[WebAssembly] Implement prolog/epilog insertion and FrameIndex elimination

Summary:
Use the SP32 physical register as the base for FrameIndex
lowering. Update it and the __stack_pointer global var in the prolog and
epilog. Extend the mapping of virtual registers to wasm locals to
include the physical registers.

Rather than modify the target-independent PrologEpilogInserter (which
asserts that there are no virtual registers left) include a
slightly-modified copy for Wasm that does not have this assertion and
only clears the virtual registers if scavenging was needed (which of
course it isn't for wasm).

Differential Revision: http://reviews.llvm.org/D15344

llvm-svn: 255392

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp
index ab539e1c287..4ad6eed7385 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp
@@ -69,7 +69,9 @@ bool WebAssemblyPeephole::runOnMachineFunction(MachineFunction &MF) {
         // can use $discard instead.
         MachineOperand &MO = MI.getOperand(0);
         unsigned OldReg = MO.getReg();
-        if (OldReg == MI.getOperand(3).getReg()) {
+        // TODO: Handle SP/physregs
+        if (OldReg == MI.getOperand(3).getReg()
+            && TargetRegisterInfo::isVirtualRegister(MI.getOperand(3).getReg())) {
           Changed = true;
           unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
           MO.setReg(NewReg);