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Implement an annoying part of the Darwin/X86 abi: the callee of a struct

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return argument pops the hidden struct pointer if present, not the caller.

For example, in this testcase:

struct X { int D, E, F, G; };
struct X bar() {
  struct X a;
  a.D = 0;
  a.E = 1;
  a.F = 2;
  a.G = 3;
  return a;
}
void foo(struct X *P) {
  *P = bar();
}

We used to emit:

_foo:
        subl $28, %esp
        movl 32(%esp), %eax
        movl %eax, (%esp)
        call _bar
        addl $28, %esp
        ret
_bar:
        movl 4(%esp), %eax
        movl $0, (%eax)
        movl $1, 4(%eax)
        movl $2, 8(%eax)
        movl $3, 12(%eax)
        ret

This is correct on Linux/X86 but not Darwin/X86.  With this patch, we now
emit:

_foo:
        subl $28, %esp
        movl 32(%esp), %eax
        movl %eax, (%esp)
        call _bar
***     addl $24, %esp
        ret
_bar:
        movl 4(%esp), %eax
        movl $0, (%eax)
        movl $1, 4(%eax)
        movl $2, 8(%eax)
        movl $3, 12(%eax)
***     ret $4

For the record, GCC emits (which is functionally equivalent to our new code):

_bar:
        movl    4(%esp), %eax
        movl    $3, 12(%eax)
        movl    $2, 8(%eax)
        movl    $1, 4(%eax)
        movl    $0, (%eax)
        ret     $4
_foo:
        pushl   %esi
        subl    $40, %esp
        movl    48(%esp), %esi
        leal    16(%esp), %eax
        movl    %eax, (%esp)
        call    _bar
        subl    $4, %esp
        movl    16(%esp), %eax
        movl    %eax, (%esi)
        movl    20(%esp), %eax
        movl    %eax, 4(%esi)
        movl    24(%esp), %eax
        movl    %eax, 8(%esi)
        movl    28(%esp), %eax
        movl    %eax, 12(%esi)
        addl    $40, %esp
        popl    %esi
        ret

This fixes SingleSource/Benchmarks/CoyoteBench/fftbench with LLC and the
JIT, and fixes the X86-backend portion of PR729.  The CBE still needs to
be updated.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28438 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-05-23 18:50:38 +00:00
parent 80235d508e
commit 2d2970905c
2 changed files with 19 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
lib/Target/X86/X86ISelLowering.cpp
View File

@ -393,7 +393,8 @@ X86TargetLowering::LowerCallTo(SDOperand Chain, const Type *RetTy,
if (CallingConv == CallingConv::Fast && EnableFastCC)
return LowerFastCCCallTo(Chain, RetTy, isTailCall, Callee, Args, DAG);
return LowerCCCCallTo(Chain, RetTy, isVarArg, isTailCall, Callee, Args, DAG);
return LowerCCCCallTo(Chain, RetTy, isVarArg, isTailCall, CallingConv,
Callee, Args, DAG);
}
//===----------------------------------------------------------------------===//
@ -520,6 +521,12 @@ void X86TargetLowering::PreprocessCCCArguments(std::vector<SDOperand> &Args,
ReturnAddrIndex = 0; // No return address slot generated yet.
BytesToPopOnReturn = 0; // Callee pops nothing.
BytesCallerReserves = ArgOffset;
// If this is a struct return on Darwin/X86, the callee pops the hidden struct
// pointer.
if (F.getCallingConv() == CallingConv::CSRet &&
Subtarget->isTargetDarwin())
BytesToPopOnReturn = 4;
}
void X86TargetLowering::LowerCCCArguments(SDOperand Op, SelectionDAG &DAG) {
@ -551,6 +558,7 @@ void X86TargetLowering::LowerCCCArguments(SDOperand Op, SelectionDAG &DAG) {
std::pair<SDOperand, SDOperand>
X86TargetLowering::LowerCCCCallTo(SDOperand Chain, const Type *RetTy,
bool isVarArg, bool isTailCall,
unsigned CallingConv,
SDOperand Callee, ArgListTy &Args,
SelectionDAG &DAG) {
// Count how many bytes are to be pushed on the stack.
@ -704,13 +712,21 @@ X86TargetLowering::LowerCCCCallTo(SDOperand Chain, const Type *RetTy,
Chain = DAG.getNode(X86ISD::CALL, NodeTys, Ops);
InFlag = Chain.getValue(1);
// Create the CALLSEQ_END node.
unsigned NumBytesForCalleeToPush = 0;
// If this is is a call to a struct-return function on Darwin/X86, the callee
// pops the hidden struct pointer, so we have to push it back.
if (CallingConv == CallingConv::CSRet && Subtarget->isTargetDarwin())
NumBytesForCalleeToPush = 4;
NodeTys.clear();
NodeTys.push_back(MVT::Other); // Returns a chain
NodeTys.push_back(MVT::Flag); // Returns a flag for retval copy to use.
Ops.clear();
Ops.push_back(Chain);
Ops.push_back(DAG.getConstant(NumBytes, getPointerTy()));
Ops.push_back(DAG.getConstant(0, getPointerTy()));
Ops.push_back(DAG.getConstant(NumBytesForCalleeToPush, getPointerTy()));
Ops.push_back(InFlag);
Chain = DAG.getNode(ISD::CALLSEQ_END, NodeTys, Ops);
InFlag = Chain.getValue(1);

2
lib/Target/X86/X86ISelLowering.h
View File

@ -374,7 +374,7 @@ namespace llvm {
void LowerCCCArguments(SDOperand Op, SelectionDAG &DAG);
std::pair<SDOperand, SDOperand>
LowerCCCCallTo(SDOperand Chain, const Type *RetTy, bool isVarArg,
bool isTailCall,
bool isTailCall, unsigned CallingConv,
SDOperand Callee, ArgListTy &Args, SelectionDAG &DAG);
// Fast Calling Convention implementation.