHECK-FOO: define void @foo() #0 {
+define void @foo() {
+  ret void
+}
+
+
+; CHECK-CONTROL: attributes #0 = { norecurse readnone }
+; CHECK-FOO: attributes #0 = { noinline norecurse readnone }