[WebAssembly] Don't use set_local instructions explicitly.

The current approach to using get_local and set_local is to use them
implicitly, as register uses and defs. Introduce new copy instructions
which are themselves no-ops except for the get_local and set_local
that they imply, so that we use get_local and set_local consistently.

llvm-svn: 253905

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
index 1fa79020a2e..5922f95f039 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
@@ -98,6 +98,14 @@ multiclass LOCAL<WebAssemblyRegClass vt> {
   // TODO: set_local returns its operand value
   def SET_LOCAL_#vt : I<(outs), (ins i32imm:$regno, vt:$src), [],
                         "set_local\t$regno, $src">;
+
+  // COPY_LOCAL is not an actual instruction in wasm, but since we allow
+  // get_local and set_local to be implicit, we can have a COPY_LOCAL which
+  // is actually a no-op because all the work is done in the implied
+  // get_local and set_local.
+  let isAsCheapAsAMove = 1 in
+  def COPY_LOCAL_#vt : I<(outs vt:$res), (ins vt:$src), [],
+                         "copy_local\t$res, $src">;
 }
 defm : LOCAL<I32>;
 defm : LOCAL<I64>;