[DirectX] Allow llvm.assume intrinsic to pass on to DXIL

[farzonl]

fixes #165051

Change is just to let the assume intrinsic pass on unmodified. Test is to confirm the DXIL disassembler doesn't blow up whe we generate DXIL with this intrinsic.

[llvmbot]

@llvm/pr-subscribers-backend-directx

Author: Farzon Lotfi (farzonl)

Changes

fixes #165051

Change is just to let the assume intrinsic pass on unmodified. Test is to confirm the DXIL disassembler doesn't blow up whe we generate DXIL with this intrinsic.

---

Full diff: https://github.com/llvm/llvm-project/pull/165311.diff

2 Files Affected:

• (modified) llvm/lib/Target/DirectX/DXILOpLowering.cpp (+2)
• (added) llvm/test/tools/dxil-dis/llvm_assume.ll (+11)

diff --git a/llvm/lib/Target/DirectX/DXILOpLowering.cpp b/llvm/lib/Target/DirectX/DXILOpLowering.cpp
index e46a393e50906..8720460cceb20 100644
--- a/llvm/lib/Target/DirectX/DXILOpLowering.cpp
+++ b/llvm/lib/Target/DirectX/DXILOpLowering.cpp
@@ -904,6 +904,8 @@ class OpLowerer {
       case Intrinsic::dx_resource_casthandle:
       // NOTE: llvm.dbg.value is supported as is in DXIL.
       case Intrinsic::dbg_value:
+      // NOTE: llvm.assume is supported as is in DXIL.
+      case Intrinsic::assume:
       case Intrinsic::not_intrinsic:
         if (F.use_empty())
           F.eraseFromParent();
diff --git a/llvm/test/tools/dxil-dis/llvm_assume.ll b/llvm/test/tools/dxil-dis/llvm_assume.ll
new file mode 100644
index 0000000000000..f5be66c0d192f
--- /dev/null
+++ b/llvm/test/tools/dxil-dis/llvm_assume.ll
@@ -0,0 +1,11 @@
+; RUN: llc --filetype=obj %s -o - | dxil-dis -o - | FileCheck %s
+
+target triple = "dxil-pc-shadermodel6.7-library"
+
+define void @test_llvm_assume(i1 %0)  {
+; CHECK-LABEL: test_llvm_assume
+; CHECK-NEXT: tail call void @llvm.assume(i1 %0)
+tail call void @llvm.assume(i1 %0)
+ret void
+}
+

[farzonl]

Just a note, we will want to use the offload test suite to see if the AMD, Intel, Nvidia, and Qualcomm gpu drivers can handle the assume llvm intrinsic. If they can't we should just remove this intrinsic. But for now we will allow it to pass on so we can run experiments. I can confirm right now that the metal tests are working with llvm.assume.