[WebAssembly] Unstackify regs after fixing unwinding mismatches
Summary:
Fixing unwind mismatches for exception handling can result in splicing
existing BBs and moving some of instructions to new BBs. In this case
some of stackified def registers in the original BB can be used in the
split BB. For example, we have this BB and suppose %r0 is a stackified
register.
```
bb.1:
%r0 = call @foo
... use %r0 ...
```
After fixing unwind mismatches in CFGStackify, `bb.1` can be split and
some instructions can be moved to a newly created BB:
```
bb.1:
%r0 = call @foo
bb.split (new):
... use %r0 ...
```
In this case we should make %r0 un-stackified, because its use is now in
another BB.
When spliting a BB, this CL unstackifies all def registers that have
uses in the new split BB.
Reviewers: dschuff
Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D68218
llvm-svn: 373301
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
index 6c38dea..6b20946 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -694,8 +694,26 @@
}
}
+// 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) {
+ for (auto &MI : Split) {
+ for (auto &MO : MI.explicit_uses()) {
+ if (!MO.isReg() || Register::isPhysicalRegister(MO.getReg()))
+ continue;
+ if (MachineInstr *Def = MRI.getUniqueVRegDef(MO.getReg()))
+ if (Def->getParent() == &MBB)
+ MFI.unstackifyVReg(MO.getReg());
+ }
+ }
+}
+
bool WebAssemblyCFGStackify::fixUnwindMismatches(MachineFunction &MF) {
const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+ auto &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
MachineRegisterInfo &MRI = MF.getRegInfo();
// Linearizing the control flow by placing TRY / END_TRY markers can create
@@ -1007,6 +1025,7 @@
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);
// Fix predecessor-successor relationship.
BrDest->transferSuccessors(EHPad);
EHPad->addSuccessor(BrDest);
@@ -1122,6 +1141,7 @@
// new nested continuation BB.
NestedCont->splice(NestedCont->end(), MBB,
std::next(RangeEnd->getIterator()), MBB->end());
+ unstackifyVRegsUsedInSplitBB(*MBB, *NestedCont, MFI, MRI);
registerTryScope(NestedTry, NestedEndTry, NestedEHPad);
// Fix predecessor-successor relationship.