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[HLSL] Re-implement countbits with the correct return type #113189

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Merged
merged 5 commits into from
Oct 29, 2024
Merged

[HLSL] Re-implement countbits with the correct return type #113189

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23d6202
implement countbits correctly
spall Oct 16, 2024
e29f401
make clang format happy
spall Oct 21, 2024
5e40350
address PR comments
spall Oct 23, 2024
74f0925
address latest pr comments + extra tests
spall Oct 24, 2024
d160782
remove use of constexpr and replace with const inline
spall Oct 28, 2024
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124 changes: 73 additions & 51 deletions clang/lib/Headers/hlsl/hlsl_intrinsics.h
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Original file line number Diff line number Diff line change
Expand Up @@ -723,66 +723,88 @@ float4 cosh(float4);

#ifdef __HLSL_ENABLE_16_BIT
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int16_t countbits(int16_t);
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Sorry I missed the earlier PR where this was added, but I don't know how signed integers work here. We only support unsigned in HLSL. Is that a change for clang?
Missing tests as well, if so.

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When I asked Justin about this he pointed to this link:
https://github.com/microsoft/DirectXShaderCompiler/blob/main/utils/hct/gen_intrin_main.txt#L114
and suggested it meant both signed and unsigned were supported.

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Ah, of course our documentation is wrong. countbits of signed is kind of illogical, but definitely should add tests regardless.

const inline uint countbits(int16_t x) {
return __builtin_elementwise_popcount(x);
}
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int16_t2 countbits(int16_t2);
const inline uint2 countbits(int16_t2 x) {
return __builtin_elementwise_popcount(x);
}
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int16_t3 countbits(int16_t3);
const inline uint3 countbits(int16_t3 x) {
return __builtin_elementwise_popcount(x);
}
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int16_t4 countbits(int16_t4);
const inline uint4 countbits(int16_t4 x) {
return __builtin_elementwise_popcount(x);
}
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint16_t countbits(uint16_t);
const inline uint countbits(uint16_t x) {
return __builtin_elementwise_popcount(x);
}
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint16_t2 countbits(uint16_t2);
const inline uint2 countbits(uint16_t2 x) {
return __builtin_elementwise_popcount(x);
}
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint16_t3 countbits(uint16_t3);
const inline uint3 countbits(uint16_t3 x) {
return __builtin_elementwise_popcount(x);
}
_HLSL_AVAILABILITY(shadermodel, 6.2)
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint16_t4 countbits(uint16_t4);
const inline uint4 countbits(uint16_t4 x) {
return __builtin_elementwise_popcount(x);
}
#endif

_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int countbits(int);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int2 countbits(int2);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int3 countbits(int3);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int4 countbits(int4);

_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint countbits(uint);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint2 countbits(uint2);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint3 countbits(uint3);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint4 countbits(uint4);

_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int64_t countbits(int64_t);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int64_t2 countbits(int64_t2);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int64_t3 countbits(int64_t3);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
int64_t4 countbits(int64_t4);

_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint64_t countbits(uint64_t);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint64_t2 countbits(uint64_t2);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint64_t3 countbits(uint64_t3);
_HLSL_BUILTIN_ALIAS(__builtin_elementwise_popcount)
uint64_t4 countbits(uint64_t4);
const inline uint countbits(int x) { return __builtin_elementwise_popcount(x); }
const inline uint2 countbits(int2 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint3 countbits(int3 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint4 countbits(int4 x) {
return __builtin_elementwise_popcount(x);
}

const inline uint countbits(uint x) {
return __builtin_elementwise_popcount(x);
}
const inline uint2 countbits(uint2 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint3 countbits(uint3 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint4 countbits(uint4 x) {
return __builtin_elementwise_popcount(x);
}

const inline uint countbits(int64_t x) {
return __builtin_elementwise_popcount(x);
}
const inline uint2 countbits(int64_t2 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint3 countbits(int64_t3 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint4 countbits(int64_t4 x) {
return __builtin_elementwise_popcount(x);
}

const inline uint countbits(uint64_t x) {
return __builtin_elementwise_popcount(x);
}
const inline uint2 countbits(uint64_t2 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint3 countbits(uint64_t3 x) {
return __builtin_elementwise_popcount(x);
}
const inline uint4 countbits(uint64_t4 x) {
return __builtin_elementwise_popcount(x);
}

//===----------------------------------------------------------------------===//
// degrees builtins
Expand Down
62 changes: 45 additions & 17 deletions clang/test/CodeGenHLSL/builtins/countbits.hlsl
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Expand Up @@ -4,34 +4,51 @@

#ifdef __HLSL_ENABLE_16_BIT
// CHECK-LABEL: test_countbits_ushort
// CHECK: call i16 @llvm.ctpop.i16
uint16_t test_countbits_ushort(uint16_t p0)
// CHECK: [[A:%.*]] = call i16 @llvm.ctpop.i16
// CHECK-NEXT: zext i16 [[A]] to i32
uint test_countbits_ushort(uint16_t p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_short
// CHECK: [[A:%.*]] = call i16 @llvm.ctpop.i16
// CHECK-NEXT: sext i16 [[A]] to i32
uint test_countbits_short(int16_t p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_ushort2
// CHECK: call <2 x i16> @llvm.ctpop.v2i16
uint16_t2 test_countbits_ushort2(uint16_t2 p0)
// CHECK: [[A:%.*]] = call <2 x i16> @llvm.ctpop.v2i16
// CHECK-NEXT: zext <2 x i16> [[A]] to <2 x i32>
uint2 test_countbits_ushort2(uint16_t2 p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_ushort3
// CHECK: call <3 x i16> @llvm.ctpop.v3i16
uint16_t3 test_countbits_ushort3(uint16_t3 p0)
// CHECK: [[A:%.*]] = call <3 x i16> @llvm.ctpop.v3i16
// CHECK-NEXT: zext <3 x i16> [[A]] to <3 x i32>
uint3 test_countbits_ushort3(uint16_t3 p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_ushort4
// CHECK: call <4 x i16> @llvm.ctpop.v4i16
uint16_t4 test_countbits_ushort4(uint16_t4 p0)
// CHECK: [[A:%.*]] = call <4 x i16> @llvm.ctpop.v4i16
// CHECK-NEXT: zext <4 x i16> [[A]] to <4 x i32>
uint4 test_countbits_ushort4(uint16_t4 p0)
{
return countbits(p0);
}
#endif

// CHECK-LABEL: test_countbits_uint
// CHECK: call i32 @llvm.ctpop.i32
int test_countbits_uint(uint p0)
uint test_countbits_uint(uint p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_int
// CHECK: call i32 @llvm.ctpop.i32
uint test_countbits_int(int p0)
{
return countbits(p0);
}
Expand All @@ -55,26 +72,37 @@ uint4 test_countbits_uint4(uint4 p0)
}

// CHECK-LABEL: test_countbits_long
// CHECK: call i64 @llvm.ctpop.i64
uint64_t test_countbits_long(uint64_t p0)
// CHECK: [[A:%.*]] = call i64 @llvm.ctpop.i64
// CHECK-NEXT: trunc i64 [[A]] to i32
uint test_countbits_long(uint64_t p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_slong
// CHECK: [[A:%.*]] = call i64 @llvm.ctpop.i64
// CHECK-NEXT: trunc i64 [[A]] to i32
uint test_countbits_slong(int64_t p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_long2
// CHECK: call <2 x i64> @llvm.ctpop.v2i64
uint64_t2 test_countbits_long2(uint64_t2 p0)
// CHECK: [[A:%.*]] = call <2 x i64> @llvm.ctpop.v2i64
// CHECK-NEXT: trunc <2 x i64> [[A]] to <2 x i32>
uint2 test_countbits_long2(uint64_t2 p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_long3
// CHECK: call <3 x i64> @llvm.ctpop.v3i64
uint64_t3 test_countbits_long3(uint64_t3 p0)
// CHECK: [[A:%.*]] = call <3 x i64> @llvm.ctpop.v3i64
// CHECK-NEXT: trunc <3 x i64> [[A]] to <3 x i32>
uint3 test_countbits_long3(uint64_t3 p0)
{
return countbits(p0);
}
// CHECK-LABEL: test_countbits_long4
// CHECK: call <4 x i64> @llvm.ctpop.v4i64
uint64_t4 test_countbits_long4(uint64_t4 p0)
// CHECK: [[A:%.*]] = call <4 x i64> @llvm.ctpop.v4i64
// CHECK-NEXT: trunc <4 x i64> [[A]] to <4 x i32>
uint4 test_countbits_long4(uint64_t4 p0)
{
return countbits(p0);
}
14 changes: 5 additions & 9 deletions clang/test/SemaHLSL/BuiltIns/countbits-errors.hlsl
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@@ -1,6 +1,4 @@
// RUN: %clang_cc1 -finclude-default-header
// -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm-only
// -disable-llvm-passes -verify -verify-ignore-unexpected
// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm-only -disable-llvm-passes -verify -verify-ignore-unexpected


double test_int_builtin(double p0) {
Expand All @@ -9,13 +7,11 @@ double test_int_builtin(double p0) {
}

double2 test_int_builtin_2(double2 p0) {
return __builtin_elementwise_popcount(p0);
// expected-error@-1 {{1st argument must be a vector of integers
// (was 'double2' (aka 'vector<double, 2>'))}}
return countbits(p0);
// expected-error@-1 {{call to 'countbits' is ambiguous}}
}

double test_int_builtin_3(float p0) {
return __builtin_elementwise_popcount(p0);
// expected-error@-1 {{1st argument must be a vector of integers
// (was 'float')}}
return countbits(p0);
// expected-error@-1 {{call to 'countbits' is ambiguous}}
}
5 changes: 2 additions & 3 deletions llvm/lib/Target/DirectX/DXIL.td
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Original file line number Diff line number Diff line change
Expand Up @@ -554,11 +554,10 @@ def Rbits : DXILOp<30, unary> {
let attributes = [Attributes<DXIL1_0, [ReadNone]>];
}

def CBits : DXILOp<31, unary> {
def CountBits : DXILOp<31, unaryBits> {
let Doc = "Returns the number of 1 bits in the specified value.";
let LLVMIntrinsic = int_ctpop;
let arguments = [OverloadTy];
let result = OverloadTy;
let result = Int32Ty;
let overloads =
[Overloads<DXIL1_0, [Int16Ty, Int32Ty, Int64Ty]>];
let stages = [Stages<DXIL1_0, [all_stages]>];
Expand Down
70 changes: 70 additions & 0 deletions llvm/lib/Target/DirectX/DXILOpLowering.cpp
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Expand Up @@ -505,6 +505,73 @@ class OpLowerer {
});
}

[[nodiscard]] bool lowerCtpopToCountBits(Function &F) {
IRBuilder<> &IRB = OpBuilder.getIRB();
Type *Int32Ty = IRB.getInt32Ty();

return replaceFunction(F, [&](CallInst *CI) -> Error {
IRB.SetInsertPoint(CI);
SmallVector<Value *> Args;
Args.append(CI->arg_begin(), CI->arg_end());

Type *RetTy = Int32Ty;
Type *FRT = F.getReturnType();
if (const auto *VT = dyn_cast<VectorType>(FRT))
RetTy = VectorType::get(RetTy, VT);

Expected<CallInst *> OpCall = OpBuilder.tryCreateOp(
dxil::OpCode::CountBits, Args, CI->getName(), RetTy);
if (Error E = OpCall.takeError())
return E;

// If the result type is 32 bits we can do a direct replacement.
if (FRT->isIntOrIntVectorTy(32)) {
CI->replaceAllUsesWith(*OpCall);
CI->eraseFromParent();
return Error::success();
}

unsigned CastOp;
unsigned CastOp2;
if (FRT->isIntOrIntVectorTy(16)) {
CastOp = Instruction::ZExt;
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Related to the signed vs unsigned: this is where things I think get confusing. int16_t would almost always be sign extended, not zero extended. But doing a sign extension here doesn't make sense as you'll count 16 extra bits for any negative int16_t.
I think this is why std::bitset basically ignores the type. It's a forcing function to the author to say "yes, I'm purposely counting a signed value now go away"

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Sorry if I'm being confusing - I am not saying you have the wrong code here, I'm just bringing it up that this is where my thought drifted towards the topic because of this zero extension (which I think is correct)

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The extension should only be on the return value which is always unsigned. Is this code wrong with that in mind?

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Oh, I see. This is overriding the cast op below. Is a zero/sign extension needed? I notice the return type is "int16_t".
Although I guess that's another question - should the return types all be 32 bits? i.e., "int_t"

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@bfavela bfavela Oct 21, 2024 •
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Disregard. I see you actually updated that correctly! (the whole point of this PR haha)

CastOp2 = Instruction::SExt;
} else { // must be 64 bits
assert(FRT->isIntOrIntVectorTy(64) &&
"Currently only lowering 16, 32, or 64 bit ctpop to CountBits \
is supported.");
CastOp = Instruction::Trunc;
CastOp2 = Instruction::Trunc;
}

// It is correct to replace the ctpop with the dxil op and
// remove all casts to i32
bool NeedsCast = false;
for (User *User : make_early_inc_range(CI->users())) {
Instruction *I = dyn_cast<Instruction>(User);
if (I && (I->getOpcode() == CastOp || I->getOpcode() == CastOp2) &&
I->getType() == RetTy) {
I->replaceAllUsesWith(*OpCall);
I->eraseFromParent();
} else
NeedsCast = true;
}

// It is correct to replace a ctpop with the dxil op and
// a cast from i32 to the return type of the ctpop
// the cast is emitted here if there is a non-cast to i32
// instr which uses the ctpop
if (NeedsCast) {
Value *Cast =
IRB.CreateZExtOrTrunc(*OpCall, F.getReturnType(), "ctpop.cast");
CI->replaceAllUsesWith(Cast);
}

CI->eraseFromParent();
return Error::success();
});
}

bool lowerIntrinsics() {
bool Updated = false;
bool HasErrors = false;
Expand Down Expand Up @@ -543,6 +610,9 @@ class OpLowerer {
return replaceSplitDoubleCallUsages(CI, Op);
});
break;
case Intrinsic::ctpop:
HasErrors |= lowerCtpopToCountBits(F);
break;
}
Updated = true;
}
Expand Down
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