AMDGPU: Add new intrinsic llvm.amdgcn.kill(i1)

Summary:
Kill the thread if operand 0 == false.
llvm.amdgcn.wqm.vote can be applied to the operand.

Also allow kill in all shader stages.

Reviewers: arsenm, nhaehnle

Subscribers: kzhuravl, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D38544

llvm-svn: 316427

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index b2282cfd419..3a5debc3223 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3539,6 +3539,14 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
 
     return replaceInstUsesWith(*II, II->getArgOperand(0));
   }
+  case Intrinsic::amdgcn_kill: {
+    const ConstantInt *C = dyn_cast<ConstantInt>(II->getArgOperand(0));
+    if (!C || !C->getZExtValue())
+      break;
+
+    // amdgcn.kill(i1 1) is a no-op
+    return eraseInstFromFunction(CI);
+  }
   case Intrinsic::stackrestore: {
     // If the save is right next to the restore, remove the restore.  This can
     // happen when variable allocas are DCE'd.