[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

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h b/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h
index 79950a6b257..c2f695db4a0 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h
@@ -86,6 +86,12 @@ class WebAssemblyFunctionInfo final : public MachineFunctionInfo {
     assert(VReg = WARegs.size());
     WARegs.push_back(WAReg);
   }
+
+  // For a given stackified WAReg, return the id number to print with push/pop.
+  static unsigned getWARegStackId(unsigned Reg) {
+    assert(Reg & INT32_MIN);
+    return Reg & INT32_MAX;
+  }
 };
 
 } // end namespace llvm