diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp index 8779acc6a08b..16aab16d63ee 100644 --- a/llvm/lib/Target/X86/X86FrameLowering.cpp +++ b/llvm/lib/Target/X86/X86FrameLowering.cpp @@ -528,6 +528,14 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const { bool UseStackProbe = (STI.isOSWindows() && !STI.isTargetMachO()); + // The default stack probe size is 4096 if the function has no stackprobesize + // attribute. + unsigned StackProbeSize = 4096; + if (Fn->hasFnAttribute("stack-probe-size")) + Fn->getFnAttribute("stack-probe-size") + .getValueAsString() + .getAsInteger(0, StackProbeSize); + // If this is x86-64 and the Red Zone is not disabled, if we are a leaf // function, and use up to 128 bytes of stack space, don't have a frame // pointer, calls, or dynamic alloca then we do not need to adjust the @@ -705,8 +713,6 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const { // Adjust stack pointer: ESP -= numbytes. - static const size_t PageSize = 4096; - // 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 @@ -715,7 +721,7 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const { // 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 >= PageSize && UseStackProbe) { + if (NumBytes >= StackProbeSize && UseStackProbe) { const char *StackProbeSymbol; unsigned CallOp; diff --git a/llvm/test/CodeGen/X86/stack-probe-size.ll b/llvm/test/CodeGen/X86/stack-probe-size.ll new file mode 100644 index 000000000000..21482c3abded --- /dev/null +++ b/llvm/test/CodeGen/X86/stack-probe-size.ll @@ -0,0 +1,78 @@ +; This test is attempting to detect that the compiler correctly generates stack +; probe calls when the size of the local variables exceeds the specified stack +; probe size. +; +; Testing the default value of 4096 bytes makes sense, because the default +; stack probe size equals the page size (4096 bytes for all x86 targets), and +; this is unlikely to change in the future. +; +; RUN: llc < %s | FileCheck %s + +target datalayout = "e-m:w-p:32:32-i64:64-f80:32-n8:16:32-S32" +target triple = "i686-pc-windows-msvc" + +define i32 @test1() "stack-probe-size"="0" { + %buffer = alloca [4095 x i8] + + ret i32 0 + +; CHECK-LABEL: _test1: +; CHECK-NOT: subl $4095, %esp +; CHECK: movl $4095, %eax +; CHECK: calll __chkstk +} + +define i32 @test2() { + %buffer = alloca [4095 x i8] + + ret i32 0 + +; CHECK-LABEL: _test2: +; CHECK-NOT: movl $4095, %eax +; CHECK: subl $4095, %esp +; CHECK-NOT: calll __chkstk +} + +define i32 @test3() "stack-probe-size"="8192" { + %buffer = alloca [4095 x i8] + + ret i32 0 + +; CHECK-LABEL: _test3: +; CHECK-NOT: movl $4095, %eax +; CHECK: subl $4095, %esp +; CHECK-NOT: calll __chkstk +} + +define i32 @test4() "stack-probe-size"="0" { + %buffer = alloca [4096 x i8] + + ret i32 0 + +; CHECK-LABEL: _test4: +; CHECK-NOT: subl $4096, %esp +; CHECK: movl $4096, %eax +; CHECK: calll __chkstk +} + +define i32 @test5() { + %buffer = alloca [4096 x i8] + + ret i32 0 + +; CHECK-LABEL: _test5: +; CHECK-NOT: subl $4096, %esp +; CHECK: movl $4096, %eax +; CHECK: calll __chkstk +} + +define i32 @test6() "stack-probe-size"="8192" { + %buffer = alloca [4096 x i8] + + ret i32 0 + +; CGECK-LABEL: _test6: +; CGECK-NOT: movl $4096, %eax +; CGECK: subl $4096, %esp +; CGECK-NOT: calll __chkstk +}