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GlobalOpt: Apply fastcc to internal x86_thiscallcc functions

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We should apply fastcc whenever profitable.  We can expand this list,
but there are lots of conventions with performance implications that we
don't want to change.

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202293 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Kleckner
2014-02-26 19:57:30 +00:00
parent 0a91f48308
commit 726bae9a66
2 changed files with 60 additions and 5 deletions
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19
lib/Transforms/IPO/GlobalOpt.cpp
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@@ -1902,6 +1902,16 @@ static void RemoveNestAttribute(Function *F) {
}
}
/// 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 with performance implications like coldcc,
/// GHC, or anyregcc.
static bool isProfitableToMakeFastCC(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.
@@ -1916,11 +1926,10 @@ bool GlobalOpt::OptimizeFunctions(Module &M) {
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 (isProfitableToMakeFastCC(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;