[llvm] [DirectX] Remove llvm.assume intrinsic (PR #166697)

[Farzon Lotfi via llvm-commits]

https://github.com/farzonl created https://github.com/llvm/llvm-project/pull/166697

fixes #165051

This change reverts the experiment we did for #165311

While some backends seem to support llvm.assume without validation The validator itself does not so it makes more sense to just remove it.

>From c5d3d134c85e173d8ee068eb56e17b24deb9078b Mon Sep 17 00:00:00 2001
From: Farzon Lotfi <farzonlotfi at microsoft.com>
Date: Wed, 5 Nov 2025 23:35:08 -0500
Subject: [PATCH] [DirectX] Remove llvm.assume intrinsic

fixes #165051

This change reverts the experiment we did for #165311

While some backends seem to support llvm.assume without validation
The validator itself does not so it makes more sense to just remove it.
---
 llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp |  4 ++++
 llvm/lib/Target/DirectX/DXILOpLowering.cpp         |  2 --
 llvm/test/CodeGen/DirectX/llvm_assume.ll           |  9 +++++++++
 llvm/test/tools/dxil-dis/llvm_assume.ll            | 11 -----------
 4 files changed, 13 insertions(+), 13 deletions(-)
 create mode 100644 llvm/test/CodeGen/DirectX/llvm_assume.ll
 delete mode 100644 llvm/test/tools/dxil-dis/llvm_assume.ll

diff --git a/llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp b/llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp
index ebb7c2607c0c8..e0d2dbde92150 100644
--- a/llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp
+++ b/llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp
@@ -197,6 +197,7 @@ static Value *expand16BitIsNormal(CallInst *Orig) {
 
 static bool isIntrinsicExpansion(Function &F) {
   switch (F.getIntrinsicID()) {
+  case Intrinsic::assume:
   case Intrinsic::abs:
   case Intrinsic::atan2:
   case Intrinsic::exp:
@@ -988,6 +989,9 @@ static bool expandIntrinsic(Function &F, CallInst *Orig) {
   case Intrinsic::abs:
     Result = expandAbs(Orig);
     break;
+  case Intrinsic::assume:
+    Orig->eraseFromParent();
+    return true;
   case Intrinsic::atan2:
     Result = expandAtan2Intrinsic(Orig);
     break;
diff --git a/llvm/lib/Target/DirectX/DXILOpLowering.cpp b/llvm/lib/Target/DirectX/DXILOpLowering.cpp
index 8720460cceb20..e46a393e50906 100644
--- a/llvm/lib/Target/DirectX/DXILOpLowering.cpp
+++ b/llvm/lib/Target/DirectX/DXILOpLowering.cpp
@@ -904,8 +904,6 @@ 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/CodeGen/DirectX/llvm_assume.ll b/llvm/test/CodeGen/DirectX/llvm_assume.ll
new file mode 100644
index 0000000000000..d739592b75d78
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/llvm_assume.ll
@@ -0,0 +1,9 @@
+; RUN: opt -S -dxil-intrinsic-expansion -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
+
+define void @test_llvm_assume(i1 %0)  {
+; CHECK-LABEL: test_llvm_assume
+; CHECK-NEXT: ret void
+tail call void @llvm.assume(i1 %0)
+ret void
+}
+
diff --git a/llvm/test/tools/dxil-dis/llvm_assume.ll b/llvm/test/tools/dxil-dis/llvm_assume.ll
deleted file mode 100644
index f5be66c0d192f..0000000000000
--- a/llvm/test/tools/dxil-dis/llvm_assume.ll
+++ /dev/null
@@ -1,11 +0,0 @@
-; 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
-}
-