}
}
-/// mergeSPUpdatesUp - Merge two stack-manipulating instructions lower iterator.
+/// mergeSPUpdatesDown - Merge two stack-manipulating instructions lower iterator.
static
void mergeSPUpdatesDown(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
DL = MBB.findDebugLoc(MBBI);
// Adjust stack pointer: ESP -= numbytes.
- if (NumBytes >= 4096 && Subtarget->isTargetCygMing()) {
+
+ // Windows and cygwin/mingw require a prologue helper routine when allocating
+ // more than 4K bytes on the stack. Windows uses __chkstk and cygwin/mingw
+ // uses __alloca. __alloca and the 32-bit version of __chkstk will probe
+ // the stack and adjust the stack pointer in one go. The 64-bit version
+ // of __chkstk is only responsible for probing the stack. The 64-bit
+ // prologue is responsible for adjusting the stack pointer. Touching the
+ // stack at 4K increments is necessary to ensure that the guard pages used
+ // by the OS virtual memory manager are allocated in correct sequence.
+ if (NumBytes >= 4096 &&
+ (Subtarget->isTargetCygMing() || Subtarget->isTargetWin32())) {
// Check, whether EAX is livein for this function.
bool isEAXAlive = false;
for (MachineRegisterInfo::livein_iterator
Reg == X86::AH || Reg == X86::AL);
}
- // Function prologue calls _alloca to probe the stack when allocating more
- // than 4k bytes in one go. Touching the stack at 4K increments is necessary
- // to ensure that the guard pages used by the OS virtual memory manager are
- // allocated in correct sequence.
+
+ const char *StackProbeSymbol =
+ Subtarget->isTargetWindows() ? "_chkstk" : "_alloca";
if (!isEAXAlive) {
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(NumBytes);
BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
- .addExternalSymbol("_alloca")
+ .addExternalSymbol(StackProbeSymbol)
.addReg(StackPtr, RegState::Define | RegState::Implicit)
.addReg(X86::EFLAGS, RegState::Define | RegState::Implicit);
} else {
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(NumBytes - 4);
BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
- .addExternalSymbol("_alloca")
+ .addExternalSymbol(StackProbeSymbol)
.addReg(StackPtr, RegState::Define | RegState::Implicit)
.addReg(X86::EFLAGS, RegState::Define | RegState::Implicit);
--- /dev/null
+; RUN: llc < %s -mtriple=i686-pc-win32 | FileCheck %s -check-prefix=WIN_X32
+; RUN: llc < %s -mtriple=i686-pc-mingw32 | FileCheck %s -check-prefix=MINGW_X32
+; RUN: llc < %s -mtriple=x86_64-pc-mingw32 | FileCheck %s -check-prefix=MINGW_X64
+; RUN: llc < %s -mtriple=i386-pc-linux | FileCheck %s -check-prefix=LINUX
+
+; Windows and mingw require a prologue helper routine if more than 4096 bytes area
+; allocated on the stack. Windows uses __chkstk and mingw uses __alloca. __alloca
+; and the 32-bit version of __chkstk will probe the stack and adjust the stack pointer.
+; The 64-bit version of __chkstk is only responsible for probing the stack. The 64-bit
+; prologue is responsible for adjusting the stack pointer.
+
+; Stack allocation >= 4096 bytes will require call to __chkstk in the Windows ABI.
+define i32 @main4k() nounwind {
+entry:
+; WIN_X32: call __chkstk
+; WIN_X64: call __chkstk
+; MINGW_X32: call __alloca
+; MINGW_X64: call _alloca
+; LINUX-NOT: call __chkstk
+ %array4096 = alloca [4096 x i8], align 16 ; <[4096 x i8]*> [#uses=0]
+ ret i32 0
+}
+
+; Make sure we don't call __chkstk or __alloca when we have less than a 4096 stack
+; allocation.
+define i32 @main128() nounwind {
+entry:
+; WIN_X32: # BB#0:
+; WIN_X32-NOT: call __chkstk
+; WIN_X32: ret
+
+; WIN_X64: # BB#0:
+; WIN_X64-NOT: call __chkstk
+; WIN_X64: ret
+
+; MINGW_X64: # BB#0:
+; MINGW_X64-NOT: call _alloca
+; MINGW_X64: ret
+
+; LINUX: # BB#0:
+; LINUX-NOT: call __chkstk
+; LINUX: ret
+ %array128 = alloca [128 x i8], align 16 ; <[128 x i8]*> [#uses=0]
+ ret i32 0
+}