[WebAssembly][CodeGen] IR support for WebAssembly local variables

This patch adds TargetStackID::WasmLocal.  This stack holds locations of
values that are only addressable by name -- not via a pointer to memory.
For the WebAssembly target, these objects are lowered to WebAssembly
local variables, which are managed by the WebAssembly run-time and are
not addressable by linear memory.

For the WebAssembly target IR indicates that an AllocaInst should be put
on TargetStackID::WasmLocal by putting it in the non-integral address
space WASM_ADDRESS_SPACE_WASM_VAR, with value 1.  SROA will mostly lift
these allocations to SSA locals, but any alloca that reaches instruction
selection (usually in non-optimized builds) will be assigned the new
TargetStackID there.  Loads and stores to those values are transformed
to new WebAssemblyISD::LOCAL_GET / WebAssemblyISD::LOCAL_SET nodes,
which then lower to the type-specific LOCAL_GET_I32 etc instructions via
tablegen patterns.

Differential Revision: https://reviews.llvm.org/D101140

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
index 7ed224d..4a0738d 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -239,8 +239,10 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
     Changed = true;
   }
 
-  // Start assigning local numbers after the last parameter.
+  // Start assigning local numbers after the last parameter and after any
+  // already-assigned locals.
   unsigned CurLocal = static_cast<unsigned>(MFI.getParams().size());
+  CurLocal += static_cast<unsigned>(MFI.getLocals().size());
 
   // Precompute the set of registers that are unused, so that we can insert
   // drops to their defs.