writer/msl: Implement interpolate attributes

Bug: tint:746
Change-Id: Ia96da94b948c0e2c6d99452d5e152113e2af1264
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56245
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/writer/msl/generator_impl.cc

@@ -1142,6 +1142,37 @@ std::string GeneratorImpl::builtin_to_attribute(ast::Builtin builtin) const {
   return "";
 }
 
+std::string GeneratorImpl::interpolation_to_attribute(
+    ast::InterpolationType type,
+    ast::InterpolationSampling sampling) const {
+  std::string attr;
+  switch (sampling) {
+    case ast::InterpolationSampling::kCenter:
+      attr = "center_";
+      break;
+    case ast::InterpolationSampling::kCentroid:
+      attr = "centroid_";
+      break;
+    case ast::InterpolationSampling::kSample:
+      attr = "sample_";
+      break;
+    case ast::InterpolationSampling::kNone:
+      break;
+  }
+  switch (type) {
+    case ast::InterpolationType::kPerspective:
+      attr += "perspective";
+      break;
+    case ast::InterpolationType::kLinear:
+      attr += "no_perspective";
+      break;
+    case ast::InterpolationType::kFlat:
+      attr += "flat";
+      break;
+  }
+  return attr;
+}
+
 bool GeneratorImpl::EmitEntryPointFunction(ast::Function* func) {
   auto* func_sem = program_->Sem().Get(func);
 
@@ -1784,8 +1815,15 @@ bool GeneratorImpl::EmitStructType(const sem::Struct* str) {
           TINT_ICE(Writer, diagnostics_)
               << "invalid use of location decoration";
         }
-      } else if (deco->Is<ast::InterpolateDecoration>()) {
-        TINT_UNIMPLEMENTED(Writer, diagnostics_) << "interpolate decoration";
+      } else if (auto* interpolate = deco->As<ast::InterpolateDecoration>()) {
+        auto attr = interpolation_to_attribute(interpolate->type(),
+                                               interpolate->sampling());
+        if (attr.empty()) {
+          diagnostics_.add_error(diag::System::Writer,
+                                 "unknown interpolation attribute");
+          return false;
+        }
+        out << " [[" << attr << "]]";
       }
     }
 

src/writer/msl/generator_impl.h

@@ -25,6 +25,7 @@
 #include "src/ast/continue_statement.h"
 #include "src/ast/discard_statement.h"
 #include "src/ast/if_statement.h"
+#include "src/ast/interpolate_decoration.h"
 #include "src/ast/loop_statement.h"
 #include "src/ast/member_accessor_expression.h"
 #include "src/ast/return_statement.h"
@@ -253,6 +254,14 @@ class GeneratorImpl : public TextGenerator {
   /// @returns the string name of the builtin or blank on error
   std::string builtin_to_attribute(ast::Builtin builtin) const;
 
+  /// Converts interpolation attributes to an MSL attribute
+  /// @param type the interpolation type
+  /// @param sampling the interpolation sampling
+  /// @returns the string name of the attribute or blank on error
+  std::string interpolation_to_attribute(
+      ast::InterpolationType type,
+      ast::InterpolationSampling sampling) const;
+
  private:
   /// @returns the resolved type of the ast::Expression `expr`
   /// @param expr the expression

test/shader_io/interpolate_input_parameters.wgsl.expected.msl

@@ -1,10 +1,26 @@
-SKIP: FAILED
+#include <metal_stdlib>
 
-../../src/writer/msl/generator_impl.cc:1782 internal compiler error: TINT_UNIMPLEMENTED interpolate decoration
-********************************************************************
-*  The tint shader compiler has encountered an unexpected error.   *
-*                                                                  *
-*  Please help us fix this issue by submitting a bug report at     *
-*  crbug.com/tint with the source program that triggered the bug.  *
-********************************************************************
+using namespace metal;
+struct tint_symbol_2 {
+  float none [[user(locn0)]];
+  float flat [[user(locn1)]] [[flat]];
+  float perspective_center [[user(locn2)]] [[center_perspective]];
+  float perspective_centroid [[user(locn3)]] [[centroid_perspective]];
+  float perspective_sample [[user(locn4)]] [[sample_perspective]];
+  float linear_center [[user(locn5)]] [[center_no_perspective]];
+  float linear_centroid [[user(locn6)]] [[centroid_no_perspective]];
+  float linear_sample [[user(locn7)]] [[sample_no_perspective]];
+};
+
+fragment void tint_symbol(tint_symbol_2 tint_symbol_1 [[stage_in]]) {
+  float const none = tint_symbol_1.none;
+  float const flat = tint_symbol_1.flat;
+  float const perspective_center = tint_symbol_1.perspective_center;
+  float const perspective_centroid = tint_symbol_1.perspective_centroid;
+  float const perspective_sample = tint_symbol_1.perspective_sample;
+  float const linear_center = tint_symbol_1.linear_center;
+  float const linear_centroid = tint_symbol_1.linear_centroid;
+  float const linear_sample = tint_symbol_1.linear_sample;
+  return;
+}
 

test/shader_io/interpolate_input_struct.wgsl.expected.msl

@@ -1,10 +1,29 @@
-SKIP: FAILED
+#include <metal_stdlib>
 
-../../src/writer/msl/generator_impl.cc:1782 internal compiler error: TINT_UNIMPLEMENTED interpolate decoration
-********************************************************************
-*  The tint shader compiler has encountered an unexpected error.   *
-*                                                                  *
-*  Please help us fix this issue by submitting a bug report at     *
-*  crbug.com/tint with the source program that triggered the bug.  *
-********************************************************************
+using namespace metal;
+struct In {
+  float none;
+  float flat;
+  float perspective_center;
+  float perspective_centroid;
+  float perspective_sample;
+  float linear_center;
+  float linear_centroid;
+  float linear_sample;
+};
+struct tint_symbol_2 {
+  float none [[user(locn0)]];
+  float flat [[user(locn1)]] [[flat]];
+  float perspective_center [[user(locn2)]] [[center_perspective]];
+  float perspective_centroid [[user(locn3)]] [[centroid_perspective]];
+  float perspective_sample [[user(locn4)]] [[sample_perspective]];
+  float linear_center [[user(locn5)]] [[center_no_perspective]];
+  float linear_centroid [[user(locn6)]] [[centroid_no_perspective]];
+  float linear_sample [[user(locn7)]] [[sample_no_perspective]];
+};
+
+fragment void tint_symbol(tint_symbol_2 tint_symbol_1 [[stage_in]]) {
+  In const in = {.none=tint_symbol_1.none, .flat=tint_symbol_1.flat, .perspective_center=tint_symbol_1.perspective_center, .perspective_centroid=tint_symbol_1.perspective_centroid, .perspective_sample=tint_symbol_1.perspective_sample, .linear_center=tint_symbol_1.linear_center, .linear_centroid=tint_symbol_1.linear_centroid, .linear_sample=tint_symbol_1.linear_sample};
+  return;
+}
 

test/shader_io/interpolate_return_struct.wgsl.expected.msl

@@ -1,10 +1,32 @@
-SKIP: FAILED
+#include <metal_stdlib>
 
-../../src/writer/msl/generator_impl.cc:1782 internal compiler error: TINT_UNIMPLEMENTED interpolate decoration
-********************************************************************
-*  The tint shader compiler has encountered an unexpected error.   *
-*                                                                  *
-*  Please help us fix this issue by submitting a bug report at     *
-*  crbug.com/tint with the source program that triggered the bug.  *
-********************************************************************
+using namespace metal;
+struct Out {
+  float4 pos;
+  float none;
+  float flat;
+  float perspective_center;
+  float perspective_centroid;
+  float perspective_sample;
+  float linear_center;
+  float linear_centroid;
+  float linear_sample;
+};
+struct tint_symbol_1 {
+  float none [[user(locn0)]];
+  float flat [[user(locn1)]] [[flat]];
+  float perspective_center [[user(locn2)]] [[center_perspective]];
+  float perspective_centroid [[user(locn3)]] [[centroid_perspective]];
+  float perspective_sample [[user(locn4)]] [[sample_perspective]];
+  float linear_center [[user(locn5)]] [[center_no_perspective]];
+  float linear_centroid [[user(locn6)]] [[centroid_no_perspective]];
+  float linear_sample [[user(locn7)]] [[sample_no_perspective]];
+  float4 pos [[position]];
+};
+
+vertex tint_symbol_1 tint_symbol() {
+  Out const tint_symbol_2 = {};
+  tint_symbol_1 const tint_symbol_3 = {.none=tint_symbol_2.none, .flat=tint_symbol_2.flat, .perspective_center=tint_symbol_2.perspective_center, .perspective_centroid=tint_symbol_2.perspective_centroid, .perspective_sample=tint_symbol_2.perspective_sample, .linear_center=tint_symbol_2.linear_center, .linear_centroid=tint_symbol_2.linear_centroid, .linear_sample=tint_symbol_2.linear_sample, .pos=tint_symbol_2.pos};
+  return tint_symbol_3;
+}