[DirectX] Eliminate resource global variables from module

llvm/include/llvm/IR/IntrinsicsDirectX.td

@@ -28,12 +28,14 @@ def int_dx_handle_fromBinding
           [IntrNoMem]>;
 
 def int_dx_typedBufferLoad
-    : DefaultAttrsIntrinsic<[llvm_any_ty], [llvm_any_ty, llvm_i32_ty]>;
+    : DefaultAttrsIntrinsic<[llvm_any_ty], [llvm_any_ty, llvm_i32_ty],
+                            [IntrReadMem]>;
 def int_dx_typedBufferLoad_checkbit
     : DefaultAttrsIntrinsic<[llvm_any_ty, llvm_i1_ty],
-                            [llvm_any_ty, llvm_i32_ty]>;
+                            [llvm_any_ty, llvm_i32_ty], [IntrReadMem]>;
 def int_dx_typedBufferStore
-    : DefaultAttrsIntrinsic<[], [llvm_any_ty, llvm_i32_ty, llvm_anyvector_ty]>;
+    : DefaultAttrsIntrinsic<[], [llvm_any_ty, llvm_i32_ty, llvm_anyvector_ty],
+                            [IntrWriteMem]>;
 
 // Cast between target extension handle types and dxil-style opaque handles
 def int_dx_cast_handle : Intrinsic<[llvm_any_ty], [llvm_any_ty]>;

llvm/lib/Target/DirectX/DXILOpLowering.cpp

@@ -204,6 +204,25 @@ class OpLowerer {
     CleanupCasts.clear();
   }
 
+  // Remove the resource global associated with the handleFromBinding call
+  // instruction and their uses as they aren't needed anymore.
+  // TODO: We should verify that all the globals get removed.
+  // It's expected we'll need a custom pass in the future that will eliminate
+  // the need for this here.
+  void removeResourceGlobals(CallInst *CI) {
+    for (User *User : make_early_inc_range(CI->users())) {
+      if (StoreInst *Store = dyn_cast<StoreInst>(User)) {
+        Value *V = Store->getOperand(1);
+        Store->eraseFromParent();
+        if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
+          if (GV->use_empty()) {
+            GV->removeDeadConstantUsers();
+            GV->eraseFromParent();
+          }
+      }
+    }
+  }
+
   [[nodiscard]] bool lowerToCreateHandle(Function &F) {
     IRBuilder<> &IRB = OpBuilder.getIRB();
     Type *Int8Ty = IRB.getInt8Ty();
@@ -228,6 +247,8 @@ class OpLowerer {
 
       Value *Cast = createTmpHandleCast(*OpCall, CI->getType());
 
+      removeResourceGlobals(CI);
+
       CI->replaceAllUsesWith(Cast);
       CI->eraseFromParent();
       return Error::success();
@@ -272,6 +293,8 @@ class OpLowerer {
 
       Value *Cast = createTmpHandleCast(*OpAnnotate, CI->getType());
 
+      removeResourceGlobals(CI);
+
       CI->replaceAllUsesWith(Cast);
       CI->eraseFromParent();
 

llvm/test/CodeGen/DirectX/ResourceGlobalElimination.ll

@@ -0,0 +1,44 @@
+; RUN: opt -S -passes='early-cse<memssa>' %s -o %t
+; RUN: FileCheck --check-prefixes=CSE,CHECK %s < %t
+; Finish compiling to verify that dxil-op-lower removes the globals entirely.
+; RUN: opt -mtriple=dxil-pc-shadermodel6.0-compute -S -dxil-op-lower %t -o - | FileCheck --check-prefixes=DXOP,CHECK %s
+; RUN: opt -mtriple=dxil-pc-shadermodel6.6-compute -S -dxil-op-lower %t -o - | FileCheck --check-prefixes=DXOP,CHECK %s
+; RUN: llc -mtriple=dxil-pc-shadermodel6.0-compute --filetype=asm -o - %t | FileCheck --check-prefixes=DXOP,CHECK %s
+; RUN: llc -mtriple=dxil-pc-shadermodel6.6-compute --filetype=asm -o - %t | FileCheck --check-prefixes=DXOP,CHECK %s
+
+; Ensure that EarlyCSE is able to eliminate unneeded loads of resource globals across typedBufferLoad.
+; Also that DXILOpLowering eliminates the globals entirely.
+
+%"class.hlsl::RWBuffer" = type { target("dx.TypedBuffer", <4 x float>, 1, 0, 0) }
+
+; DXOP-NOT: @In = global
+; DXOP-NOT: @Out = global
+@In = global %"class.hlsl::RWBuffer" zeroinitializer, align 4
+@Out = global %"class.hlsl::RWBuffer" zeroinitializer, align 4
+
+; CHECK-LABEL define void @main()
+define void @main() local_unnamed_addr #0 {
+entry:
+  ; DXOP: %In_h.i1 = call %dx.types.Handle @dx.op.createHandle
+  ; DXOP: %Out_h.i2 = call %dx.types.Handle @dx.op.createHandle
+  %In_h.i = call target("dx.TypedBuffer", <4 x float>, 1, 0, 0) @llvm.dx.handle.fromBinding.tdx.TypedBuffer_v4f32_1_0_0t(i32 0, i32 0, i32 1, i32 0, i1 false)
+  store target("dx.TypedBuffer", <4 x float>, 1, 0, 0) %In_h.i, ptr @In, align 4
+  %Out_h.i = call target("dx.TypedBuffer", <4 x float>, 1, 0, 0) @llvm.dx.handle.fromBinding.tdx.TypedBuffer_v4f32_1_0_0t(i32 4, i32 1, i32 1, i32 0, i1 false)
+  store target("dx.TypedBuffer", <4 x float>, 1, 0, 0) %Out_h.i, ptr @Out, align 4
+  ; CSE: call i32 @llvm.dx.flattened.thread.id.in.group()
+  %0 = call i32 @llvm.dx.flattened.thread.id.in.group()
+  ; CHECK-NOT: load {{.*}} ptr @In
+  %1 = load target("dx.TypedBuffer", <4 x float>, 1, 0, 0), ptr @In, align 4
+  ; CSE: call noundef <4 x float> @llvm.dx.typedBufferLoad.v4f32.tdx.TypedBuffer_v4f32_1_0_0t
+  %2 = call noundef <4 x float> @llvm.dx.typedBufferLoad.v4f32.tdx.TypedBuffer_v4f32_1_0_0t(target("dx.TypedBuffer", <4 x float>, 1, 0, 0) %1, i32 %0)
+  ; CHECK-NOT: load {{.*}} ptr @In
+  %3 = load target("dx.TypedBuffer", <4 x float>, 1, 0, 0), ptr @In, align 4
+  %4 = call noundef <4 x float> @llvm.dx.typedBufferLoad.v4f32.tdx.TypedBuffer_v4f32_1_0_0t(target("dx.TypedBuffer", <4 x float>, 1, 0, 0) %3, i32 %0)
+  %add.i = fadd <4 x float> %2, %4
+  call void @llvm.dx.typedBufferStore.tdx.TypedBuffer_v4f32_1_0_0t.v4f32(target("dx.TypedBuffer", <4 x float>, 1, 0, 0) %Out_h.i, i32 %0, <4 x float> %add.i)
+  ; CHECK: ret void
+  ret void
+}
+
+attributes #0 = { convergent noinline norecurse "frame-pointer"="all" "hlsl.numthreads"="8,1,1" "hlsl.shader"="compute" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+