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[X86] Clarify some stackmap shadow optimization code as based on review

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feedback from Eric Christopher.

No functional change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213917 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Lang Hames 2014-07-25 02:29:19 +00:00
parent 2286ae542c
commit 76cbffa2a9
2 changed files with 19 additions and 7 deletions
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15
lib/Target/X86/X86AsmPrinter.h
View File

@ -44,16 +44,27 @@ class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
~StackMapShadowTracker();
void startFunction(MachineFunction &MF);
void count(MCInst &Inst, const MCSubtargetInfo &STI);
// Called to signal the start of a shadow of RequiredSize bytes.
void reset(unsigned RequiredSize) {
RequiredShadowSize = RequiredSize;
CurrentShadowSize = 0;
Count = true;
InShadow = true;
}
// Called before every stackmap/patchpoint, and at the end of basic blocks,
// to emit any necessary padding-NOPs.
void emitShadowPadding(MCStreamer &OutStreamer, const MCSubtargetInfo &STI);
private:
TargetMachine &TM;
std::unique_ptr<MCCodeEmitter> CodeEmitter;
bool Count;
bool InShadow;
// RequiredShadowSize holds the length of the shadow specified in the most
// recently encountered STACKMAP instruction.
// CurrentShadowSize counts the number of bytes encoded since the most
// recently encountered STACKMAP, stopping when that number is greater than
// or equal to RequiredShadowSize.
unsigned RequiredShadowSize, CurrentShadowSize;
};

11
lib/Target/X86/X86MCInstLower.cpp
View File

@ -66,7 +66,7 @@ static void EmitNops(MCStreamer &OS, unsigned NumBytes, bool Is64Bit,
namespace llvm {
X86AsmPrinter::StackMapShadowTracker::StackMapShadowTracker(TargetMachine &TM)
: TM(TM), Count(false), RequiredShadowSize(0), CurrentShadowSize(0) {}
: TM(TM), InShadow(false), RequiredShadowSize(0), CurrentShadowSize(0) {}
X86AsmPrinter::StackMapShadowTracker::~StackMapShadowTracker() {}
@ -80,7 +80,7 @@ namespace llvm {
void X86AsmPrinter::StackMapShadowTracker::count(MCInst &Inst,
const MCSubtargetInfo &STI) {
if (Count) {
if (InShadow) {
SmallString<256> Code;
SmallVector<MCFixup, 4> Fixups;
raw_svector_ostream VecOS(Code);
@ -88,16 +88,17 @@ namespace llvm {
VecOS.flush();
CurrentShadowSize += Code.size();
if (CurrentShadowSize >= RequiredShadowSize)
Count = false; // The shadow is big enough. Stop counting.
InShadow = false; // The shadow is big enough. Stop counting.
}
}
void X86AsmPrinter::StackMapShadowTracker::emitShadowPadding(
MCStreamer &OutStreamer, const MCSubtargetInfo &STI) {
if (Count && CurrentShadowSize < RequiredShadowSize)
if (InShadow && CurrentShadowSize < RequiredShadowSize) {
InShadow = false;
EmitNops(OutStreamer, RequiredShadowSize - CurrentShadowSize,
TM.getSubtarget<X86Subtarget>().is64Bit(), STI);
Count = false;
}
}
void X86AsmPrinter::EmitAndCountInstruction(MCInst &Inst) {