[WebAssembly] Check in an initial CFG Stackifier pass

This pass implements a simple algorithm for conversion from CFG to
wasm's structured control flow. It doesn't yet handle multiple-entry
loops; that will be added in a future patch.

It also adds initial support for switch statements.

Differential Revision: http://reviews.llvm.org/D12735

llvm-svn: 247818

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
index 5f53e4a00d4..a349da6b971 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
@@ -25,6 +25,29 @@
  * switch: switch statement with fallthrough
  */
 
+let isBranch = 1, isTerminator = 1, hasCtrlDep = 1 in {
+def BRIF : I<(outs), (ins bb_op:$dst, Int32:$a),
+             [(brcond Int32:$a, bb:$dst)]>;
+let isBarrier = 1 in {
+def BR   : I<(outs), (ins bb_op:$dst),
+             [(br bb:$dst)]>;
+} // isBarrier = 1
+} // isBranch = 1, isTerminator = 1, hasCtrlDep = 1
+
+// TODO: SelectionDAG's lowering insists on using a pointer as the index for
+// jump tables, so in practice we don't ever use SWITCH_I64 in wasm32 mode
+// currently.
+let isTerminator = 1, hasCtrlDep = 1, isBarrier = 1 in {
+def SWITCH_I32 : I<(outs), (ins Int32:$index, variable_ops),
+                   [(WebAssemblyswitch Int32:$index)]>;
+def SWITCH_I64 : I<(outs), (ins Int64:$index, variable_ops),
+                   [(WebAssemblyswitch Int64:$index)]>;
+} // isTerminator = 1, hasCtrlDep = 1, isBarrier = 1
+
+// Placemarkers to indicate the start of a block or loop scope.
+def BLOCK     : I<(outs), (ins bb_op:$dst), []>;
+def LOOP      : I<(outs), (ins bb_op:$dst), []>;
+
 multiclass RETURN<WebAssemblyRegClass vt> {
   def RETURN_#vt : I<(outs), (ins vt:$val), [(WebAssemblyreturn vt:$val)]>;
 }