avoid going through a stack slot to convert from fpstack to xmm reg
if we are just going to store it back anyway. This improves things
like:
double foo();
void bar(double *P) { *P = foo(); }
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45399 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 79aaaeb..598536d 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -33,7 +33,6 @@
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/ADT/SmallSet.h"
@@ -812,7 +811,6 @@
CCState CCInfo(CallingConv, isVarArg, getTargetMachine(), RVLocs);
CCInfo.AnalyzeCallResult(TheCall, RetCC_X86);
-
SmallVector<SDOperand, 8> ResultVals;
// Copy all of the result registers out of their specified physreg.
@@ -838,17 +836,50 @@
// an XMM register.
if ((X86ScalarSSEf32 && RVLocs[0].getValVT() == MVT::f32) ||
(X86ScalarSSEf64 && RVLocs[0].getValVT() == MVT::f64)) {
+ SDOperand StoreLoc;
+ const Value *SrcVal = 0;
+ int SrcValOffset = 0;
+
+ // Determine where to store the value. If the call result is directly
+ // used by a store, see if we can store directly into the location. In
+ // this case, we'll end up producing a fst + movss[load] + movss[store] to
+ // the same location, and the two movss's will be nuked as dead. This
+ // optimizes common things like "*D = atof(..)" to not need an
+ // intermediate stack slot.
+ if (SDOperand(TheCall, 0).hasOneUse() &&
+ SDOperand(TheCall, 1).hasOneUse()) {
+ // Ok, we have one use of the value and one use of the chain. See if
+ // they are the same node: a store.
+ if (StoreSDNode *N = dyn_cast<StoreSDNode>(*TheCall->use_begin())) {
+ if (N->getChain().Val == TheCall && N->getValue().Val == TheCall &&
+ !N->isVolatile() && !N->isTruncatingStore() &&
+ N->getAddressingMode() == ISD::UNINDEXED) {
+ StoreLoc = N->getBasePtr();
+ SrcVal = N->getSrcValue();
+ SrcValOffset = N->getSrcValueOffset();
+ }
+ }
+ }
+
+ // If we weren't able to optimize the result, just create a temporary
+ // stack slot.
+ if (StoreLoc.Val == 0) {
+ MachineFunction &MF = DAG.getMachineFunction();
+ int SSFI = MF.getFrameInfo()->CreateStackObject(8, 8);
+ StoreLoc = DAG.getFrameIndex(SSFI, getPointerTy());
+ }
+
// FIXME: Currently the FST is flagged to the FP_GET_RESULT. This
// shouldn't be necessary except that RFP cannot be live across
- // multiple blocks. When stackifier is fixed, they can be uncoupled.
- MachineFunction &MF = DAG.getMachineFunction();
- int SSFI = MF.getFrameInfo()->CreateStackObject(8, 8);
- SDOperand StackSlot = DAG.getFrameIndex(SSFI, getPointerTy());
+ // multiple blocks (which could happen if a select gets lowered into
+ // multiple blocks and scheduled in between them). When stackifier is
+ // fixed, they can be uncoupled.
SDOperand Ops[] = {
- Chain, RetVal, StackSlot, DAG.getValueType(RVLocs[0].getValVT()), InFlag
+ Chain, RetVal, StoreLoc, DAG.getValueType(RVLocs[0].getValVT()), InFlag
};
Chain = DAG.getNode(X86ISD::FST, MVT::Other, Ops, 5);
- RetVal = DAG.getLoad(RVLocs[0].getValVT(), Chain, StackSlot, NULL, 0);
+ RetVal = DAG.getLoad(RVLocs[0].getValVT(), Chain,
+ StoreLoc, SrcVal, SrcValOffset);
Chain = RetVal.getValue(1);
}
ResultVals.push_back(RetVal);