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[HLSL] Shore up floating point conversions
This PR fixes bugs in HLSL floating conversions. HLSL always has `half`, `float` and `double` types, which promote in the order: `half`->`float`->`double` and convert in the order: `double`->`float`->`half` As with other conversions in C++, promotions are preferred over conversions. We do have floating conversions documented in the draft language specification (https://microsoft.github.io/hlsl-specs/specs/hlsl.pdf [Conv.rank.float]) although the exact language is still in flux (microsoft/hlsl-specs#206). Resolves llvm#81047
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‎clang/lib/Sema/SemaOverload.cpp

Lines changed: 42 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2587,7 +2587,8 @@ bool Sema::IsIntegralPromotion(Expr *From, QualType FromType, QualType ToType) {
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25882588
// In HLSL an rvalue of integral type can be promoted to an rvalue of a larger
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// integral type.
2590-
if (Context.getLangOpts().HLSL)
2590+
if (Context.getLangOpts().HLSL && FromType->isIntegerType() &&
2591+
ToType->isIntegerType())
25912592
return Context.getTypeSize(FromType) < Context.getTypeSize(ToType);
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25932594
return false;
@@ -2616,6 +2617,13 @@ bool Sema::IsFloatingPointPromotion(QualType FromType, QualType ToType) {
26162617
ToBuiltin->getKind() == BuiltinType::Ibm128))
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return true;
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// In HLSL, `half` promotes to `float` or `double`, regardless of whether
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// or not native half types are enabled.
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if (getLangOpts().HLSL && FromBuiltin->getKind() == BuiltinType::Half &&
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(ToBuiltin->getKind() == BuiltinType::Float ||
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ToBuiltin->getKind() == BuiltinType::Double))
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return true;
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// Half can be promoted to float.
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if (!getLangOpts().NativeHalfType &&
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FromBuiltin->getKind() == BuiltinType::Half &&
@@ -4393,6 +4401,24 @@ getFixedEnumPromtion(Sema &S, const StandardConversionSequence &SCS) {
43934401
return FixedEnumPromotion::ToPromotedUnderlyingType;
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}
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static ImplicitConversionSequence::CompareKind
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HLSLCompareFloatingRank(QualType LHS, QualType RHS) {
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assert(LHS->isVectorType() == RHS->isVectorType() &&
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"Either both elements should be vectors or neither should.");
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if (const auto *VT = LHS->getAs<VectorType>())
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LHS = VT->getElementType();
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4411+
if (const auto *VT = RHS->getAs<VectorType>())
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RHS = VT->getElementType();
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const auto L = LHS->getAs<BuiltinType>()->getKind();
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const auto R = RHS->getAs<BuiltinType>()->getKind();
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if (L == R)
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return ImplicitConversionSequence::Indistinguishable;
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return L < R ? ImplicitConversionSequence::Better
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: ImplicitConversionSequence::Worse;
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}
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/// CompareStandardConversionSequences - Compare two standard
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/// conversion sequences to determine whether one is better than the
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/// other or if they are indistinguishable (C++ 13.3.3.2p3).
@@ -4634,6 +4660,21 @@ CompareStandardConversionSequences(Sema &S, SourceLocation Loc,
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: ImplicitConversionSequence::Worse;
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}
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4663+
if (S.getLangOpts().HLSL) {
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// On a promotion we prefer the lower rank to disambiguate.
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if ((SCS1.Second == ICK_Floating_Promotion &&
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SCS2.Second == ICK_Floating_Promotion) ||
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(SCS1.Element == ICK_Floating_Promotion &&
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SCS2.Element == ICK_Floating_Promotion))
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return HLSLCompareFloatingRank(SCS1.getToType(2), SCS2.getToType(2));
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// On a conversion we prefer the higher rank to disambiguate.
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if ((SCS1.Second == ICK_Floating_Conversion &&
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SCS2.Second == ICK_Floating_Conversion) ||
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(SCS1.Element == ICK_Floating_Conversion &&
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SCS2.Element == ICK_Floating_Conversion))
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return HLSLCompareFloatingRank(SCS2.getToType(2), SCS1.getToType(2));
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}
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return ImplicitConversionSequence::Indistinguishable;
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}
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‎clang/test/SemaHLSL/ScalarOverloadResolution.hlsl

Lines changed: 229 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,229 @@
1+
// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-library -fnative-half-type -finclude-default-header -Wconversion -verify -o - %s
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// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-library -fnative-half-type -finclude-default-header -ast-dump %s | FileCheck %s
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// This test verifies floating point type implicit conversion ranks for overload
5+
// resolution. In HLSL the built-in type ranks are half < float < double. This
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// applies to both scalar and vector types.
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// HLSL allows implicit truncation fo types, so it differentiates between
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// promotions (converting to larger types) and conversions (converting to
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// smaller types). Promotions are preferred over conversions. Promotions prefer
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// promoting to the next lowest type in the ranking order. Conversions prefer
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// converting to the next highest type in the ranking order.
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void HalfFloatDouble(double D);
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void HalfFloatDouble(float F);
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void HalfFloatDouble(half H);
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// CHECK: FunctionDecl {{.*}} used HalfFloatDouble 'void (double)'
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// CHECK: FunctionDecl {{.*}} used HalfFloatDouble 'void (float)'
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// CHECK: FunctionDecl {{.*}} used HalfFloatDouble 'void (half)'
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void FloatDouble(double D);
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void FloatDouble(float F);
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// CHECK: FunctionDecl {{.*}} used FloatDouble 'void (double)'
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// CHECK: FunctionDecl {{.*}} used FloatDouble 'void (float)'
27+
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void HalfDouble(double D);
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void HalfDouble(half H);
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// CHECK: FunctionDecl {{.*}} used HalfDouble 'void (double)'
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// CHECK: FunctionDecl {{.*}} used HalfDouble 'void (half)'
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void HalfFloat(float F);
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void HalfFloat(half H);
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// CHECK: FunctionDecl {{.*}} used HalfFloat 'void (float)'
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// CHECK: FunctionDecl {{.*}} used HalfFloat 'void (half)'
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void Double(double D);
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void Float(float F);
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void Half(half H);
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// CHECK: FunctionDecl {{.*}} used Double 'void (double)'
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// CHECK: FunctionDecl {{.*}} used Float 'void (float)'
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// CHECK: FunctionDecl {{.*}} used Half 'void (half)'
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// Case 1: A function declared with overloads for half float and double types.
50+
// (a) When called with half, it will resolve to half because half is an exact
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// match.
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// (b) When called with float it will resolve to float because float is an
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// exact match.
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// (c) When called with double it will resolve to double because it is an
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// exact match.
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// CHECK: FunctionDecl {{.*}} Case1 'void (half, float, double)'
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void Case1(half H, float F, double D) {
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(half)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (half)' lvalue Function {{.*}} 'HalfFloatDouble' 'void (half)'
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HalfFloatDouble(H);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'HalfFloatDouble' 'void (float)'
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HalfFloatDouble(F);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(double)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (double)' lvalue Function {{.*}} 'HalfFloatDouble' 'void (double)'
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HalfFloatDouble(D);
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}
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75+
// Case 2: A function declared with double and float overlaods.
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// (a) When called with half, it will resolve to float because float is lower
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// ranked than double.
78+
// (b) When called with float it will resolve to float because float is an
79+
// exact match.
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// (c) When called with double it will resolve to double because it is an
81+
// exact match.
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83+
// CHECK: FunctionDecl {{.*}} Case2 'void (half, float, double)'
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void Case2(half H, float F, double D) {
85+
// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'FloatDouble' 'void (float)'
88+
FloatDouble(H);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'FloatDouble' 'void (float)'
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FloatDouble(F);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(double)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (double)' lvalue Function {{.*}} 'FloatDouble' 'void (double)'
98+
FloatDouble(D);
99+
}
100+
101+
// Case 3: A function declared with half and double overloads
102+
// (a) When called with half, it will resolve to half because it is an exact
103+
// match.
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// (b) When called with flaot, it will resolve to double because double is a
105+
// valid promotion.
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// (c) When called with double, it will resolve to double because it is an
107+
// exact match.
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// CHECK: FunctionDecl {{.*}} Case3 'void (half, float, double)'
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void Case3(half H, float F, double D) {
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(half)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (half)' lvalue Function {{.*}} 'HalfDouble' 'void (half)'
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HalfDouble(H);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(double)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (double)' lvalue Function {{.*}} 'HalfDouble' 'void (double)'
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HalfDouble(F);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(double)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (double)' lvalue Function {{.*}} 'HalfDouble' 'void (double)'
124+
HalfDouble(D);
125+
}
126+
127+
// Case 4: A function declared with half and float overloads.
128+
// (a) When called with half, it will resolve to half because half is an exact
129+
// match.
130+
// (b) When called with float it will resolve to float because float is an
131+
// exact match.
132+
// (c) When called with double it will resolve to float because it is the
133+
// float is higher rank than half.
134+
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// CHECK: FunctionDecl {{.*}} Case4 'void (half, float, double)'
136+
void Case4(half H, float F, double D) {
137+
// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(half)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (half)' lvalue Function {{.*}} 'HalfFloat' 'void (half)'
140+
HalfFloat(H);
141+
142+
// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'HalfFloat' 'void (float)'
145+
HalfFloat(F);
146+
147+
// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'HalfFloat' 'void (float)'
150+
HalfFloat(D); // expected-warning{{implicit conversion loses floating-point precision: 'double' to 'float'}}
151+
}
152+
153+
// Case 5: A function declared with only a double overload.
154+
// (a) When called with half, it will resolve to double because double is a
155+
// valid promotion.
156+
// (b) When called with float it will resolve to double because double is a
157+
// valid promotion.
158+
// (c) When called with double it will resolve to double because it is an
159+
// exact match.
160+
161+
// CHECK: FunctionDecl {{.*}} Case5 'void (half, float, double)'
162+
void Case5(half H, float F, double D) {
163+
// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(double)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (double)' lvalue Function {{.*}} 'Double' 'void (double)'
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Double(H);
167+
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(double)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (double)' lvalue Function {{.*}} 'Double' 'void (double)'
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Double(F);
172+
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(double)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (double)' lvalue Function {{.*}} 'Double' 'void (double)'
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Double(D);
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}
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// Case 6: A function declared with only a float overload.
180+
// (a) When called with half, it will resolve to float because float is a
181+
// valid promotion.
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// (b) When called with float it will resolve to float because float is an
183+
// exact match.
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// (c) When called with double it will resolve to float because it is a
185+
// valid conversion.
186+
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// CHECK: FunctionDecl {{.*}} Case6 'void (half, float, double)'
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void Case6(half H, float F, double D) {
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'Float' 'void (float)'
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Float(H);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'Float' 'void (float)'
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Float(F);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(float)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (float)' lvalue Function {{.*}} 'Float' 'void (float)'
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Float(D); // expected-warning{{implicit conversion loses floating-point precision: 'double' to 'float'}}
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}
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// Case 7: A function declared with only a half overload.
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// (a) When called with half, it will resolve to half because half is an
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// exact match
208+
// (b) When called with float it will resolve to half because half is a
209+
// valid conversion.
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// (c) When called with double it will resolve to float because it is a
211+
// valid conversion.
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// CHECK: FunctionDecl {{.*}} Case7 'void (half, float, double)'
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void Case7(half H, float F, double D) {
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(half)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (half)' lvalue Function {{.*}} 'Half' 'void (half)'
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Half(H);
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(half)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (half)' lvalue Function {{.*}} 'Half' 'void (half)'
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Half(F); // expected-warning{{implicit conversion loses floating-point precision: 'float' to 'half'}}
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// CHECK: CallExpr {{.*}} 'void'
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// CHECK-NEXT: ImplicitCastExpr {{.*}} 'void (*)(half)' <FunctionToPointerDecay>
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// CHECK-NEXT: DeclRefExpr {{.*}} 'void (half)' lvalue Function {{.*}} 'Half' 'void (half)'
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Half(D); // expected-warning{{implicit conversion loses floating-point precision: 'double' to 'half'}}
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}

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