[PATCH] GlobalOpt: Apply fastcc to internal x86_thiscallcc functions

[Reid Kleckner]

Hi nlewycky,

There's no real reason we shouldn't be doing this, so far as I know.

http://llvm-reviews.chandlerc.com/D2705

Files:
  lib/Transforms/IPO/GlobalOpt.cpp
  test/Transforms/GlobalOpt/fastcc.ll

Index: lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- lib/Transforms/IPO/GlobalOpt.cpp
+++ lib/Transforms/IPO/GlobalOpt.cpp
@@ -1898,6 +1898,15 @@
   }
 }
 
+/// Return true if this is a calling convention that we'd like to change.  The
+/// idea here is that we don't want to mess with the convention if the user
+/// explicitly requested something interesting like coldcc, GHC, or anyregcc.
+static bool shouldTransformCC(Function *F) {
+  CallingConv::ID CC = F->getCallingConv();
+  // FIXME: Is it worth transforming x86_stdcallcc and x86_fastcallcc?
+  return CC == CallingConv::C || CC == CallingConv::X86_ThisCall;
+}
+
 bool GlobalOpt::OptimizeFunctions(Module &M) {
   bool Changed = false;
   // Optimize functions.
@@ -1912,11 +1921,10 @@
       Changed = true;
       ++NumFnDeleted;
     } else if (F->hasLocalLinkage()) {
-      if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
-          !F->hasAddressTaken()) {
-        // If this function has C calling conventions, is not a varargs
-        // function, and is only called directly, promote it to use the Fast
-        // calling convention.
+      if (shouldTransformCC(F) && !F->isVarArg() && !F->hasAddressTaken()) {
+        // If this function has a calling convention worth changing, is not a
+        // varargs function, and is only called directly, promote it to use the
+        // Fast calling convention.
         F->setCallingConv(CallingConv::Fast);
         ChangeCalleesToFastCall(F);
         ++NumFastCallFns;
Index: test/Transforms/GlobalOpt/fastcc.ll
===================================================================
--- /dev/null
+++ test/Transforms/GlobalOpt/fastcc.ll
@@ -0,0 +1,34 @@
+; RUN: opt < %s -globalopt -S | FileCheck %s
+
+define internal i32 @f(i32* %m) {
+; CHECK-LABEL: define internal fastcc i32 @f
+  %v = load i32* %m
+  ret i32 %v
+}
+
+define internal x86_thiscallcc i32 @g(i32* %m) {
+; CHECK-LABEL: define internal fastcc i32 @g
+  %v = load i32* %m
+  ret i32 %v
+}
+
+; Leave this one alone, because the user went out of their way to request this
+; convention.
+define internal coldcc i32 @h(i32* %m) {
+; CHECK-LABEL: define internal coldcc i32 @h
+  %v = load i32* %m
+  ret i32 %v
+}
+
+define void @call_things() {
+  %m = alloca i32
+  call i32 @f(i32* %m)
+  call x86_thiscallcc i32 @g(i32* %m)
+  call coldcc i32 @h(i32* %m)
+  ret void
+}
+
+; CHECK-LABEL: define void @call_things()
+; CHECK: call fastcc i32 @f
+; CHECK: call fastcc i32 @g
+; CHECK: call coldcc i32 @h
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