[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
llvm-svn: 357015
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp
index a7c1209..3f5aba0 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp
@@ -101,6 +101,13 @@
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 @@
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 @@
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 @@
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();