[HLSL] Apply NoRecurse attrib to all HLSL functions (#105907)

Greg Roth · web-flow · commit 2dc3b5098795 · 2024-08-29T10:01:52.000-07:00
Previously, functions named "main" got the NoRecurse attribute consistent with the behavior of C++, which HLSL largely follows. However, standard recursion is not allowed in HLSL, so all functions should really have this attribute. This doesn't prevent recursion, but rather signals that these functions aren't expected to recurse. Practically, this was done so that entry point functions named "main" would have all have the same attributes as otherwise identical entry points with other names. This required small changes to the this assignment tests because they no longer generate so many attribute sets since more of them match. related to #105244 but done to simplify testing for #89806
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -1064,13 +1064,17 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
   // OpenCL C 2.0 v2.2-11 s6.9.i:
   //     Recursion is not supported.
   //
+  // HLSL
+  //     Recursion is not supported.
+  //
   // SYCL v1.2.1 s3.10:
   //     kernels cannot include RTTI information, exception classes,
   //     recursive code, virtual functions or make use of C++ libraries that
   //     are not compiled for the device.
-  if (FD && ((getLangOpts().CPlusPlus && FD->isMain()) ||
-             getLangOpts().OpenCL || getLangOpts().SYCLIsDevice ||
-             (getLangOpts().CUDA && FD->hasAttr<CUDAGlobalAttr>())))
+  if (FD &&
+      ((getLangOpts().CPlusPlus && FD->isMain()) || getLangOpts().OpenCL ||
+       getLangOpts().HLSL || getLangOpts().SYCLIsDevice ||
+       (getLangOpts().CUDA && FD->hasAttr<CUDAGlobalAttr>())))
     Fn->addFnAttr(llvm::Attribute::NoRecurse);
 
   llvm::RoundingMode RM = getLangOpts().getDefaultRoundingMode();
diff --git a/clang/test/CodeGenHLSL/implicit-norecurse-attrib.hlsl b/clang/test/CodeGenHLSL/implicit-norecurse-attrib.hlsl
@@ -0,0 +1,93 @@
+// RUN: %clang_cc1 -x hlsl -triple dxil-pc-shadermodel6.3-library  -finclude-default-header %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+// RUN: %clang_cc1 -x hlsl -triple dxil-pc-shadermodel6.0-compute  -finclude-default-header %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+
+// Verify that a few different function types all get the NoRecurse attribute
+
+#define MAX 100
+
+struct Node {
+  uint value;
+  uint key;
+  uint left, right;
+};
+
+// CHECK: Function Attrs:{{.*}}norecurse
+// CHECK: define noundef i32 @"?Find@@YAIY0GE@UNode@@I@Z"(ptr noundef byval([100 x %struct.Node]) align 4 %SortedTree, i32 noundef %key) [[IntAttr:\#[0-9]+]]
+// CHECK: ret i32
+// Find and return value corresponding to key in the SortedTree
+uint Find(Node SortedTree[MAX], uint key) {
+  uint nix = 0; // head
+  while(true) {
+    if (nix < 0)
+      return 0.0; // Not found
+    Node n = SortedTree[nix];
+    if (n.key == key)
+      return n.value;
+    if (key < n.key)
+      nix = n.left;
+    else
+      nix = n.right;
+  }
+}
+
+// CHECK: Function Attrs:{{.*}}norecurse
+// CHECK: define noundef i1 @"?InitTree@@YA_NY0GE@UNode@@V?$RWBuffer@T?$__vector@I$03@__clang@@@hlsl@@I@Z"(ptr noundef byval([100 x %struct.Node]) align 4 %tree, ptr noundef byval(%"class.hlsl::RWBuffer") align 4 %encodedTree, i32 noundef %maxDepth) [[ExtAttr:\#[0-9]+]]
+// CHECK: ret i1
+// Initialize tree with given buffer
+// Imagine the inout works
+export
+bool InitTree(/*inout*/ Node tree[MAX], RWBuffer<uint4> encodedTree, uint maxDepth) {
+  uint size = pow(2.f, maxDepth) - 1;
+  if (size > MAX) return false;
+  for (uint i = 1; i < size; i++) {
+    tree[i].value = encodedTree[i].x;
+    tree[i].key   = encodedTree[i].y;
+    tree[i].left  = encodedTree[i].z;
+    tree[i].right = encodedTree[i].w;
+  }
+  return true;
+}
+
+RWBuffer<uint4> gTree;
+
+// Mangled entry points are internal
+// CHECK: Function Attrs:{{.*}}norecurse
+// CHECK: define internal void @"?main@@YAXI@Z"(i32 noundef %GI) [[IntAttr]]
+// CHECK: ret void
+
+// Canonical entry points are external and shader attributed
+// CHECK: Function Attrs:{{.*}}norecurse
+// CHECK: define void @main() [[EntryAttr:\#[0-9]+]]
+// CHECK: ret void
+
+[numthreads(1,1,1)]
+[shader("compute")]
+void main(uint GI : SV_GroupIndex) {
+  Node haystack[MAX];
+  uint needle = 0;
+  if (InitTree(haystack, gTree, GI))
+    needle = Find(haystack, needle);
+}
+
+// Mangled entry points are internal
+// CHECK: Function Attrs:{{.*}}norecurse
+// CHECK: define internal void @"?defaultMain@@YAXXZ"() [[IntAttr]]
+// CHECK: ret void
+
+// Canonical entry points are external and shader attributed
+// CHECK: Function Attrs:{{.*}}norecurse
+// CHECK: define void @defaultMain() [[EntryAttr]]
+// CHECK: ret void
+
+[numthreads(1,1,1)]
+[shader("compute")]
+void defaultMain() {
+  Node haystack[MAX];
+  uint needle = 0;
+  if (InitTree(haystack, gTree, 4))
+    needle = Find(haystack, needle);
+}
+
+// CHECK: attributes [[IntAttr]] = {{.*}} norecurse
+// CHECK: attributes [[ExtAttr]] = {{.*}} norecurse
+// CHECK: attributes [[EntryAttr]] = {{.*}} norecurse
diff --git a/clang/test/CodeGenHLSL/this-assignment-overload.hlsl b/clang/test/CodeGenHLSL/this-assignment-overload.hlsl
@@ -25,7 +25,7 @@ void main() {
 }
 
 // This test makes a probably safe assumption that HLSL 202x includes operator overloading for assignment operators.
-// CHECK:     define linkonce_odr noundef i32 @"?getFirst@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #2 align 2 {
+// CHECK:     define linkonce_odr noundef i32 @"?getFirst@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #0 align 2 {
 // CHECK-NEXT:entry:
 // CHECK-NEXT:%this.addr = alloca ptr, align 4
 // CHECK-NEXT:%Another = alloca %struct.Pair, align 4
@@ -42,7 +42,7 @@ void main() {
 // CHECK-NEXT:%0 = load i32, ptr %First2, align 4
 // CHECK-NEXT:ret i32 %0
 
-// CHECK:     define linkonce_odr noundef i32 @"?getSecond@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #2 align 2 {
+// CHECK:     define linkonce_odr noundef i32 @"?getSecond@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #0 align 2 {
 // CHECK-NEXT:entry:
 // CHECK-NEXT:%this.addr = alloca ptr, align 4
 // CHECK-NEXT:%agg.tmp = alloca %struct.Pair, align 4
diff --git a/clang/test/CodeGenHLSL/this-assignment.hlsl b/clang/test/CodeGenHLSL/this-assignment.hlsl
@@ -24,7 +24,7 @@ void main() {
 }
 
 // This tests reference like implicit this in HLSL
-// CHECK:     define linkonce_odr noundef i32 @"?getFirst@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #3 align 2 {
+// CHECK:     define linkonce_odr noundef i32 @"?getFirst@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #0 align 2 {
 // CHECK-NEXT:entry:
 // CHECK-NEXT:%this.addr = alloca ptr, align 4
 // CHECK-NEXT:%Another = alloca %struct.Pair, align 4
@@ -34,7 +34,7 @@ void main() {
 // CHECK-NEXT:call void @llvm.memcpy.p0.p0.i32(ptr align 4 %this1, ptr align 4 %Another, i32 8, i1 false)
 // CHECK-NEXT:%First = getelementptr inbounds nuw %struct.Pair, ptr %this1, i32 0, i32 0
 
-// CHECK:     define linkonce_odr noundef i32 @"?getSecond@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #3 align 2 {
+// CHECK:     define linkonce_odr noundef i32 @"?getSecond@Pair@@QAAHXZ"(ptr noundef nonnull align 4 dereferenceable(8) %this) #0 align 2 {
 // CHECK-NEXT:entry:
 // CHECK-NEXT:%this.addr = alloca ptr, align 4
 // CHECK-NEXT:%ref.tmp = alloca %struct.Pair, align 4
