[llvm-commits] [llvm] r45399 - in /llvm/trunk: lib/Target/X86/README.txt lib/Target/X86/X86ISelLowering.cpp test/CodeGen/X86/fp-stack-ret-store.ll
Chris Lattner
sabre at nondot.org
Fri Dec 28 22:41:28 PST 2007
Author: lattner
Date: Sat Dec 29 00:41:28 2007
New Revision: 45399
URL: http://llvm.org/viewvc/llvm-project?rev=45399&view=rev
Log:
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(); }
Added:
llvm/trunk/test/CodeGen/X86/fp-stack-ret-store.ll
Modified:
llvm/trunk/lib/Target/X86/README.txt
llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
Modified: llvm/trunk/lib/Target/X86/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/README.txt?rev=45399&r1=45398&r2=45399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Sat Dec 29 00:41:28 2007
@@ -1636,24 +1636,3 @@
This would result in smaller code and more efficient microops.
//===---------------------------------------------------------------------===//
-
-We should be smarter about conversion from fpstack to XMM regs.
-
-double foo();
-void bar(double *P) { *P = foo(); }
-
-We compile that to:
-
-_bar:
- subl $12, %esp
- call L_foo$stub
- fstpl (%esp)
- movl 16(%esp), %eax
- movsd (%esp), %xmm0
- movsd %xmm0, (%eax)
- addl $12, %esp
- ret
-
-for example. The magic to/from the stack is unneeded.
-
-//===---------------------------------------------------------------------===//
Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=45399&r1=45398&r2=45399&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Sat Dec 29 00:41:28 2007
@@ -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);
Added: llvm/trunk/test/CodeGen/X86/fp-stack-ret-store.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/fp-stack-ret-store.ll?rev=45399&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/fp-stack-ret-store.ll (added)
+++ llvm/trunk/test/CodeGen/X86/fp-stack-ret-store.ll Sat Dec 29 00:41:28 2007
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | llc | not grep movss
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i686-apple-darwin8"
+
+; This should store directly into P from the FP stack. It should not
+; go through a stack slot to get there.
+
+define void @bar(double* %P) {
+entry:
+ %tmp = tail call double (...)* @foo( ) ; <double> [#uses=1]
+ store double %tmp, double* %P, align 8
+ ret void
+}
+
+declare double @foo(...)
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