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[WebAssembly] Don't stackify calls past stack pointer modifications. 

llvm-svn: 269843
This commit is contained in:
Dan Gohman 2016-05-17 21:14:26 +00:00
parent 096ccdd389
commit d08cd15f33
3 changed files with 56 additions and 21 deletions
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16
llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
View File

@ -82,7 +82,8 @@ static void writeSPToMemory(unsigned SrcReg, MachineFunction &MF,
MachineBasicBlock::iterator &InsertAddr,
MachineBasicBlock::iterator &InsertStore,
DebugLoc DL) {
auto *SPSymbol = MF.createExternalSymbolName("__stack_pointer");
const char *ES = "__stack_pointer";
auto *SPSymbol = MF.createExternalSymbolName(ES);
MachineRegisterInfo &MRI = MF.getRegInfo();
const TargetRegisterClass *PtrRC =
MRI.getTargetRegisterInfo()->getPointerRegClass(MF);
@ -92,7 +93,8 @@ static void writeSPToMemory(unsigned SrcReg, MachineFunction &MF,
BuildMI(MBB, InsertAddr, DL, TII->get(WebAssembly::CONST_I32), SPAddr)
.addExternalSymbol(SPSymbol);
auto *MMO = new MachineMemOperand(MachinePointerInfo(),
auto *MMO = new MachineMemOperand(MachinePointerInfo(MF.getPSVManager()
.getExternalSymbolCallEntry(ES)),
MachineMemOperand::MOStore, 4, 4);
BuildMI(MBB, InsertStore, DL, TII->get(WebAssembly::STORE_I32),
Discard)
@ -138,14 +140,12 @@ void WebAssemblyFrameLowering::emitPrologue(MachineFunction &MF,
MRI.getTargetRegisterInfo()->getPointerRegClass(MF);
unsigned SPAddr = MRI.createVirtualRegister(PtrRC);
unsigned SPReg = MRI.createVirtualRegister(PtrRC);
auto *SPSymbol = MF.createExternalSymbolName("__stack_pointer");
const char *ES = "__stack_pointer";
auto *SPSymbol = MF.createExternalSymbolName(ES);
BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), SPAddr)
.addExternalSymbol(SPSymbol);
// This MachinePointerInfo should reference __stack_pointer as well but
// doesn't because MachinePointerInfo() takes a GV which we don't have for
// __stack_pointer. TODO: check if PseudoSourceValue::ExternalSymbolCallEntry
// is appropriate instead. (likewise for EmitEpologue below)
auto *LoadMMO = new MachineMemOperand(MachinePointerInfo(),
auto *LoadMMO = new MachineMemOperand(MachinePointerInfo(MF.getPSVManager()
.getExternalSymbolCallEntry(ES)),
MachineMemOperand::MOLoad, 4, 4);
// Load the SP value.
BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::LOAD_I32),

45
llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
View File

@ -90,7 +90,11 @@ static void ImposeStackOrdering(MachineInstr *MI) {
// MI->getOperand(CalleeOpNo) reads memory, writes memory, and/or has side
// effects.
static void QueryCallee(const MachineInstr *MI, unsigned CalleeOpNo,
bool &Read, bool &Write, bool &Effects) {
bool &Read, bool &Write, bool &Effects,
bool &StackPointer) {
// All calls can use the stack pointer.
StackPointer = true;
const MachineOperand &MO = MI->getOperand(CalleeOpNo);
if (MO.isGlobal()) {
const Constant *GV = MO.getGlobal();
@ -116,10 +120,10 @@ static void QueryCallee(const MachineInstr *MI, unsigned CalleeOpNo,
Effects = true;
}
// Determine whether MI reads memory, writes memory, and/or has side
// effects.
// Determine whether MI reads memory, writes memory, has side effects,
// and/or uses the __stack_pointer value.
static void Query(const MachineInstr *MI, AliasAnalysis &AA,
bool &Read, bool &Write, bool &Effects) {
bool &Read, bool &Write, bool &Effects, bool &StackPointer) {
assert(!MI->isPosition());
assert(!MI->isTerminator());
assert(!MI->isDebugValue());
@ -129,9 +133,21 @@ static void Query(const MachineInstr *MI, AliasAnalysis &AA,
Read = true;
// Check for stores.
if (MI->mayStore())
if (MI->mayStore()) {
Write = true;
else if (MI->hasOrderedMemoryRef()) {
// Check for stores to __stack_pointer.
for (auto MMO : MI->memoperands()) {
const MachinePointerInfo &MPI = MMO->getPointerInfo();
if (MPI.V.is<const PseudoSourceValue *>()) {
auto PSV = MPI.V.get<const PseudoSourceValue *>();
if (const ExternalSymbolPseudoSourceValue *EPSV =
dyn_cast<ExternalSymbolPseudoSourceValue>(PSV))
if (StringRef(EPSV->getSymbol()) == "__stack_pointer")
StackPointer = true;
}
}
} else if (MI->hasOrderedMemoryRef()) {
switch (MI->getOpcode()) {
case WebAssembly::DIV_S_I32: case WebAssembly::DIV_S_I64:
case WebAssembly::REM_S_I32: case WebAssembly::REM_S_I64:
@ -181,13 +197,13 @@ static void Query(const MachineInstr *MI, AliasAnalysis &AA,
if (MI->isCall()) {
switch (MI->getOpcode()) {
case WebAssembly::CALL_VOID:
QueryCallee(MI, 0, Read, Write, Effects);
QueryCallee(MI, 0, Read, Write, Effects, StackPointer);
break;
case WebAssembly::CALL_I32:
case WebAssembly::CALL_I64:
case WebAssembly::CALL_F32:
case WebAssembly::CALL_F64:
QueryCallee(MI, 1, Read, Write, Effects);
QueryCallee(MI, 1, Read, Write, Effects, StackPointer);
break;
case WebAssembly::CALL_INDIRECT_VOID:
case WebAssembly::CALL_INDIRECT_I32:
@ -197,6 +213,7 @@ static void Query(const MachineInstr *MI, AliasAnalysis &AA,
Read = true;
Write = true;
Effects = true;
StackPointer = true;
break;
default:
llvm_unreachable("unexpected call opcode");
@ -308,12 +325,12 @@ static bool IsSafeToMove(const MachineInstr *Def, const MachineInstr *Insert,
return false;
}
bool Read = false, Write = false, Effects = false;
Query(Def, AA, Read, Write, Effects);
bool Read = false, Write = false, Effects = false, StackPointer = false;
Query(Def, AA, Read, Write, Effects, StackPointer);
// If the instruction does not access memory and has no side effects, it has
// no additional dependencies.
if (!Read && !Write && !Effects)
if (!Read && !Write && !Effects && !StackPointer)
return true;
// Scan through the intervening instructions between Def and Insert.
@ -322,13 +339,17 @@ static bool IsSafeToMove(const MachineInstr *Def, const MachineInstr *Insert,
bool InterveningRead = false;
bool InterveningWrite = false;
bool InterveningEffects = false;
Query(I, AA, InterveningRead, InterveningWrite, InterveningEffects);
bool InterveningStackPointer = false;
Query(I, AA, InterveningRead, InterveningWrite, InterveningEffects,
InterveningStackPointer);
if (Effects && InterveningEffects)
return false;
if (Read && InterveningWrite)
return false;
if (Write && (InterveningRead || InterveningWrite))
return false;
if (StackPointer && InterveningStackPointer)
return false;
}
return true;

16
llvm/test/CodeGen/WebAssembly/reg-stackify.ll
View File

@ -402,7 +402,7 @@ define i32 @no_stackify_past_epilogue() {
; Stackify a loop induction variable into a loop comparison.
; CHECK_LABEL: stackify_indvar:
; CHECK-LABEL: stackify_indvar:
; CHECK: i32.const $push[[L5:.+]]=, 1{{$}}
; CHECK-NEXT: i32.add $push[[L4:.+]]=, $[[R0:.+]], $pop[[L5]]{{$}}
; CHECK-NEXT: tee_local $push[[L3:.+]]=, $[[R0]]=, $pop[[L4]]{{$}}
@ -424,6 +424,20 @@ bb10: ; preds = %bb9, %bb
ret void
}
; Don't stackify a call past a __stack_pointer store.
; CHECK-LABEL: stackpointer_dependency:
; CHECK: call {{.+}}, stackpointer_callee@FUNCTION,
; CHECK: i32.const $push[[L0:.+]]=, __stack_pointer
; CHECK-NEXT: i32.store $discard=, 0($pop[[L0]]),
declare i32 @stackpointer_callee(i8* readnone, i8* readnone)
declare i8* @llvm.frameaddress(i32)
define i32 @stackpointer_dependency(i8* readnone) {
%2 = tail call i8* @llvm.frameaddress(i32 0)
%3 = tail call i32 @stackpointer_callee(i8* %0, i8* %2)
ret i32 %3
}
!llvm.module.flags = !{!0}
!llvm.dbg.cu = !{!1}