[WEbAssembly] Clear frame base vreg in explicit-locals when stack pointer is dead

Having an alloca in a function causes the stack pointer to be generated in the
prolog, but if it's unused other than for debug info, explicit-locals will drop
it and not allocate a local. In this case we need to reset the FrameBaseVreg.

Differential Revision: https://reviews.llvm.org/D76784

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
index 56da3ec..03b70f3 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -313,6 +313,8 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
                     .addReg(NewReg);
             // After the drop instruction, this reg operand will not be used
             Drop->getOperand(0).setIsKill();
+            if (MFI.isFrameBaseVirtual() && OldReg == MFI.getFrameBaseVreg())
+              MFI.clearFrameBaseVreg();
           } else {
             unsigned LocalId = getLocalId(Reg2Local, MFI, CurLocal, OldReg);
             unsigned Opc = getLocalSetOpcode(RC);