[WebAssembly] Convert stackified IMPLICIT_DEF into constant 0.
Since IMPLIFIT_DEF instructions are omitted in the output, when the output
of an IMPLICIT_DEF instruction is stackified, the resulting register lacks
an explicit push, leading to a push/pop mismatch. Fix this by converting
such IMPLICIT_DEFs into CONST_I32 0 instructions so that they have explicit
pushes.
llvm-svn: 286274
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
index 894f2dc..32ee09e 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
@@ -87,6 +87,37 @@
/*isImp=*/true));
}
+// Convert an IMPLICIT_DEF instruction into an instruction which defines
+// a constant zero value.
+static void ConvertImplicitDefToConstZero(MachineInstr *MI,
+ MachineRegisterInfo &MRI,
+ const TargetInstrInfo *TII,
+ MachineFunction &MF) {
+ assert(MI->getOpcode() == TargetOpcode::IMPLICIT_DEF);
+
+ const auto *RegClass =
+ MRI.getRegClass(MI->getOperand(0).getReg());
+ if (RegClass == &WebAssembly::I32RegClass) {
+ MI->setDesc(TII->get(WebAssembly::CONST_I32));
+ MI->addOperand(MachineOperand::CreateImm(0));
+ } else if (RegClass == &WebAssembly::I64RegClass) {
+ MI->setDesc(TII->get(WebAssembly::CONST_I64));
+ MI->addOperand(MachineOperand::CreateImm(0));
+ } else if (RegClass == &WebAssembly::F32RegClass) {
+ MI->setDesc(TII->get(WebAssembly::CONST_F32));
+ ConstantFP *Val = cast<ConstantFP>(Constant::getNullValue(
+ Type::getFloatTy(MF.getFunction()->getContext())));
+ MI->addOperand(MachineOperand::CreateFPImm(Val));
+ } else if (RegClass == &WebAssembly::F64RegClass) {
+ MI->setDesc(TII->get(WebAssembly::CONST_F64));
+ ConstantFP *Val = cast<ConstantFP>(Constant::getNullValue(
+ Type::getDoubleTy(MF.getFunction()->getContext())));
+ MI->addOperand(MachineOperand::CreateFPImm(Val));
+ } else {
+ llvm_unreachable("Unexpected reg class");
+ }
+}
+
// Determine whether a call to the callee referenced by
// MI->getOperand(CalleeOpNo) reads memory, writes memory, and/or has side
// effects.
@@ -791,6 +822,12 @@
continue;
}
+ // If the instruction we just stackified is an IMPLICIT_DEF, convert it
+ // to a constant 0 so that the def is explicit, and the push/pop
+ // correspondence is maintained.
+ if (Insert->getOpcode() == TargetOpcode::IMPLICIT_DEF)
+ ConvertImplicitDefToConstZero(Insert, MRI, TII, MF);
+
// We stackified an operand. Add the defining instruction's operands to
// the worklist stack now to continue to build an ever deeper tree.
Commuting.Reset();