Honor lowp/mediump/highp precision qualifiers in IRGenerator.

This CL does not update the DSLParser to honor these precision
qualifiers; that will be done in a followup.

Change-Id: Ib629bc99c0e6c7afb550a381d4e3b6ccc26aa64e
Bug: skia:12248
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436337
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

gn/sksl_tests.gni

@@ -57,6 +57,7 @@ sksl_error_tests = [
   "/sksl/errors/ForTypeMismatch.sksl",
   "/sksl/errors/FunctionParameterOfVoid.sksl",
   "/sksl/errors/GenericArgumentMismatch.sksl",
+  "/sksl/errors/PrecisionQualifiersDisallowed.sksl",
   "/sksl/errors/IfTypeMismatch.sksl",
   "/sksl/errors/InVarWithInitializerExpression.sksl",
   "/sksl/errors/InterfaceBlockScope.sksl",
@@ -533,6 +534,7 @@ sksl_rte_error_tests = [
   "/sksl/runtime_errors/IllegalArrayOps.rts",
   "/sksl/runtime_errors/IllegalIndexing.rts",
   "/sksl/runtime_errors/IllegalOperators.rts",
+  "/sksl/runtime_errors/IllegalPrecisionQualifiers.rts",
   "/sksl/runtime_errors/IllegalRecursionComplex.rts",
   "/sksl/runtime_errors/IllegalRecursionMutual.rts",
   "/sksl/runtime_errors/IllegalRecursionSimple.rts",

resources/sksl/errors/PrecisionQualifiersDisallowed.sksl

@@ -0,0 +1,4 @@
+// Precision qualifiers are only allowed in a Runtime Effect.
+void h() { highp int x; }
+void m() { mediump int x; }
+void l() { lowp int x; }

resources/sksl/runtime/PrecisionQualifiers.rts

@@ -1,9 +1,61 @@
-uniform half4 colorGreen;
+uniform half4 colorGreen, colorRed;
+
+bool test_scalar() {
+    mediump float mp  = 0.5;
+    highp   float hp  = mp;
+    highp   int   ihp = 2;
+    mediump int   imp = ihp;
+
+    return mp == hp && ihp == imp;
+}
+
+bool test_vector() {
+    mediump vec2 mp2 = vec2(2);
+    highp   vec2 hp2 = mp2;
+    mediump vec3 mp3 = vec3(3);
+    highp   vec3 hp3 = mp3;
+    mediump vec4 mp4 = vec4(4);
+    highp   vec4 hp4 = mp4;
+
+    highp   ivec2 ihp2 = ivec2(2);
+    mediump ivec2 imp2 = ihp2;
+    highp   ivec3 ihp3 = ivec3(3);
+    mediump ivec3 imp3 = ihp3;
+    highp   ivec4 ihp4 = ivec4(4);
+    mediump ivec4 imp4 = ihp4;
+
+    return mp2 == hp2   && hp3 == mp3   && mp4 == hp4 &&
+           imp2 == ihp2 && ihp3 == imp3 && imp4 == ihp4;
+}
+
+bool test_matrix() {
+    mediump mat2 mp2 = mat2(2);
+    highp   mat2 hp2 = mp2;
+    mediump mat3 mp3 = mat3(3);
+    highp   mat3 hp3 = mp3;
+    mediump mat4 mp4 = mat4(4);
+    highp   mat4 hp4 = mp4;
+
+    return mp2 == hp2 && hp3 == mp3 && mp4 == hp4;
+}
+
+bool test_array() {
+    mediump float  mf[1]; mf[0] = 1;
+    highp   float  hf[1]; hf[0] = 1;
+    mediump vec2   mv[2]; mv[0] = vec2(0, 1); mv[1] = vec2(2, 3);
+    highp   vec2   hv[2]; hv[0] = vec2(0, 1); hv[1] = vec2(2, 3);
+
+    return mf[0] == hf[0] && hv[0] == mv[0] && mv[1] == hv[1];
+}
 
 vec4 main(vec2 coords) {
-    highp vec4 zero = vec4(0);
-    mediump vec4 green = colorGreen;
-    lowp vec4 one = vec4(1);
+    highp   vec4 zero = vec4(0);
+    mediump vec4 one = vec4(1);
+    lowp vec4 green = colorGreen;
+    green = green * one + zero;
 
-    return green * one + zero;
+    highp vec4 red = colorRed;
+    red = (red + zero) * one;
+
+    return (test_scalar() && test_vector() && test_matrix() && test_array()) ? green : red;
 }

resources/sksl/runtime_errors/IllegalPrecisionQualifiers.rts

@@ -0,0 +1,14 @@
+// Expect 10 errors
+
+struct S { int i; };
+
+mediump highp int no_multiple_qualifiers;
+mediump lowp int no_multiple_qualifiers_2;
+highp lowp int no_multiple_qualifiers_3;
+highp mediump lowp int no_multiple_qualifiers_4;
+highp S no_structs;
+mediump bool no_bools;
+uniform lowp colorFilter no_opaque;
+uniform highp half no_half_highp;
+uniform mediump half no_half_mediump;
+uniform lowp half no_lowp_mediump;

src/sksl/SkSLIRGenerator.cpp

@@ -294,7 +294,8 @@ void IRGenerator::checkVarDeclaration(int offset, const Modifiers& modifiers, co
                                         "float3, or float4 variables");
         }
     }
-    int permitted = Modifiers::kConst_Flag;
+    int permitted = Modifiers::kConst_Flag | Modifiers::kHighp_Flag | Modifiers::kMediump_Flag |
+                    Modifiers::kLowp_Flag;
     if (storage == Variable::Storage::kGlobal) {
         permitted |= Modifiers::kIn_Flag | Modifiers::kOut_Flag | Modifiers::kUniform_Flag |
                      Modifiers::kFlat_Flag | Modifiers::kNoPerspective_Flag;
@@ -393,6 +394,11 @@ StatementArray IRGenerator::convertVarDeclarations(const ASTNode& decls,
     if (!baseType) {
         return {};
     }
+    baseType = baseType->applyPrecisionQualifiers(fContext, modifiers, fSymbolTable.get(),
+                                                  decls.fOffset);
+    if (!baseType) {
+        return {};
+    }
 
     this->checkVarDeclaration(decls.fOffset, modifiers, baseType, storage);
 

src/sksl/ir/SkSLType.cpp

@@ -441,6 +441,72 @@ CoercionCost Type::coercionCost(const Type& other) const {
     return CoercionCost::Impossible();
 }
 
+const Type* Type::applyPrecisionQualifiers(const Context& context,
+                                           const Modifiers& modifiers,
+                                           SymbolTable* symbols,
+                                           int offset) const {
+    // SkSL doesn't support low precision, so `lowp` is interpreted as medium precision.
+    bool highp   = modifiers.fFlags & Modifiers::kHighp_Flag;
+    bool mediump = modifiers.fFlags & Modifiers::kMediump_Flag;
+    bool lowp    = modifiers.fFlags & Modifiers::kLowp_Flag;
+
+    if (!lowp && !mediump && !highp) {
+        // No precision qualifiers here. Return the type as-is.
+        return this;
+    }
+
+    if (!ProgramConfig::IsRuntimeEffect(context.fConfig->fKind)) {
+        // We want to discourage precision modifiers internally. Instead, use the type that
+        // corresponds to the precision you need. (e.g. half vs float, short vs int)
+        context.fErrors.error(offset, "precision qualifiers are not allowed");
+        return nullptr;
+    }
+
+    if ((int(lowp) + int(mediump) + int(highp)) != 1) {
+        context.fErrors.error(offset, "only one precision qualifier can be used");
+        return nullptr;
+    }
+
+    const Type& component = this->componentType();
+    if (component.highPrecision()) {
+        if (highp) {
+            // Type is already high precision, and we are requesting high precision. Return as-is.
+            return this;
+        }
+
+        // Ascertain the mediump equivalent type for this type, if any.
+        const Type* mediumpType;
+        switch (component.numberKind()) {
+            case Type::NumberKind::kFloat:
+                mediumpType = context.fTypes.fHalf.get();
+                break;
+
+            case Type::NumberKind::kSigned:
+                mediumpType = context.fTypes.fShort.get();
+                break;
+
+            case Type::NumberKind::kUnsigned:
+                mediumpType = context.fTypes.fUShort.get();
+                break;
+
+            default:
+                mediumpType = nullptr;
+                break;
+        }
+
+        if (mediumpType) {
+            // Convert the mediump component type into the final vector/matrix/array type as needed.
+            return this->isArray()
+                           ? symbols->addArrayDimension(mediumpType, this->columns())
+                           : &mediumpType->toCompound(context, this->columns(), this->rows());
+        }
+    }
+
+    context.fErrors.error(offset, "type '" + this->displayName() +
+                                  "' does not support precision qualifiers");
+    return nullptr;
+}
+
 const Type& Type::toCompound(const Context& context, int columns, int rows) const {
     SkASSERT(this->isScalar());
     if (columns == 1 && rows == 1) {

src/sksl/ir/SkSLType.h

@@ -23,6 +23,7 @@ namespace SkSL {
 
 class BuiltinTypes;
 class Context;
+class SymbolTable;
 
 struct CoercionCost {
     static CoercionCost Free()              { return {    0,    0, false }; }
@@ -510,6 +511,16 @@ public:
      */
     const Type& toCompound(const Context& context, int columns, int rows) const;
 
+    /**
+     * Returns a type which honors the precision qualifiers set in Modifiers. e.g., kMediump_Flag
+     * when applied to `float2` will return `half2`. Generates an error if the precision qualifiers
+     * don't make sense, e.g. `highp bool` or `mediump MyStruct`.
+     */
+    const Type* applyPrecisionQualifiers(const Context& context,
+                                         const Modifiers& modifiers,
+                                         SymbolTable* symbols,
+                                         int offset) const;
+
     /**
      * Coerces the passed-in expression to this type. If the types are incompatible, reports an
      * error and returns null.

tests/sksl/errors/PrecisionQualifiersDisallowed.glsl

@@ -0,0 +1,6 @@
+### Compilation failed:
+
+error: 2: precision qualifiers are not allowed
+error: 3: precision qualifiers are not allowed
+error: 4: precision qualifiers are not allowed
+3 errors

tests/sksl/runtime/PrecisionQualifiers.skvm

@@ -1,6 +1,10 @@
-### Compilation failed:
-
-error: 4: 'highp' is not permitted here
-error: 5: 'mediump' is not permitted here
-error: 6: 'lowp' is not permitted here
-3 errors
+4 registers, 8 instructions:
+0	r0 = uniform32 ptr0 4
+1	r1 = uniform32 ptr0 8
+2	r2 = uniform32 ptr0 C
+3	r3 = uniform32 ptr0 10
+loop:
+4	    store32 ptr1 r0
+5	    store32 ptr2 r1
+6	    store32 ptr3 r2
+7	    store32 ptr4 r3

tests/sksl/runtime/PrecisionQualifiers.stage

@@ -1,6 +1,56 @@
-### Compilation failed:
-
-error: 4: 'highp' is not permitted here
-error: 5: 'mediump' is not permitted here
-error: 6: 'lowp' is not permitted here
-3 errors
+uniform half4 colorGreen;
+uniform half4 colorRed;
+bool test_vector_0()
+{
+	half2 mp2 = half2(2.0);
+	float2 hp2 = float2(mp2);
+	half3 mp3 = half3(3.0);
+	float3 hp3 = float3(mp3);
+	half4 mp4 = half4(4.0);
+	float4 hp4 = float4(mp4);
+	int2 ihp2 = int2(2);
+	short2 imp2 = short2(ihp2);
+	int3 ihp3 = int3(3);
+	short3 imp3 = short3(ihp3);
+	int4 ihp4 = int4(4);
+	short4 imp4 = short4(ihp4);
+	return ((((float2(mp2) == hp2 && hp3 == float3(mp3)) && float4(mp4) == hp4) && int2(imp2) == ihp2) && ihp3 == int3(imp3)) && int4(imp4) == ihp4;
+}
+bool test_matrix_0()
+{
+	half2x2 mp2 = half2x2(2.0);
+	float2x2 hp2 = float2x2(mp2);
+	half3x3 mp3 = half3x3(3.0);
+	float3x3 hp3 = float3x3(mp3);
+	half4x4 mp4 = half4x4(4.0);
+	float4x4 hp4 = float4x4(mp4);
+	return (float2x2(mp2) == hp2 && hp3 == float3x3(mp3)) && float4x4(mp4) == hp4;
+}
+bool test_array_0()
+{
+	half mf[1];
+	mf[0] = 1.0;
+	float hf[1];
+	hf[0] = 1.0;
+	half2 mv[2];
+	mv[0] = half2(0.0, 1.0);
+	mv[1] = half2(2.0, 3.0);
+	float2 hv[2];
+	hv[0] = float2(0.0, 1.0);
+	hv[1] = float2(2.0, 3.0);
+	return (float(mf[0]) == hf[0] && hv[0] == float2(mv[0])) && float2(mv[1]) == hv[1];
+}
+float4 main(float2 coords)
+{
+	float4 zero = float4(0.0);
+	half4 one = half4(1.0);
+	half4 green = colorGreen;
+	green = half4(float4(green * one) + zero);
+	float4 red = float4(colorRed);
+	red = (red + zero) * float4(one);
+	half _0_mp = 0.5;
+	float _1_hp = float(_0_mp);
+	int _2_ihp = 2;
+	short _3_imp = short(_2_ihp);
+	return half4((((float(_0_mp) == _1_hp && _2_ihp == int(_3_imp)) && test_vector_0()) && test_matrix_0()) && test_array_0() ? float4(green) : red);
+}

tests/sksl/runtime_errors/IllegalPrecisionQualifiers.skvm

@@ -0,0 +1,13 @@
+### Compilation failed:
+
+error: 5: only one precision qualifier can be used
+error: 6: only one precision qualifier can be used
+error: 7: only one precision qualifier can be used
+error: 8: only one precision qualifier can be used
+error: 9: type 'S' does not support precision qualifiers
+error: 10: type 'bool' does not support precision qualifiers
+error: 11: type 'colorFilter' does not support precision qualifiers
+error: 12: type 'half' does not support precision qualifiers
+error: 13: type 'half' does not support precision qualifiers
+error: 14: type 'half' does not support precision qualifiers
+10 errors