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Re-apply r282920 "X86: Allow conditional tail calls in Win64 "leaf" functions (PR26302)" 

The original commit was reverted in r283329 due to a miscompile in
Chromium. That turned out to be the same issue as PR31257, which was
fixed in r295262.

llvm-svn: 295357
This commit is contained in:
Hans Wennborg 2017-02-16 19:04:42 +00:00
parent 84cd4ea301
commit 35905d6a67
3 changed files with 31 additions and 8 deletions
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5
llvm/lib/Target/X86/X86ExpandPseudo.cpp
View File

@ -122,8 +122,9 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
Op = X86::TAILJMPd_CC;
break;
case X86::TCRETURNdi64cc:
assert(!IsWin64 && "Conditional tail calls confuse the Win64 unwinder.");
// TODO: We could do it for Win64 "leaf" functions though; PR30337.
assert(!MBB.getParent()->hasWinCFI() &&
"Conditional tail calls confuse "
"the Win64 unwinder.");
Op = X86::TAILJMPd64_CC;
break;
default:

7
llvm/lib/Target/X86/X86InstrInfo.cpp
View File

@ -5817,9 +5817,9 @@ bool X86InstrInfo::canMakeTailCallConditional(
return false;
}
if (Subtarget.isTargetWin64()) {
const MachineFunction *MF = TailCall.getParent()->getParent();
if (Subtarget.isTargetWin64() && MF->hasWinCFI()) {
// Conditional tail calls confuse the Win64 unwinder.
// TODO: Allow them for "leaf" functions; PR30337.
return false;
}
@ -5829,8 +5829,7 @@ bool X86InstrInfo::canMakeTailCallConditional(
return false;
}
const X86MachineFunctionInfo *X86FI =
TailCall.getParent()->getParent()->getInfo<X86MachineFunctionInfo>();
const X86MachineFunctionInfo *X86FI = MF->getInfo<X86MachineFunctionInfo>();
if (X86FI->getTCReturnAddrDelta() != 0 ||
TailCall.getOperand(1).getImm() != 0) {
// A conditional tail call cannot do any stack adjustment.

27
llvm/test/CodeGen/X86/conditional-tailcall.ll
View File

@ -1,5 +1,6 @@
; RUN: llc < %s -mtriple=i686-linux -show-mc-encoding | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK32
; RUN: llc < %s -mtriple=i686-linux -show-mc-encoding | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK32
; RUN: llc < %s -mtriple=x86_64-linux -show-mc-encoding | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK64
; RUN: llc < %s -mtriple=x86_64-win32 -show-mc-encoding | FileCheck %s --check-prefix=CHECK --check-prefix=WIN64
declare void @foo()
declare void @bar()
@ -23,6 +24,28 @@ bb2:
; CHECK: jmp foo
}
define void @f_non_leaf(i32 %x, i32 %y) optsize {
entry:
; Force %ebx to be spilled on the stack, turning this into
; not a "leaf" function for Win64.
tail call void asm sideeffect "", "~{ebx}"()
%p = icmp eq i32 %x, %y
br i1 %p, label %bb1, label %bb2
bb1:
tail call void @foo()
ret void
bb2:
tail call void @bar()
ret void
; CHECK-LABEL: f_non_leaf:
; WIN64-NOT: je foo
; WIN64-NOT: jne bar
; WIN64: jne
; WIN64: jmp foo
; WIN64: jmp bar
}
declare x86_thiscallcc zeroext i1 @baz(i8*, i32)
define x86_thiscallcc zeroext i1 @BlockPlacementTest(i8* %this, i32 %x) optsize {
@ -111,7 +134,7 @@ sw.bb22: ; preds = %for.body
; Make sure Machine Copy Propagation doesn't delete the mov to %ecx becaue it
; thinks the conditional tail call clobbers it.
; CHECK64-LABEL: .LBB2_11:
; CHECK64-LABEL: .LBB3_11:
; CHECK64: movzbl (%rdi), %ecx
; CHECK64-NEXT: addl $-48, %ecx
; CHECK64-NEXT: cmpl $10, %ecx