[WebAssembly] Implement ReverseBranchCondition, and re-enable MachineBlockPlacement
This patch introduces a codegen-only instruction currently named br_unless,
which makes it convenient to implement ReverseBranchCondition and re-enable
the MachineBlockPlacement pass. Then in a late pass, it lowers br_unless
back into br_if.
Differential Revision: http://reviews.llvm.org/D14995
llvm-svn: 254826
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
index 29fb89c..b546992 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -171,10 +171,6 @@
// Fails with: should be run after register allocation.
disablePass(&MachineCopyPropagationID);
- // TODO: Until we get ReverseBranchCondition support, MachineBlockPlacement
- // can create ugly-looking control flow.
- disablePass(&MachineBlockPlacementID);
-
// Run the register coloring pass to reduce the total number of registers.
addPass(createWebAssemblyRegColoring());
}
@@ -183,6 +179,9 @@
// Put the CFG in structured form; insert BLOCK and LOOP markers.
addPass(createWebAssemblyCFGStackify());
+ // Lower br_unless into br_if.
+ addPass(createWebAssemblyLowerBrUnless());
+
// Create a mapping from LLVM CodeGen virtual registers to wasm registers.
addPass(createWebAssemblyRegNumbering());