From 893316014a3dc680226869196dc6bd0a7362c079 Mon Sep 17 00:00:00 2001
From: Antonio Maiorano <amaiorano@google.com>
Date: Mon, 21 Nov 2022 15:29:54 +0000
Subject: [PATCH] tint: emit an error for float conversions that are not
 representable

For example, a large f32 value converted to f16 now fails, instead of
resulting in +/-inf.

Bug: tint:1581
Bug: tint:1747
Change-Id: I30fd8c61ecc328206e8f73b626af8046dad4b0b9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/110723
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
---
 src/tint/resolver/const_eval.cc               | 10 +++---
 .../resolver/const_eval_conversion_test.cc    | 33 ++-----------------
 2 files changed, 7 insertions(+), 36 deletions(-)

diff --git a/src/tint/resolver/const_eval.cc b/src/tint/resolver/const_eval.cc
index daa66e5ede..713ad36d3e 100644
--- a/src/tint/resolver/const_eval.cc
+++ b/src/tint/resolver/const_eval.cc
@@ -310,12 +310,10 @@ struct Element : ImplConstant {
             } else if constexpr (IsFloatingPoint<TO>) {
                 // [x -> floating-point] - number not exactly representable
                 // https://www.w3.org/TR/WGSL/#floating-point-conversion
-                switch (conv.Failure()) {
-                    case ConversionFailure::kExceedsNegativeLimit:
-                        return builder.create<Element<TO>>(target_ty, -TO::Inf());
-                    case ConversionFailure::kExceedsPositiveLimit:
-                        return builder.create<Element<TO>>(target_ty, TO::Inf());
-                }
+                builder.Diagnostics().add_error(
+                    tint::diag::System::Resolver,
+                    OverflowErrorMessage(value, builder.FriendlyName(target_ty)), source);
+                return utils::Failure;
             } else if constexpr (IsFloatingPoint<FROM>) {
                 // [floating-point -> integer] - number not exactly representable
                 // https://www.w3.org/TR/WGSL/#floating-point-conversion
diff --git a/src/tint/resolver/const_eval_conversion_test.cc b/src/tint/resolver/const_eval_conversion_test.cc
index 7e6a6fc1a1..ed68725ac2 100644
--- a/src/tint/resolver/const_eval_conversion_test.cc
+++ b/src/tint/resolver/const_eval_conversion_test.cc
@@ -440,38 +440,11 @@ TEST_F(ResolverConstEvalTest, Vec3_Convert_Large_f32_to_u32) {
 TEST_F(ResolverConstEvalTest, Vec3_Convert_Large_f32_to_f16) {
     Enable(ast::Extension::kF16);
 
-    auto* expr = vec3<f16>(vec3<f32>(1e10_f, -1e20_f, 1e30_f));
+    auto* expr = vec3<f16>(Source{{12, 34}}, vec3<f32>(1e10_f, 0_f, 0_f));
     WrapInFunction(expr);
 
-    EXPECT_TRUE(r()->Resolve()) << r()->error();
-
-    constexpr auto kInfinity = std::numeric_limits<double>::infinity();
-
-    auto* sem = Sem().Get(expr);
-    ASSERT_NE(sem, nullptr);
-    auto* vec = sem->Type()->As<sem::Vector>();
-    ASSERT_NE(vec, nullptr);
-    EXPECT_TRUE(vec->type()->Is<sem::F16>());
-    EXPECT_EQ(vec->Width(), 3u);
-    EXPECT_TYPE(sem->ConstantValue()->Type(), sem->Type());
-    EXPECT_FALSE(sem->ConstantValue()->AllEqual());
-    EXPECT_FALSE(sem->ConstantValue()->AnyZero());
-    EXPECT_FALSE(sem->ConstantValue()->AllZero());
-
-    EXPECT_TRUE(sem->ConstantValue()->Index(0)->AllEqual());
-    EXPECT_FALSE(sem->ConstantValue()->Index(0)->AnyZero());
-    EXPECT_FALSE(sem->ConstantValue()->Index(0)->AllZero());
-    EXPECT_EQ(sem->ConstantValue()->Index(0)->As<AFloat>(), kInfinity);
-
-    EXPECT_TRUE(sem->ConstantValue()->Index(1)->AllEqual());
-    EXPECT_FALSE(sem->ConstantValue()->Index(1)->AnyZero());
-    EXPECT_FALSE(sem->ConstantValue()->Index(1)->AllZero());
-    EXPECT_EQ(sem->ConstantValue()->Index(1)->As<AFloat>(), -kInfinity);
-
-    EXPECT_TRUE(sem->ConstantValue()->Index(2)->AllEqual());
-    EXPECT_FALSE(sem->ConstantValue()->Index(2)->AnyZero());
-    EXPECT_FALSE(sem->ConstantValue()->Index(2)->AllZero());
-    EXPECT_EQ(sem->ConstantValue()->Index(2)->As<AFloat>(), kInfinity);
+    EXPECT_FALSE(r()->Resolve());
+    EXPECT_EQ(r()->error(), "12:34 error: value 10000000000 cannot be represented as 'f16'");
 }
 
 TEST_F(ResolverConstEvalTest, Vec3_Convert_Small_f32_to_f16) {