[clang] [llvm] [clang][HLSL][SPRI-V] Add convergence intrinsics (PR #80680)
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Mon Mar 11 09:50:16 PDT 2024
Nathan =?utf-8?q?Gauër?= <brioche at google.com>,
Nathan =?utf-8?q?Gauër?= <brioche at google.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/80680 at github.com>
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-codegen
@llvm/pr-subscribers-clang
Author: Nathan Gauër (Keenuts)
<details>
<summary>Changes</summary>
HLSL has wave operations and other kind of function which required the control flow to either be converged, or respect certain constraints as where and how to re-converge.
At the HLSL level, the convergence are mostly obvious: the control flow is expected to re-converge at the end of a scope.
Once translated to IR, HLSL scopes disapear. This means we need a way to communicate convergence restrictions down to the backend.
For this, the SPIR-V backend uses convergence intrinsics. So this commit adds some code to generate convergence intrinsics when required.
This commit is not to be submitted as-is (lacks testing), but should serve as a basis for an upcoming RFC.
---
Full diff: https://github.com/llvm/llvm-project/pull/80680.diff
10 Files Affected:
- (modified) clang/include/clang/Basic/Builtins.td (+7)
- (modified) clang/lib/CodeGen/CGBuiltin.cpp (+97)
- (modified) clang/lib/CodeGen/CGCall.cpp (+4)
- (modified) clang/lib/CodeGen/CGLoopInfo.h (+7-1)
- (modified) clang/lib/CodeGen/CodeGenFunction.h (+19)
- (modified) clang/lib/Headers/hlsl/hlsl_intrinsics.h (+5)
- (added) clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl (+40)
- (added) clang/test/CodeGenHLSL/builtins/wave_get_lane_index_simple.hlsl (+14)
- (added) clang/test/CodeGenHLSL/builtins/wave_get_lane_index_subcall.hlsl (+21)
- (modified) llvm/include/llvm/IR/IntrinsicInst.h (+13)
``````````diff
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index 9c703377ca8d3e..11c857cfa3f374 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -4554,6 +4554,13 @@ def HLSLWaveActiveCountBits : LangBuiltin<"HLSL_LANG"> {
let Prototype = "unsigned int(bool)";
}
+// HLSL
+def HLSLWaveGetLaneIndex : LangBuiltin<"HLSL_LANG"> {
+ let Spellings = ["__builtin_hlsl_wave_get_lane_index"];
+ let Attributes = [NoThrow, Const];
+ let Prototype = "unsigned int()";
+}
+
def HLSLCreateHandle : LangBuiltin<"HLSL_LANG"> {
let Spellings = ["__builtin_hlsl_create_handle"];
let Attributes = [NoThrow, Const];
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 20c35757939152..12fc855fb92bb8 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -1130,8 +1130,96 @@ struct BitTest {
static BitTest decodeBitTestBuiltin(unsigned BuiltinID);
};
+
+// Returns the first convergence entry/loop/anchor instruction found in |BB|.
+// std::nullopt otherwise.
+std::optional<llvm::IntrinsicInst *> getConvergenceToken(llvm::BasicBlock *BB) {
+ for (auto &I : *BB) {
+ auto *II = dyn_cast<llvm::IntrinsicInst>(&I);
+ if (II && isConvergenceControlIntrinsic(II->getIntrinsicID()))
+ return II;
+ }
+ return std::nullopt;
+}
+
} // namespace
+llvm::CallBase *
+CodeGenFunction::AddConvergenceControlAttr(llvm::CallBase *Input,
+ llvm::Value *ParentToken) {
+ llvm::Value *bundleArgs[] = {ParentToken};
+ llvm::OperandBundleDef OB("convergencectrl", bundleArgs);
+ auto Output = llvm::CallBase::addOperandBundle(
+ Input, llvm::LLVMContext::OB_convergencectrl, OB, Input);
+ Input->replaceAllUsesWith(Output);
+ Input->eraseFromParent();
+ return Output;
+}
+
+llvm::IntrinsicInst *
+CodeGenFunction::EmitConvergenceLoop(llvm::BasicBlock *BB,
+ llvm::Value *ParentToken) {
+ CGBuilderTy::InsertPoint IP = Builder.saveIP();
+ Builder.SetInsertPoint(&BB->front());
+ auto CB = Builder.CreateIntrinsic(
+ llvm::Intrinsic::experimental_convergence_loop, {}, {});
+ Builder.restoreIP(IP);
+
+ auto I = AddConvergenceControlAttr(CB, ParentToken);
+ // Controlled convergence is incompatible with uncontrolled convergence.
+ // Removing any old attributes.
+ I->setNotConvergent();
+
+ return cast<llvm::IntrinsicInst>(I);
+}
+
+llvm::IntrinsicInst *
+CodeGenFunction::getOrEmitConvergenceEntryToken(llvm::Function *F) {
+ auto *BB = &F->getEntryBlock();
+ auto token = getConvergenceToken(BB);
+ if (token.has_value())
+ return token.value();
+
+ // Adding a convergence token requires the function to be marked as
+ // convergent.
+ F->setConvergent();
+
+ CGBuilderTy::InsertPoint IP = Builder.saveIP();
+ Builder.SetInsertPoint(&BB->front());
+ auto I = Builder.CreateIntrinsic(
+ llvm::Intrinsic::experimental_convergence_entry, {}, {});
+ assert(isa<llvm::IntrinsicInst>(I));
+ Builder.restoreIP(IP);
+
+ return cast<llvm::IntrinsicInst>(I);
+}
+
+llvm::IntrinsicInst *
+CodeGenFunction::getOrEmitConvergenceLoopToken(const LoopInfo *LI) {
+ assert(LI != nullptr);
+
+ auto token = getConvergenceToken(LI->getHeader());
+ if (token.has_value())
+ return *token;
+
+ llvm::IntrinsicInst *PII =
+ LI->getParent()
+ ? EmitConvergenceLoop(LI->getHeader(),
+ getOrEmitConvergenceLoopToken(LI->getParent()))
+ : getOrEmitConvergenceEntryToken(LI->getHeader()->getParent());
+
+ return EmitConvergenceLoop(LI->getHeader(), PII);
+}
+
+llvm::CallBase *
+CodeGenFunction::AddControlledConvergenceAttr(llvm::CallBase *Input) {
+ llvm::Value *ParentToken =
+ LoopStack.hasInfo()
+ ? getOrEmitConvergenceLoopToken(&LoopStack.getInfo())
+ : getOrEmitConvergenceEntryToken(Input->getFunction());
+ return AddConvergenceControlAttr(Input, ParentToken);
+}
+
BitTest BitTest::decodeBitTestBuiltin(unsigned BuiltinID) {
switch (BuiltinID) {
// Main portable variants.
@@ -5698,6 +5786,15 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
{NDRange, Kernel, Block}));
}
+ case Builtin::BI__builtin_hlsl_wave_get_lane_index: {
+ auto *CI = EmitRuntimeCall(CGM.CreateRuntimeFunction(
+ llvm::FunctionType::get(IntTy, {}, false), "__hlsl_wave_get_lane_index",
+ {}, false, true));
+ if (getTarget().getTriple().isSPIRVLogical())
+ CI = dyn_cast<CallInst>(AddControlledConvergenceAttr(CI));
+ return RValue::get(CI);
+ }
+
case Builtin::BI__builtin_store_half:
case Builtin::BI__builtin_store_halff: {
Value *Val = EmitScalarExpr(E->getArg(0));
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index a28d7888715d85..4b24367a8e19d9 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -5686,6 +5686,10 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
if (!CI->getType()->isVoidTy())
CI->setName("call");
+ if (getTarget().getTriple().isSPIRVLogical() &&
+ CI->getCalledFunction()->isConvergent())
+ CI = AddControlledConvergenceAttr(CI);
+
// Update largest vector width from the return type.
LargestVectorWidth =
std::max(LargestVectorWidth, getMaxVectorWidth(CI->getType()));
diff --git a/clang/lib/CodeGen/CGLoopInfo.h b/clang/lib/CodeGen/CGLoopInfo.h
index a1c8c7e5307fd9..7c2f7443bd3c99 100644
--- a/clang/lib/CodeGen/CGLoopInfo.h
+++ b/clang/lib/CodeGen/CGLoopInfo.h
@@ -110,6 +110,10 @@ class LoopInfo {
/// been processed.
void finish();
+ /// Returns the first outer loop containing this loop if any, nullptr
+ /// otherwise.
+ const LoopInfo *getParent() const { return Parent; }
+
private:
/// Loop ID metadata.
llvm::TempMDTuple TempLoopID;
@@ -291,12 +295,14 @@ class LoopInfoStack {
/// Set no progress for the next loop pushed.
void setMustProgress(bool P) { StagedAttrs.MustProgress = P; }
-private:
/// Returns true if there is LoopInfo on the stack.
bool hasInfo() const { return !Active.empty(); }
+
/// Return the LoopInfo for the current loop. HasInfo should be called
/// first to ensure LoopInfo is present.
const LoopInfo &getInfo() const { return *Active.back(); }
+
+private:
/// The set of attributes that will be applied to the next pushed loop.
LoopAttributes StagedAttrs;
/// Stack of active loops.
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 6c825a302913df..c475b80db0fc41 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4868,6 +4868,25 @@ class CodeGenFunction : public CodeGenTypeCache {
llvm::Value *emitBoolVecConversion(llvm::Value *SrcVec,
unsigned NumElementsDst,
const llvm::Twine &Name = "");
+ // Adds a convergence_ctrl attribute to |Input| and emits the required parent
+ // convergence instructions.
+ llvm::CallBase *AddControlledConvergenceAttr(llvm::CallBase *Input);
+
+private:
+ // Emits a convergence_loop instruction for the given |BB|, with |ParentToken|
+ // as it's parent convergence instr.
+ llvm::IntrinsicInst *EmitConvergenceLoop(llvm::BasicBlock *BB,
+ llvm::Value *ParentToken);
+ // Adds a convergence_ctrl attribute with |ParentToken| as parent convergence
+ // instr to the call |Input|.
+ llvm::CallBase *AddConvergenceControlAttr(llvm::CallBase *Input,
+ llvm::Value *ParentToken);
+ // Find the convergence_entry instruction |F|, or emits ones if none exists.
+ // Returns the convergence instruction.
+ llvm::IntrinsicInst *getOrEmitConvergenceEntryToken(llvm::Function *F);
+ // Find the convergence_loop instruction for the loop defined by |LI|, or
+ // emits one if none exists. Returns the convergence instruction.
+ llvm::IntrinsicInst *getOrEmitConvergenceLoopToken(const LoopInfo *LI);
private:
llvm::MDNode *getRangeForLoadFromType(QualType Ty);
diff --git a/clang/lib/Headers/hlsl/hlsl_intrinsics.h b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
index 45f8544392584e..108588e5e0af60 100644
--- a/clang/lib/Headers/hlsl/hlsl_intrinsics.h
+++ b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
@@ -1297,5 +1297,10 @@ _HLSL_AVAILABILITY(shadermodel, 6.0)
_HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_active_count_bits)
uint WaveActiveCountBits(bool Val);
+/// \brief Returns the index of the current lane within the current wave.
+_HLSL_AVAILABILITY(shadermodel, 6.0)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_get_lane_index)
+uint WaveGetLaneIndex();
+
} // namespace hlsl
#endif //_HLSL_HLSL_INTRINSICS_H_
diff --git a/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl
new file mode 100644
index 00000000000000..9481b0d60a2723
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_do_while.hlsl
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: spirv-pc-vulkan-library %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+
+// CHECK: define spir_func void @main() [[A0:#[0-9]+]] {
+void main() {
+// CHECK: entry:
+// CHECK: %[[CT_ENTRY:[0-9]+]] = call token @llvm.experimental.convergence.entry()
+// CHECK: br label %[[LABEL_WHILE_COND:.+]]
+ int cond = 0;
+
+// CHECK: [[LABEL_WHILE_COND]]:
+// CHECK: %[[CT_LOOP:[0-9]+]] = call token @llvm.experimental.convergence.loop() [ "convergencectrl"(token %[[CT_ENTRY]]) ]
+// CHECK: br label %[[LABEL_WHILE_BODY:.+]]
+ while (true) {
+
+// CHECK: [[LABEL_WHILE_BODY]]:
+// CHECK: br i1 {{%.+}}, label %[[LABEL_IF_THEN:.+]], label %[[LABEL_IF_END:.+]]
+
+// CHECK: [[LABEL_IF_THEN]]:
+// CHECK: call i32 @__hlsl_wave_get_lane_index() [ "convergencectrl"(token %[[CT_LOOP]]) ]
+// CHECK: br label %[[LABEL_WHILE_END:.+]]
+ if (cond == 2) {
+ uint index = WaveGetLaneIndex();
+ break;
+ }
+
+// CHECK: [[LABEL_IF_END]]:
+// CHECK: br label %[[LABEL_WHILE_COND]]
+ cond++;
+ }
+
+// CHECK: [[LABEL_WHILE_END]]:
+// CHECK: ret void
+}
+
+// CHECK-DAG: declare i32 @__hlsl_wave_get_lane_index() [[A1:#[0-9]+]]
+
+// CHECK-DAG: attributes [[A0]] = {{{.*}}convergent{{.*}}}
+// CHECK-DAG: attributes [[A1]] = {{{.*}}convergent{{.*}}}
+
diff --git a/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_simple.hlsl b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_simple.hlsl
new file mode 100644
index 00000000000000..8f52d81091c180
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_simple.hlsl
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: spirv-pc-vulkan-library %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+
+// CHECK: define spir_func noundef i32 @_Z6test_1v() [[A0:#[0-9]+]] {
+// CHECK: %[[CI:[0-9]+]] = call token @llvm.experimental.convergence.entry()
+// CHECK: call i32 @__hlsl_wave_get_lane_index() [ "convergencectrl"(token %[[CI]]) ]
+uint test_1() {
+ return WaveGetLaneIndex();
+}
+
+// CHECK: declare i32 @__hlsl_wave_get_lane_index() [[A1:#[0-9]+]]
+
+// CHECK-DAG: attributes [[A0]] = { {{.*}}convergent{{.*}} }
+// CHECK-DAG: attributes [[A1]] = { {{.*}}convergent{{.*}} }
diff --git a/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_subcall.hlsl b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_subcall.hlsl
new file mode 100644
index 00000000000000..379c8f118f52f3
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/wave_get_lane_index_subcall.hlsl
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: spirv-pc-vulkan-library %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+
+// CHECK: define spir_func noundef i32 @_Z6test_1v() [[A0:#[0-9]+]] {
+// CHECK: %[[C1:[0-9]+]] = call token @llvm.experimental.convergence.entry()
+// CHECK: call i32 @__hlsl_wave_get_lane_index() [ "convergencectrl"(token %[[C1]]) ]
+uint test_1() {
+ return WaveGetLaneIndex();
+}
+
+// CHECK-DAG: declare i32 @__hlsl_wave_get_lane_index() [[A1:#[0-9]+]]
+
+// CHECK: define spir_func noundef i32 @_Z6test_2v() [[A0]] {
+// CHECK: %[[C2:[0-9]+]] = call token @llvm.experimental.convergence.entry()
+// CHECK: call spir_func noundef i32 @_Z6test_1v() [ "convergencectrl"(token %[[C2]]) ]
+uint test_2() {
+ return test_1();
+}
+
+// CHECK-DAG: attributes [[A0]] = {{{.*}}convergent{{.*}}}
+// CHECK-DAG: attributes [[A1]] = {{{.*}}convergent{{.*}}}
diff --git a/llvm/include/llvm/IR/IntrinsicInst.h b/llvm/include/llvm/IR/IntrinsicInst.h
index c07b83a81a63e1..4f22720f1c558d 100644
--- a/llvm/include/llvm/IR/IntrinsicInst.h
+++ b/llvm/include/llvm/IR/IntrinsicInst.h
@@ -1782,6 +1782,19 @@ class ConvergenceControlInst : public IntrinsicInst {
static bool classof(const Value *V) {
return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
}
+
+ // Returns the convergence intrinsic referenced by |I|'s convergencectrl
+ // attribute if any.
+ static IntrinsicInst *getParentConvergenceToken(Instruction *I) {
+ auto *CI = dyn_cast<llvm::CallInst>(I);
+ if (!CI)
+ return nullptr;
+
+ auto Bundle = CI->getOperandBundle(llvm::LLVMContext::OB_convergencectrl);
+ assert(Bundle->Inputs.size() == 1 &&
+ Bundle->Inputs[0]->getType()->isTokenTy());
+ return dyn_cast<llvm::IntrinsicInst>(Bundle->Inputs[0].get());
+ }
};
} // end namespace llvm
``````````
</details>
https://github.com/llvm/llvm-project/pull/80680
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