[DirectX] Eliminate resource global variables from module

By giving these intrinsics their appropriate attributes, loads of globals that are stored on the other side of these calls can be eliminated by the EarlyCSE pass.  Stores to the same globals and the globals themselves require more direct intervention as part of the handleFromBinding lowering.

Adds a test that verifies that the unneeded globals and their uses can be eliminated and also that the attributes are set properly.

Fixes #104271

Author: Greg Roth

llvm/lib/Target/DirectX/DXILOpLowering.cpp

@@ -204,6 +204,22 @@ class OpLowerer {
     CleanupCasts.clear();
   }
 
+  // Remove the resource global associated with the handleFromBinding call instruction
+  // and their uses as they aren't needed anymore.
+  void removeResourceGlobals(CallInst *CI) {
+    for (User *User : make_early_inc_range(CI->users())) {
+      if(StoreInst *Store = dyn_cast<StoreInst>(User)) {
+	if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Store->getOperand(1))) {
+	  Store->eraseFromParent();
+	  assert(GV->use_empty() && "Buffer global still has users");
+	  GV->removeDeadConstantUsers();
+	  GV->eraseFromParent();
+	}
+      }
+    }
+  }
+
+
   [[nodiscard]] bool lowerToCreateHandle(Function &F) {
     IRBuilder<> &IRB = OpBuilder.getIRB();
     Type *Int8Ty = IRB.getInt8Ty();
@@ -228,6 +244,8 @@ class OpLowerer {
 
       Value *Cast = createTmpHandleCast(*OpCall, CI->getType());
 
+      removeResourceGlobals(CI);
+
       CI->replaceAllUsesWith(Cast);
       CI->eraseFromParent();
       return Error::success();
@@ -272,6 +290,8 @@ class OpLowerer {
 
       Value *Cast = createTmpHandleCast(*OpAnnotate, CI->getType());
 
+      removeResourceGlobals(CI);
+
       CI->replaceAllUsesWith(Cast);
       CI->eraseFromParent();
 

llvm/test/CodeGen/DirectX/ResourceGlobalElimination.ll

@@ -1,55 +1,63 @@
-; RUN: opt -S -passes='early-cse<memssa>' %s | FileCheck %s
+; 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: llc -mtriple=dxil-pc-shadermodel6.0-compute  --filetype=asm -o - %t | FileCheck --check-prefixes=LLC,CHECK %s
+; RUN: llc -mtriple=dxil-pc-shadermodel6.6-compute  --filetype=asm -o - %t | FileCheck --check-prefixes=LLC,CHECK %s
 
 ; Ensure that EarlyCSE is able to eliminate unneeded loads of resource globals across typedBufferLoad.
+; Also that DXILOpLowering eliminates the globals entirely.
 
 target datalayout = "e-m:e-p:32:32-i1:32-i8:8-i16:16-i32:32-i64:64-f16:16-f32:32-f64:64-n8:16:32:64"
 target triple = "dxilv1.6-unknown-shadermodel6.6-compute"
 
 %"class.hlsl::RWBuffer" = type { target("dx.TypedBuffer", <4 x float>, 1, 0, 0) }
 
+; LLC-NOT: @In = global
+; LLC-NOT: @Out = global
 @In = global %"class.hlsl::RWBuffer" zeroinitializer, align 4
 @Out = global %"class.hlsl::RWBuffer" zeroinitializer, align 4
 
 ; Function Attrs: convergent noinline norecurse
 ; CHECK-LABEL define void @main()
 define void @main() local_unnamed_addr #0 {
 entry:
-  %tmp = alloca target("dx.TypedBuffer", <4 x float>, 1, 0, 0), align 4
+  ; LLC: %In_h.i1 = call %dx.types.Handle @dx.op.createHandle
+  ; LLC: %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
-  ; CHECK: call i32 @llvm.dx.flattened.thread.id.in.group()
+  ; 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
-  ; CHECK call noundef <4 x float> @llvm.dx.typedBufferLoad.v4f32.tdx.TypedBuffer_v4f32_1_0_0t
+  ; 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
-  store target("dx.TypedBuffer", <4 x float>, 1, 0, 0) %Out_h.i, ptr %tmp, align 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
 }
 
 ; Function Attrs: mustprogress nofree nosync nounwind willreturn memory(none)
 declare i32 @llvm.dx.flattened.thread.id.in.group() #1
 
 ; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn
-; CHECK: declare <4 x float> @llvm.dx.typedBufferLoad.v4f32.tdx.TypedBuffer_v4f32_1_0_0t(target("dx.TypedBuffer", <4 x float>, 1, 0, 0), i32) [[ROAttr:#[0-9]+]]
+; CSE: declare <4 x float> @llvm.dx.typedBufferLoad.v4f32.tdx.TypedBuffer_v4f32_1_0_0t(target("dx.TypedBuffer", <4 x float>, 1, 0, 0), i32) [[ROAttr:#[0-9]+]]
 declare <4 x float> @llvm.dx.typedBufferLoad.v4f32.tdx.TypedBuffer_v4f32_1_0_0t(target("dx.TypedBuffer", <4 x float>, 1, 0, 0), i32) #2
 
 ; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn
-; CHECK: declare void @llvm.dx.typedBufferStore.tdx.TypedBuffer_v4f32_1_0_0t.v4f32(target("dx.TypedBuffer", <4 x float>, 1, 0, 0), i32, <4 x float>) [[WOAttr:#[0-9]+]]
+; CSE: declare void @llvm.dx.typedBufferStore.tdx.TypedBuffer_v4f32_1_0_0t.v4f32(target("dx.TypedBuffer", <4 x float>, 1, 0, 0), i32, <4 x float>) [[WOAttr:#[0-9]+]]
 declare void @llvm.dx.typedBufferStore.tdx.TypedBuffer_v4f32_1_0_0t.v4f32(target("dx.TypedBuffer", <4 x float>, 1, 0, 0), i32, <4 x float>) #2
 
 ; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(none)
 declare target("dx.TypedBuffer", <4 x float>, 1, 0, 0) @llvm.dx.handle.fromBinding.tdx.TypedBuffer_v4f32_1_0_0t(i32, i32, i32, i32, i1) #3
 
-; CHECK: attributes [[ROAttr]] = { {{.*}} memory(read) }
-; CHECK: attributes [[WOAttr]] = { {{.*}} memory(write) }
+; CSE: attributes [[ROAttr]] = { {{.*}} memory(read) }
+; CSE: attributes [[WOAttr]] = { {{.*}} memory(write) }
 
 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" }
 attributes #1 = { mustprogress nofree nosync nounwind willreturn memory(none) }