[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

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp
index e149d9cce71..11f44775b5e 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyPeephole.cpp
@@ -64,7 +64,7 @@ bool WebAssemblyPeephole::runOnMachineFunction(MachineFunction &MF) {
         // can use $discard instead.
         MachineOperand &MO = MI.getOperand(0);
         unsigned OldReg = MO.getReg();
-        if (OldReg == MI.getOperand(2).getReg()) {
+        if (OldReg == MI.getOperand(3).getReg()) {
           unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
           MO.setReg(NewReg);
           MO.setIsDead();