[llvm] r357015 - [WebAssembly] Don't analyze branches after CFGStackify
Heejin Ahn via llvm-commits
llvm-commits at lists.llvm.org
Tue Mar 26 11:21:20 PDT 2019
Author: aheejin
Date: Tue Mar 26 11:21:20 2019
New Revision: 357015
URL: http://llvm.org/viewvc/llvm-project?rev=357015&view=rev
Log:
[WebAssembly] Don't analyze branches after CFGStackify
Summary:
`WebAssembly::analyzeBranch` now does not analyze anything if the
function is CFG stackified. We were previously doing similar things by
checking if a branch's operand is whether an integer or an MBB, but this
failed to bail out when a BB did not have any terminators.
Consider this case:
```
bb0:
try $label0
call @foo // unwinds to %ehpad
bb1:
...
br $label0 // jumps to %cont. can be deleted
ehpad:
catch
...
cont:
end_try
```
Here `br $label0` will be deleted in CFGStackify's
`removeUnnecessaryInstrs` function, because we jump to the %cont block
even without the branch. But in this case, MachineVerifier fails to
verify this, because `ehpad` is not a successor of `bb1` even if `bb1`
does not have any terminators. MachineVerifier incorrectly thinks `bb1`
falls through to the next block.
This pass now consistently rejects all analysis after CFGStackify
whether a BB has terminators or not, also making the MachineVerifier
work. (MachineVerifier does not try to verify relationships between BBs
if `analyzeBranch` fails, the behavior we want after CFGStackify.)
This also adds a new option `-wasm-disable-ehpad-sort` for testing. This
option helps create the sorted order we want to test, and without the
fix in this patch, the tests in cfg-stackify-eh.ll fail at
MachineVerifier with `-wasm-disable-ehpad-sort`.
Reviewers: dschuff
Subscribers: sunfish, sbc100, jgravelle-google, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59740
Modified:
llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp
llvm/trunk/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp
llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp?rev=357015&r1=357014&r2=357015&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp Tue Mar 26 11:21:20 2019
@@ -34,6 +34,14 @@ using namespace llvm;
#define DEBUG_TYPE "wasm-cfg-sort"
+// Option to disable EH pad first sorting. Only for testing unwind destination
+// mismatches in CFGStackify.
+static cl::opt<bool> WasmDisableEHPadSort(
+ "wasm-disable-ehpad-sort", cl::ReallyHidden,
+ cl::desc(
+ "WebAssembly: Disable EH pad-first sort order. Testing purpose only."),
+ cl::init(false));
+
namespace {
// Wrapper for loops and exceptions
@@ -187,10 +195,12 @@ namespace {
struct CompareBlockNumbers {
bool operator()(const MachineBasicBlock *A,
const MachineBasicBlock *B) const {
- if (A->isEHPad() && !B->isEHPad())
- return false;
- if (!A->isEHPad() && B->isEHPad())
- return true;
+ if (!WasmDisableEHPadSort) {
+ if (A->isEHPad() && !B->isEHPad())
+ return false;
+ if (!A->isEHPad() && B->isEHPad())
+ return true;
+ }
return A->getNumber() > B->getNumber();
}
@@ -199,11 +209,12 @@ struct CompareBlockNumbers {
struct CompareBlockNumbersBackwards {
bool operator()(const MachineBasicBlock *A,
const MachineBasicBlock *B) const {
- // We give a higher priority to an EH pad
- if (A->isEHPad() && !B->isEHPad())
- return false;
- if (!A->isEHPad() && B->isEHPad())
- return true;
+ if (!WasmDisableEHPadSort) {
+ if (A->isEHPad() && !B->isEHPad())
+ return false;
+ if (!A->isEHPad() && B->isEHPad())
+ return true;
+ }
return A->getNumber() < B->getNumber();
}
Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp?rev=357015&r1=357014&r2=357015&view=diff
==============================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp Tue Mar 26 11:21:20 2019
@@ -101,6 +101,13 @@ bool WebAssemblyInstrInfo::analyzeBranch
MachineBasicBlock *&FBB,
SmallVectorImpl<MachineOperand> &Cond,
bool /*AllowModify*/) const {
+ const auto &MFI = *MBB.getParent()->getInfo<WebAssemblyFunctionInfo>();
+ // WebAssembly has control flow that doesn't have explicit branches or direct
+ // fallthrough (e.g. try/catch), which can't be modeled by analyzeBranch. It
+ // is created after CFGStackify.
+ if (MFI.isCFGStackified())
+ return true;
+
bool HaveCond = false;
for (MachineInstr &MI : MBB.terminators()) {
switch (MI.getOpcode()) {
@@ -110,9 +117,6 @@ bool WebAssemblyInstrInfo::analyzeBranch
case WebAssembly::BR_IF:
if (HaveCond)
return true;
- // If we're running after CFGStackify, we can't optimize further.
- if (!MI.getOperand(0).isMBB())
- return true;
Cond.push_back(MachineOperand::CreateImm(true));
Cond.push_back(MI.getOperand(1));
TBB = MI.getOperand(0).getMBB();
@@ -121,18 +125,12 @@ bool WebAssemblyInstrInfo::analyzeBranch
case WebAssembly::BR_UNLESS:
if (HaveCond)
return true;
- // If we're running after CFGStackify, we can't optimize further.
- if (!MI.getOperand(0).isMBB())
- return true;
Cond.push_back(MachineOperand::CreateImm(false));
Cond.push_back(MI.getOperand(1));
TBB = MI.getOperand(0).getMBB();
HaveCond = true;
break;
case WebAssembly::BR:
- // If we're running after CFGStackify, we can't optimize further.
- if (!MI.getOperand(0).isMBB())
- return true;
if (!HaveCond)
TBB = MI.getOperand(0).getMBB();
else
@@ -141,9 +139,6 @@ bool WebAssemblyInstrInfo::analyzeBranch
case WebAssembly::BR_ON_EXN:
if (HaveCond)
return true;
- // If we're running after CFGStackify, we can't optimize further.
- if (!MI.getOperand(0).isMBB())
- return true;
Cond.push_back(MachineOperand::CreateImm(true));
Cond.push_back(MI.getOperand(2));
TBB = MI.getOperand(0).getMBB();
Modified: llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify-eh.ll?rev=357015&r1=357014&r2=357015&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify-eh.ll (original)
+++ llvm/trunk/test/CodeGen/WebAssembly/cfg-stackify-eh.ll Tue Mar 26 11:21:20 2019
@@ -1,5 +1,6 @@
; 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 | FileCheck %s
; 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
target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
target triple = "wasm32-unknown-unknown"
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