maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[WebAssembly] Remove TEEs when dests are unstackified 

When created in RegStackify pass, `TEE` has two destinations, where
op0 is stackified and op1 is not. But it is possible that
op0 becomes unstackified in `fixUnwindMismatches` function in
CFGStackify pass when a nested try-catch-end is introduced, violating
the invariant of `TEE`s destinations.

In this case we convert the `TEE` into two `COPY`s, which will
eventually be resolved in ExplicitLocals.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D81851
This commit is contained in:
Heejin Ahn 2020-06-15 09:31:19 -07:00
parent 63700971ac
commit 83c26eae23
2 changed files with 131 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
View File

@ -733,12 +733,30 @@ void WebAssemblyCFGStackify::removeUnnecessaryInstrs(MachineFunction &MF) {
}
}
// Get the appropriate copy opcode for the given register class.
static unsigned getCopyOpcode(const TargetRegisterClass *RC) {
if (RC == &WebAssembly::I32RegClass)
return WebAssembly::COPY_I32;
if (RC == &WebAssembly::I64RegClass)
return WebAssembly::COPY_I64;
if (RC == &WebAssembly::F32RegClass)
return WebAssembly::COPY_F32;
if (RC == &WebAssembly::F64RegClass)
return WebAssembly::COPY_F64;
if (RC == &WebAssembly::V128RegClass)
return WebAssembly::COPY_V128;
if (RC == &WebAssembly::EXNREFRegClass)
return WebAssembly::COPY_EXNREF;
llvm_unreachable("Unexpected register class");
}
// When MBB is split into MBB and Split, we should unstackify defs in MBB that
// have their uses in Split.
static void unstackifyVRegsUsedInSplitBB(MachineBasicBlock &MBB,
MachineBasicBlock &Split,
WebAssemblyFunctionInfo &MFI,
MachineRegisterInfo &MRI) {
MachineRegisterInfo &MRI,
const WebAssemblyInstrInfo &TII) {
for (auto &MI : Split) {
for (auto &MO : MI.explicit_uses()) {
if (!MO.isReg() || Register::isPhysicalRegister(MO.getReg()))
@ -748,6 +766,47 @@ static void unstackifyVRegsUsedInSplitBB(MachineBasicBlock &MBB,
MFI.unstackifyVReg(MO.getReg());
}
}
// In RegStackify, when a register definition is used multiple times,
// Reg = INST ...
// INST ..., Reg, ...
// INST ..., Reg, ...
// INST ..., Reg, ...
//
// we introduce a TEE, which has the following form:
// DefReg = INST ...
// TeeReg, Reg = TEE_... DefReg
// INST ..., TeeReg, ...
// INST ..., Reg, ...
// INST ..., Reg, ...
// with DefReg and TeeReg stackified but Reg not stackified.
//
// But the invariant that TeeReg should be stackified can be violated while we
// unstackify registers in the split BB above. In this case, we convert TEEs
// into two COPYs. This COPY will be eventually eliminated in ExplicitLocals.
// DefReg = INST ...
// TeeReg = COPY DefReg
// Reg = COPY DefReg
// INST ..., TeeReg, ...
// INST ..., Reg, ...
// INST ..., Reg, ...
for (auto I = MBB.begin(), E = MBB.end(); I != E;) {
MachineInstr &MI = *I++;
if (!WebAssembly::isTee(MI.getOpcode()))
continue;
Register TeeReg = MI.getOperand(0).getReg();
Register Reg = MI.getOperand(1).getReg();
Register DefReg = MI.getOperand(2).getReg();
if (!MFI.isVRegStackified(TeeReg)) {
// Now we are not using TEE anymore, so unstackify DefReg too
MFI.unstackifyVReg(DefReg);
unsigned CopyOpc = getCopyOpcode(MRI.getRegClass(DefReg));
BuildMI(MBB, &MI, MI.getDebugLoc(), TII.get(CopyOpc), TeeReg)
.addReg(DefReg);
BuildMI(MBB, &MI, MI.getDebugLoc(), TII.get(CopyOpc), Reg).addReg(DefReg);
MI.eraseFromParent();
}
}
}
bool WebAssemblyCFGStackify::fixUnwindMismatches(MachineFunction &MF) {
@ -1068,7 +1127,7 @@ bool WebAssemblyCFGStackify::fixUnwindMismatches(MachineFunction &MF) {
BrDest->insert(BrDest->end(), EndTry->removeFromParent());
// Take out the handler body from EH pad to the new branch destination BB.
BrDest->splice(BrDest->end(), EHPad, SplitPos, EHPad->end());
unstackifyVRegsUsedInSplitBB(*EHPad, *BrDest, MFI, MRI);
unstackifyVRegsUsedInSplitBB(*EHPad, *BrDest, MFI, MRI, TII);
// Fix predecessor-successor relationship.
BrDest->transferSuccessors(EHPad);
EHPad->addSuccessor(BrDest);
@ -1206,7 +1265,7 @@ bool WebAssemblyCFGStackify::fixUnwindMismatches(MachineFunction &MF) {
// new nested continuation BB.
NestedCont->splice(NestedCont->end(), MBB,
std::next(RangeEnd->getIterator()), MBB->end());
unstackifyVRegsUsedInSplitBB(*MBB, *NestedCont, MFI, MRI);
unstackifyVRegsUsedInSplitBB(*MBB, *NestedCont, MFI, MRI, TII);
registerTryScope(NestedTry, NestedEndTry, NestedEHPad);
// Fix predecessor-successor relationship.

97
llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
View File

@ -3,6 +3,7 @@
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -exception-model=wasm -mattr=+exception-handling
; RUN: llc < %s -O0 -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -verify-machineinstrs -exception-model=wasm -mattr=+exception-handling | FileCheck %s --check-prefix=NOOPT
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -exception-model=wasm -mattr=+exception-handling -wasm-disable-ehpad-sort | FileCheck %s --check-prefix=NOSORT
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -exception-model=wasm -mattr=+exception-handling -wasm-disable-ehpad-sort | FileCheck %s --check-prefix=NOSORT-LOCALS
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -exception-model=wasm -mattr=+exception-handling -wasm-disable-ehpad-sort -stats 2>&1 | FileCheck %s --check-prefix=NOSORT-STAT
target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
@ -533,16 +534,56 @@ try.cont: ; preds = %catch.start0
ret i32 0
}
; Tests the case when TEE stackifies a register in RegStackify but it gets
; unstackified in fixUnwindMismatches in CFGStackify.
; NOSORT-LOCALS-LABEL: test8
define void @test8(i32 %x) personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
bb0:
invoke void @foo()
to label %bb1 unwind label %catch.dispatch0
bb1: ; preds = %bb0
%t = add i32 %x, 4
; This %addr is used in multiple places, so tee is introduced in RegStackify,
; which stackifies the use of %addr in store instruction. A tee has two dest
; registers, the first of which is stackified and the second is not.
; But when we introduce a nested try-catch in fixUnwindMismatches in
; CFGStackify, it is possible that we end up unstackifying the first dest
; register. In that case, we convert that tee into a copy.
%addr = inttoptr i32 %t to i32*
%load = load i32, i32* %addr
%call = call i32 @baz()
%add = add i32 %load, %call
store i32 %add, i32* %addr
ret void
; NOSORT-LOCALS: i32.add
; NOSORT-LOCALS-NOT: local.tee
; NOSORT-LOCALS-NEXT: local.set
catch.dispatch0: ; preds = %bb0
%0 = catchswitch within none [label %catch.start0] unwind to caller
catch.start0: ; preds = %catch.dispatch0
%1 = catchpad within %0 [i8* null]
%2 = call i8* @llvm.wasm.get.exception(token %1)
%3 = call i32 @llvm.wasm.get.ehselector(token %1)
catchret from %1 to label %try.cont
try.cont: ; preds = %catch.start0
ret void
}
; If not for the unwind destination mismatch, the LOOP marker here would have an
; i32 signature. But because we add a rethrow instruction at the end of the
; appendix block, now the LOOP marker does not have a signature (= has a void
; signature). Here the two calls two 'bar' are supposed to throw up to the
; caller, but incorrectly unwind to 'catch19' after linearizing the CFG.
; NOSORT-LABEL: test8
; NOSORT-LABEL: test9
; NOSORT: block
; NOSORT-NOT: loop i32
; NOSORT: loop # label40:
; NOSORT: loop # label42:
; NOSORT: try
; NOSORT: call foo
; --- Nested try/catch/end_try starts
@ -550,18 +591,18 @@ try.cont: ; preds = %catch.start0
; NOSORT: call bar
; NOSORT: call bar
; NOSORT: catch $[[REG:[0-9]+]]=
; NOSORT: br 1 # 1: down to label41
; NOSORT: br 1 # 1: down to label43
; NOSORT: end_try
; --- Nested try/catch/end_try ends
; NOSORT: return {{.*}}
; NOSORT: catch $drop= # catch21:
; NOSORT: br 1 # 1: up to label40
; NOSORT: end_try # label41:
; NOSORT: catch $drop= # catch23:
; NOSORT: br 1 # 1: up to label42
; NOSORT: end_try # label43:
; NOSORT: end_loop
; NOSORT: end_block
; NOSORT: rethrow $[[REG]] # to caller
define i32 @test8(i32* %p) personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
define i32 @test9(i32* %p) personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
entry:
store volatile i32 0, i32* %p
br label %loop
@ -595,7 +636,7 @@ try.cont: ; preds = %catch.start
; - A may-throw instruction unwinds to an incorrect EH pad after linearizing the
; CFG, when it is supposed to unwind to the caller.
; NOSORT-LABEL: test9
; NOSORT-LABEL: test10
; NOSORT: block
; NOSORT: block
; NOSORT: try
@ -605,40 +646,40 @@ try.cont: ; preds = %catch.start
; NOSORT: try
; NOSORT: call bar
; NOSORT: catch $[[REG0:[0-9]+]]=
; NOSORT: br 2 # 2: down to label45
; NOSORT: br 2 # 2: down to label47
; NOSORT: end_try
; --- Nested try/catch/end_try ends
; NOSORT: br 2 # 2: down to label44
; NOSORT: br 2 # 2: down to label46
; NOSORT: catch {{.*}}
; NOSORT: block i32
; NOSORT: br_on_exn 0, {{.*}} # 0: down to label48
; NOSORT: br_on_exn 0, {{.*}} # 0: down to label50
; --- Nested try/catch/end_try starts
; NOSORT: try
; NOSORT: rethrow {{.*}} # down to catch26
; NOSORT: catch $[[REG1:[0-9]+]]= # catch26:
; NOSORT: br 5 # 5: down to label43
; NOSORT: rethrow {{.*}} # down to catch28
; NOSORT: catch $[[REG1:[0-9]+]]= # catch28:
; NOSORT: br 5 # 5: down to label45
; NOSORT: end_try
; --- Nested try/catch/end_try ends
; NOSORT: end_block # label48:
; NOSORT: end_block # label50:
; NOSORT: call $drop=, __cxa_begin_catch
; --- Nested try/catch/end_try starts
; NOSORT: try
; NOSORT: call __cxa_end_catch
; NOSORT: catch $[[REG1]]=
; NOSORT: br 4 # 4: down to label43
; NOSORT: br 4 # 4: down to label45
; NOSORT: end_try
; --- Nested try/catch/end_try ends
; NOSORT: br 2 # 2: down to label44
; NOSORT: br 2 # 2: down to label46
; NOSORT: end_try
; NOSORT: catch $[[REG0]]=
; NOSORT: end_try # label45:
; NOSORT: end_try # label47:
; NOSORT: call $drop=, __cxa_begin_catch
; NOSORT: call __cxa_end_catch
; NOSORT: end_block # label44:
; NOSORT: end_block # label46:
; NOSORT: return
; NOSORT: end_block # label43:
; NOSORT: end_block # label45:
; NOSORT: rethrow $[[REG1]] # to caller
define void @test9() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
define void @test10() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
bb0:
invoke void @foo()
to label %bb1 unwind label %catch.dispatch0
@ -688,7 +729,7 @@ try.cont: ; preds = %catch.start1, %catc
; NOOPT: call foo
; NOOPT: end_block
; NOOPT: return
define void @test10(i32 %arg) personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
define void @test11(i32 %arg) personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
entry:
%tobool = icmp ne i32 %arg, 0
br i1 %tobool, label %if.then, label %if.end
@ -725,7 +766,7 @@ if.end: ; preds = %cont, %catch.start,
; invoke.cont BB fall within try~end_try, but they shouldn't cause crashes or
; unwinding destination mismatches in CFGStackify.
; NOSORT-LABEL: test11
; NOSORT-LABEL: test12
; NOSORT: try
; NOSORT: call foo
; NOSORT: call {{.*}} memcpy
@ -735,7 +776,7 @@ if.end: ; preds = %cont, %catch.start,
; NOSORT: catch
; NOSORT: rethrow
; NOSORT: end_try
define void @test11(i8* %a, i8* %b) personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
define void @test12(i8* %a, i8* %b) personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
entry:
%o = alloca %class.Object, align 1
invoke void @foo()
@ -759,11 +800,11 @@ ehcleanup: ; preds = %entry
; 'nothrow_i32' and 'fun', because the return value of 'nothrow_i32' is
; stackified and pushed onto the stack to be consumed by the call to 'fun'.
; CHECK-LABEL: test12
; CHECK-LABEL: test13
; CHECK: try
; CHECK: call $push{{.*}}=, nothrow_i32
; CHECK: call fun, $pop{{.*}}
define void @test12() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
define void @test13() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
entry:
%call = call i32 @nothrow_i32()
invoke void @fun(i32 %call)
@ -784,7 +825,7 @@ terminate: ; preds = %entry
; This crashed on debug mode (= when NDEBUG is not defined) when the logic for
; computing the innermost region was not correct, in which a loop region
; contains an exception region. This should pass CFGSort without crashing.
define void @test13() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
define void @test14() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
entry:
%e = alloca %class.MyClass, align 4
br label %for.cond
@ -935,7 +976,7 @@ try.cont: ; preds = %catch.start, %for.e
}
; Check if the unwind destination mismatch stats are correct
; NOSORT-STAT: 16 wasm-cfg-stackify - Number of EH pad unwind mismatches found
; NOSORT-STAT: 17 wasm-cfg-stackify - Number of EH pad unwind mismatches found
declare void @foo()
declare void @bar()