tint/sem: Consider sign bit for Constant helpers.

Constant::AnyZero(), Constant::AllZero() now consider -0.0 as non-zero,
as this is different from WGSL's zero-initializer value for floating
point numbers.

Also consider FP sign for Constant::AllEqual().

Bug: tint:1504
Change-Id: I00503880ee29bd741b94cc98909a8a823e32522a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/92243
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>

src/tint/sem/constant.cc

@@ -14,6 +14,7 @@
 
 #include "src/tint/sem/constant.h"
 
+#include <cmath>
 #include <utility>
 
 #include "src/tint/debug.h"
@@ -26,6 +27,17 @@ namespace {
 size_t CountElements(const Constant::Elements& elements) {
     return std::visit([](auto&& vec) { return vec.size(); }, elements);
 }
+
+template <typename T>
+bool IsNegativeFloat(T value) {
+    (void)value;
+    if constexpr (IsFloatingPoint<T>) {
+        return std::signbit(value);
+    } else {
+        return false;
+    }
+}
+
 }  // namespace
 
 Constant::Constant() {}
@@ -47,7 +59,7 @@ bool Constant::AnyZero() const {
     return WithElements([&](auto&& vec) {
         using T = typename std::decay_t<decltype(vec)>::value_type;
         for (auto el : vec) {
-            if (el == T(0)) {
+            if (el == T(0) && !IsNegativeFloat(el.value)) {
                 return true;
             }
         }
@@ -59,7 +71,7 @@ bool Constant::AllZero() const {
     return WithElements([&](auto&& vec) {
         using T = typename std::decay_t<decltype(vec)>::value_type;
         for (auto el : vec) {
-            if (el != T(0)) {
+            if (el != T(0) || IsNegativeFloat(el.value)) {
                 return false;
             }
         }
@@ -71,8 +83,9 @@ bool Constant::AllEqual(size_t start, size_t end) const {
     return WithElements([&](auto&& vec) {
         if (!vec.empty()) {
             auto value = vec[start];
+            bool float_sign = IsNegativeFloat(vec[start].value);
             for (size_t i = start + 1; i < end; i++) {
-                if (vec[i] != value) {
+                if (vec[i] != value || float_sign != IsNegativeFloat(vec[i].value)) {
                     return false;
                 }
             }

src/tint/sem/constant.h

@@ -129,13 +129,13 @@ class Constant {
     /// @returns the elements as a vector of AFloat
     inline const AFloats& FElements() const { return std::get<AFloats>(elems_); }
 
-    /// @returns true if any element is zero
+    /// @returns true if any element is positive zero
     bool AnyZero() const;
 
-    /// @returns true if all elements are zero
+    /// @returns true if all elements are positive zero
     bool AllZero() const;
 
-    /// @returns true if all elements are the same value
+    /// @returns true if all elements are the same value, with the same sign-bit.
     bool AllEqual() const { return AllEqual(0, ElementCount()); }
 
     /// @param start the first element index

src/tint/sem/constant_test.cc

@@ -202,6 +202,20 @@ TEST_F(ConstantTest, AnyZero) {
     EXPECT_EQ(Constant(vec3_ai, {1_a, 0_a, 3_a}).AnyZero(), true);
     EXPECT_EQ(Constant(vec3_ai, {1_a, 2_a, 0_a}).AnyZero(), true);
     EXPECT_EQ(Constant(vec3_ai, {0_a, 0_a, 0_a}).AnyZero(), true);
+
+    auto* vec3_af = create<Vector>(create<AbstractFloat>(), 3u);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 2._a, 3._a}).AnyZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 2._a, 3._a}).AnyZero(), true);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 0._a, 3._a}).AnyZero(), true);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 2._a, 0._a}).AnyZero(), true);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 0._a, 0._a}).AnyZero(), true);
+
+    EXPECT_EQ(Constant(vec3_af, {1._a, -2._a, 3._a}).AnyZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -2._a, 3._a}).AnyZero(), true);
+    EXPECT_EQ(Constant(vec3_af, {1._a, -0._a, 3._a}).AnyZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, -2._a, 0._a}).AnyZero(), true);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -0._a, 0._a}).AnyZero(), true);
+    EXPECT_EQ(Constant(vec3_af, {-0._a, -0._a, -0._a}).AnyZero(), false);
 }
 
 TEST_F(ConstantTest, AllZero) {
@@ -211,6 +225,20 @@ TEST_F(ConstantTest, AllZero) {
     EXPECT_EQ(Constant(vec3_ai, {1_a, 0_a, 3_a}).AllZero(), false);
     EXPECT_EQ(Constant(vec3_ai, {1_a, 2_a, 0_a}).AllZero(), false);
     EXPECT_EQ(Constant(vec3_ai, {0_a, 0_a, 0_a}).AllZero(), true);
+
+    auto* vec3_af = create<Vector>(create<AbstractFloat>(), 3u);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 2._a, 3._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 2._a, 3._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 0._a, 3._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 2._a, 0._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 0._a, 0._a}).AllZero(), true);
+
+    EXPECT_EQ(Constant(vec3_af, {1._a, -2._a, 3._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -2._a, 3._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, -0._a, 3._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, -2._a, 0._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -0._a, 0._a}).AllZero(), false);
+    EXPECT_EQ(Constant(vec3_af, {-0._a, -0._a, -0._a}).AllZero(), false);
 }
 
 TEST_F(ConstantTest, AllEqual) {
@@ -221,6 +249,17 @@ TEST_F(ConstantTest, AllEqual) {
     EXPECT_EQ(Constant(vec3_ai, {1_a, 1_a, 1_a}).AllEqual(), true);
     EXPECT_EQ(Constant(vec3_ai, {2_a, 2_a, 2_a}).AllEqual(), true);
     EXPECT_EQ(Constant(vec3_ai, {3_a, 3_a, 3_a}).AllEqual(), true);
+    EXPECT_EQ(Constant(vec3_ai, {0_a, 0_a, 0_a}).AllEqual(), true);
+
+    auto* vec3_af = create<Vector>(create<AbstractFloat>(), 3u);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 2._a, 3._a}).AllEqual(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 1._a, 3._a}).AllEqual(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 3._a, 3._a}).AllEqual(), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 1._a, 1._a}).AllEqual(), true);
+    EXPECT_EQ(Constant(vec3_af, {2._a, 2._a, 2._a}).AllEqual(), true);
+    EXPECT_EQ(Constant(vec3_af, {3._a, 3._a, 3._a}).AllEqual(), true);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 0._a, 0._a}).AllEqual(), true);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -0._a, 0._a}).AllEqual(), false);
 }
 
 TEST_F(ConstantTest, AllEqualRange) {
@@ -231,6 +270,28 @@ TEST_F(ConstantTest, AllEqualRange) {
     EXPECT_EQ(Constant(vec3_ai, {1_a, 1_a, 1_a}).AllEqual(1, 3), true);
     EXPECT_EQ(Constant(vec3_ai, {2_a, 2_a, 2_a}).AllEqual(1, 3), true);
     EXPECT_EQ(Constant(vec3_ai, {2_a, 2_a, 3_a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_ai, {1_a, 0_a, 0_a}).AllEqual(1, 3), true);
+    EXPECT_EQ(Constant(vec3_ai, {0_a, 1_a, 0_a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_ai, {0_a, 0_a, 1_a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_ai, {0_a, 0_a, 0_a}).AllEqual(1, 3), true);
+
+    auto* vec3_af = create<Vector>(create<AbstractFloat>(), 3u);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 2._a, 3._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 1._a, 3._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 3._a, 3._a}).AllEqual(1, 3), true);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 1._a, 1._a}).AllEqual(1, 3), true);
+    EXPECT_EQ(Constant(vec3_af, {2._a, 2._a, 2._a}).AllEqual(1, 3), true);
+    EXPECT_EQ(Constant(vec3_af, {2._a, 2._a, 3._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {1._a, 0._a, 0._a}).AllEqual(1, 3), true);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 1._a, 0._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 0._a, 1._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, 0._a, 0._a}).AllEqual(1, 3), true);
+    EXPECT_EQ(Constant(vec3_af, {1._a, -0._a, 0._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -1._a, 0._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -0._a, 1._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -0._a, 0._a}).AllEqual(1, 3), false);
+    EXPECT_EQ(Constant(vec3_af, {0._a, -0._a, -0._a}).AllEqual(1, 3), true);
+    EXPECT_EQ(Constant(vec3_af, {-0._a, -0._a, -0._a}).AllEqual(1, 3), true);
 }
 
 }  // namespace