Implement an x86-64 ABI detail of passing structs by hidden first
argument. The x86-64 ABI requires the incoming value of %rdi to
be copied to %rax on exit from a function that is returning a
large C struct.
Also, add a README-X86-64 entry detailing the missed optimization
opportunity and proposing an alternative approach.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50075 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86MachineFunctionInfo.h b/lib/Target/X86/X86MachineFunctionInfo.h
index fcdeb05..b5c9caf 100644
--- a/lib/Target/X86/X86MachineFunctionInfo.h
+++ b/lib/Target/X86/X86MachineFunctionInfo.h
@@ -53,20 +53,27 @@
/// the returnaddr can be savely move to this area
int TailCallReturnAddrDelta;
+ /// SRetReturnReg - Some subtargets require that sret lowering includes
+ /// returning the value of the returned struct in a register. This field
+ /// holds the virtual register into which the sret argument is passed.
+ unsigned SRetReturnReg;
+
public:
X86MachineFunctionInfo() : ForceFramePointer(false),
CalleeSavedFrameSize(0),
BytesToPopOnReturn(0),
DecorationStyle(None),
ReturnAddrIndex(0),
- TailCallReturnAddrDelta(0) {}
+ TailCallReturnAddrDelta(0),
+ SRetReturnReg(0) {}
X86MachineFunctionInfo(MachineFunction &MF) : ForceFramePointer(false),
CalleeSavedFrameSize(0),
BytesToPopOnReturn(0),
DecorationStyle(None),
ReturnAddrIndex(0),
- TailCallReturnAddrDelta(0) {}
+ TailCallReturnAddrDelta(0),
+ SRetReturnReg(0) {}
bool getForceFramePointer() const { return ForceFramePointer;}
void setForceFramePointer(bool forceFP) { ForceFramePointer = forceFP; }
@@ -85,6 +92,9 @@
int getTCReturnAddrDelta() const { return TailCallReturnAddrDelta; }
void setTCReturnAddrDelta(int delta) {TailCallReturnAddrDelta = delta;}
+
+ unsigned getSRetReturnReg() const { return SRetReturnReg; }
+ void setSRetReturnReg(unsigned Reg) { SRetReturnReg = Reg; }
};
} // End llvm namespace