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X86ISelLowering: Support tail calls to/from callee pop functions
This enables tail calls with thiscall, stdcall, vectorcall and fastcall functions. Differential Revision: http://reviews.llvm.org/D13999 llvm-svn: 251190
This commit is contained in:
Hans Wennborg
parent
018ed97e7f
commit
c534071ad7
@ -2475,15 +2475,22 @@ static bool canGuaranteeTCO(CallingConv::ID CC) {
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CC == CallingConv::HiPE || CC == CallingConv::HHVM);
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}
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/// \brief Return true if the calling convention is a C calling convention.
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static bool isCCallConvention(CallingConv::ID CC) {
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return (CC == CallingConv::C || CC == CallingConv::X86_64_Win64 ||
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CC == CallingConv::X86_64_SysV);
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}
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/// Return true if we might ever do TCO for calls with this calling convention.
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static bool mayTailCallThisCC(CallingConv::ID CC) {
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return isCCallConvention(CC) || canGuaranteeTCO(CC);
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switch (CC) {
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// C calling conventions:
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case CallingConv::C:
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case CallingConv::X86_64_Win64:
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case CallingConv::X86_64_SysV:
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// Callee pop conventions:
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case CallingConv::X86_ThisCall:
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case CallingConv::X86_StdCall:
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case CallingConv::X86_VectorCall:
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case CallingConv::X86_FastCall:
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return true;
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default:
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return canGuaranteeTCO(CC);
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}
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}
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/// Return true if the function is being made into a tailcall target by
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@ -3661,21 +3668,9 @@ bool X86TargetLowering::IsEligibleForTailCallOptimization(
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if (isCalleeStructRet || isCallerStructRet)
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return false;
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// Don't do TCO when the current function is expected to clear its stack and
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// the callee's convention does not match.
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// FIXME: this is more restrictive than needed. We could produce a tailcall
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// when the stack adjustment matches. For example, with a thiscall that takes
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// only one argument.
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bool CallerPopsArgs =
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X86::isCalleePop(CallerCC, Subtarget->is64Bit(), CallerF->isVarArg(),
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/*GuaranteeTCO=*/false);
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if (CallerPopsArgs && !CCMatch)
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return false;
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// Do not sibcall optimize vararg calls unless all arguments are passed via
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// registers.
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if (isVarArg && !Outs.empty()) {
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// Optimizing for varargs on Win64 is unlikely to be safe without
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// additional testing.
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if (IsCalleeWin64 || IsCallerWin64)
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@ -3743,6 +3738,8 @@ bool X86TargetLowering::IsEligibleForTailCallOptimization(
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}
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}
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unsigned StackArgsSize = 0;
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// If the callee takes no arguments then go on to check the results of the
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// call.
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if (!Outs.empty()) {
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@ -3757,10 +3754,9 @@ bool X86TargetLowering::IsEligibleForTailCallOptimization(
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CCInfo.AllocateStack(32, 8);
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CCInfo.AnalyzeCallOperands(Outs, CC_X86);
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if (CCInfo.getNextStackOffset()) {
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if (MF.getInfo<X86MachineFunctionInfo>()->getBytesToPopOnReturn())
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return false;
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StackArgsSize = CCInfo.getNextStackOffset();
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if (CCInfo.getNextStackOffset()) {
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// Check if the arguments are already laid out in the right way as
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// the caller's fixed stack objects.
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MachineFrameInfo *MFI = MF.getFrameInfo();
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@ -3811,6 +3807,21 @@ bool X86TargetLowering::IsEligibleForTailCallOptimization(
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}
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}
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bool CalleeWillPop =
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X86::isCalleePop(CalleeCC, Subtarget->is64Bit(), isVarArg,
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MF.getTarget().Options.GuaranteedTailCallOpt);
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if (unsigned BytesToPop =
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MF.getInfo<X86MachineFunctionInfo>()->getBytesToPopOnReturn()) {
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// If we have bytes to pop, the callee must pop them.
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bool CalleePopMatches = CalleeWillPop && BytesToPop == StackArgsSize;
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if (!CalleePopMatches)
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return false;
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} else if (CalleeWillPop && StackArgsSize > 0) {
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// If we don't have bytes to pop, make sure the callee doesn't pop any.
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return false;
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}
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return true;
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}
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@ -1,5 +1,5 @@
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; RUN: llc -mtriple=i686-windows-msvc -O1 < %s | FileCheck %s
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; RUN: llc -mtriple=i686-windows-msvc -O0 < %s | FileCheck %s
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; RUN: llc -mtriple=i686-unknown-linux-gnu -O1 < %s | FileCheck %s
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; RUN: llc -mtriple=i686-unknown-linux-gnu -O0 < %s | FileCheck %s
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; The MSVC family of x86 calling conventions makes tail calls really tricky.
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; Tests of all the various combinations should live here.
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@ -14,27 +14,176 @@ define x86_thiscallcc void @thiscall_cdecl_notail(i32 %a, i32 %b, i32 %c) {
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tail call void @cdecl_void()
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ret void
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}
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; CHECK-LABEL: thiscall_cdecl_notail: # @thiscall_cdecl_notail
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; CHECK: calll _cdecl_void
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; CHECK-LABEL: thiscall_cdecl_notail
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; CHECK: calll cdecl_void
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; CHECK: retl $8
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define x86_stdcallcc void @stdcall_cdecl_notail(i32 %a, i32 %b, i32 %c) {
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tail call void @cdecl_void()
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ret void
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}
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; CHECK-LABEL: _stdcall_cdecl_notail@12: # @stdcall_cdecl_notail
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; CHECK: calll _cdecl_void
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; CHECK-LABEL: stdcall_cdecl_notail
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; CHECK: calll cdecl_void
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; CHECK: retl $12
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define x86_vectorcallcc void @vectorcall_cdecl_notail(i32 inreg %a, i32 inreg %b, i32 %c) {
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tail call void @cdecl_void()
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ret void
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}
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; CHECK-LABEL: vectorcall_cdecl_notail@@12: # @vectorcall_cdecl_notail
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; CHECK: calll _cdecl_void
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; CHECK-LABEL: vectorcall_cdecl_notail
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; CHECK: calll cdecl_void
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; CHECK: retl $4
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define x86_fastcallcc void @fastcall_cdecl_notail(i32 inreg %a, i32 inreg %b, i32 %c) {
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tail call void @cdecl_void()
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ret void
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}
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; CHECK-LABEL: @fastcall_cdecl_notail@12: # @fastcall_cdecl_notail
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; CHECK: calll _cdecl_void
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; CHECK-LABEL: fastcall_cdecl_notail
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; CHECK: calll cdecl_void
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; CHECK: retl $4
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; Tail call to/from callee pop functions can work under the right circumstances:
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declare x86_thiscallcc void @no_args_method(i8*)
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declare x86_thiscallcc void @one_arg_method(i8*, i32)
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declare x86_thiscallcc void @two_args_method(i8*, i32, i32)
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declare void @ccall_func()
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declare void @ccall_func1(i32)
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define x86_thiscallcc void @thiscall_thiscall_tail(i8* %this) {
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entry:
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tail call x86_thiscallcc void @no_args_method(i8* %this)
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ret void
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}
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; CHECK-LABEL: thiscall_thiscall_tail:
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; CHECK: jmp no_args_method
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define x86_thiscallcc void @thiscall_thiscall_tail2(i8* %this, i32 %a, i32 %b) {
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entry:
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tail call x86_thiscallcc void @two_args_method(i8* %this, i32 %a, i32 %b)
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ret void
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}
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; @two_args_method will take care of popping %a and %b from the stack for us.
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; CHECK-LABEL: thiscall_thiscall_tail2:
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; CHECK: jmp two_args_method
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define x86_thiscallcc void @thiscall_thiscall_notail(i8* %this, i32 %a, i32 %b, i32 %x) {
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entry:
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tail call x86_thiscallcc void @two_args_method(i8* %this, i32 %a, i32 %b)
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ret void
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}
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; @two_args_method would not pop %x.
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; CHECK-LABEL: thiscall_thiscall_notail:
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; CHECK: calll two_args_method
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; CHECK: retl $12
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define x86_thiscallcc void @thiscall_thiscall_notail2(i8* %this, i32 %a) {
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entry:
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tail call x86_thiscallcc void @no_args_method(i8* %this)
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ret void
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}
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; @no_args_method would not pop %x for us. Make sure this is checked even
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; when there are no arguments to the call.
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; CHECK-LABEL: thiscall_thiscall_notail2:
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; CHECK: calll no_args_method
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; CHECK: retl $4
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define void @ccall_thiscall_tail(i8* %x) {
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entry:
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tail call x86_thiscallcc void @no_args_method(i8* %x)
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ret void
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}
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; Tail calling from ccall to thiscall works.
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; CHECK-LABEL: ccall_thiscall_tail:
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; CHECK: jmp no_args_method
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define void @ccall_thiscall_notail(i8* %x, i32 %y) {
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entry:
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tail call x86_thiscallcc void @one_arg_method(i8* %x, i32 %y);
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ret void
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}
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; @one_arg_method would pop %y off the stack.
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; CHECK-LABEL: ccall_thiscall_notail:
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; CHECK: calll one_arg_method
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define x86_thiscallcc void @thiscall_ccall_tail(i8* %this) {
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entry:
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tail call void @ccall_func()
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ret void
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}
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; Tail call from thiscall to ccall works if no arguments need popping.
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; CHECK-LABEL: thiscall_ccall_tail:
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; CHECK: jmp ccall_func
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define x86_thiscallcc void @thiscall_ccall_notail(i8* %this, i32 %x) {
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entry:
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tail call void @ccall_func1(i32 %x)
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ret void
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}
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; No tail call: %x needs to be popped.
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; CHECK-LABEL: thiscall_ccall_notail:
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; CHECK: calll ccall_func1
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; CHECK: retl $4
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%S = type { i32 (...)** }
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define x86_thiscallcc void @tailcall_through_pointer(%S* %this, i32 %a) {
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entry:
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%0 = bitcast %S* %this to void (%S*, i32)***
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%vtable = load void (%S*, i32)**, void (%S*, i32)*** %0
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%1 = load void (%S*, i32)*, void (%S*, i32)** %vtable
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tail call x86_thiscallcc void %1(%S* %this, i32 %a)
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ret void
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}
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; Tail calling works through function pointers too.
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; CHECK-LABEL: tailcall_through_pointer:
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; CHECK: jmpl
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define x86_stdcallcc void @stdcall_cdecl_tail() {
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tail call void @ccall_func()
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ret void
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}
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; stdcall to cdecl works if no arguments need popping.
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; CHECK-LABEL: stdcall_cdecl_tail
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; CHECK: jmp ccall_func
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define x86_vectorcallcc void @vectorcall_cdecl_tail(i32 inreg %a, i32 inreg %b) {
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tail call void @ccall_func()
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ret void
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}
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; vectorcall to cdecl works if no arguments need popping.
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; CHECK-LABEL: vectorcall_cdecl_tail
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; CHECK: jmp ccall_func
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define x86_fastcallcc void @fastcall_cdecl_tail(i32 inreg %a, i32 inreg %b) {
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tail call void @ccall_func()
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ret void
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}
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; fastcall to cdecl works if no arguments need popping.
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; CHECK-LABEL: fastcall_cdecl_tail
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; CHECK: jmp ccall_func
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define x86_stdcallcc void @stdcall_thiscall_notail(i8* %this, i32 %a, i32 %b) {
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tail call x86_thiscallcc void @two_args_method(i8* %this, i32 %a, i32 %b)
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ret void
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}
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; two_args_method will not pop %this.
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; CHECK-LABEL: stdcall_thiscall_notail
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; CHECK: calll two_args_method
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define x86_stdcallcc void @stdcall_thiscall_tail(i32 %a, i32 %b) {
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tail call x86_thiscallcc void @two_args_method(i8* null, i32 %a, i32 %b)
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ret void
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}
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; The callee pop amounts match up.
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; CHECK-LABEL: stdcall_thiscall_tail
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; CHECK: jmp two_args_method
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declare x86_fastcallcc void @fastcall2(i32 inreg %a, i32 inreg %b)
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define void @cdecl_fastcall_tail(i32 %a, i32 %b) {
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tail call x86_fastcallcc void @fastcall2(i32 %a, i32 %b)
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ret void
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}
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; fastcall2 won't pop anything.
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; CHECK-LABEL: cdecl_fastcall_tail
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; CHECK: jmp fastcall2
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