[WebAssembly] Optimize away return instructions using fallthroughs.
This saves a small amount of code size, and is a first small step toward
passing values on the stack across block boundaries.
Differential Review: http://reviews.llvm.org/D20450
llvm-svn: 270294
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
index ba4e1f9..444e275 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
@@ -71,6 +71,10 @@
multiclass RETURN<WebAssemblyRegClass vt> {
def RETURN_#vt : I<(outs), (ins vt:$val), [(WebAssemblyreturn vt:$val)],
"return \t$val">;
+ // Equivalent to RETURN_#vt, for use at the end of a function when wasm
+ // semantics return by falling off the end of the block.
+ let isCodeGenOnly = 1 in
+ def FALLTHROUGH_RETURN_#vt : I<(outs), (ins vt:$val), []>;
}
let isTerminator = 1, hasCtrlDep = 1, isBarrier = 1 in {
@@ -80,6 +84,10 @@
defm : RETURN<F32>;
defm : RETURN<F64>;
def RETURN_VOID : I<(outs), (ins), [(WebAssemblyreturn)], "return">;
+
+ // This is to RETURN_VOID what FALLTHROUGH_RETURN_#vt is to RETURN_#vt.
+ let isCodeGenOnly = 1 in
+ def FALLTHROUGH_RETURN_VOID : I<(outs), (ins), []>;
} // isReturn = 1
def UNREACHABLE : I<(outs), (ins), [(trap)], "unreachable">;
} // isTerminator = 1, hasCtrlDep = 1, isBarrier = 1
