Fix horizontal max/min for uchar

Fixes: #349
VcDevel · Sep 29, 2023 · dec4980 · dec4980
1 parent ea663e2
commit dec4980
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Showing 2 changed files with 20 additions and 3 deletions.
diff --git a/Vc/sse/detail.h b/Vc/sse/detail.h
@@ -764,9 +764,9 @@ Vc_INTRINSIC  schar max(__m128i a,  schar) {
     return std::max(schar(_mm_cvtsi128_si32(a) >> 8), schar(_mm_cvtsi128_si32(a)));
 }
 Vc_INTRINSIC  uchar max(__m128i a,  uchar) {
-    a = max(a, _mm_shuffle_epi32(a, _MM_SHUFFLE(1, 0, 3, 2)), schar());
-    a = max(a, _mm_shufflelo_epi16(a, _MM_SHUFFLE(1, 0, 3, 2)), schar());
-    a = max(a, _mm_shufflelo_epi16(a, _MM_SHUFFLE(1, 1, 1, 1)), schar());
+    a = max(a, _mm_shuffle_epi32(a, _MM_SHUFFLE(1, 0, 3, 2)), uchar());
+    a = max(a, _mm_shufflelo_epi16(a, _MM_SHUFFLE(1, 0, 3, 2)), uchar());
+    a = max(a, _mm_shufflelo_epi16(a, _MM_SHUFFLE(1, 1, 1, 1)), uchar());
     return std::max((_mm_cvtsi128_si32(a) >> 8) & 0xff, _mm_cvtsi128_si32(a) & 0xff);
 }
 

diff --git a/tests/arithmetics.cpp b/tests/arithmetics.cpp
@@ -472,6 +472,23 @@ TEST_TYPES(Vec, testMax, AllVectors)
     }
 }
 
+#ifdef Vc_IMPL_AVX2
+TEST(minChar)
+{
+    uint8_t a[64]{0, 10, 250};
+    COMPARE(Vc::schar_v(reinterpret_cast<Vc::schar*>(a)).min(), Vc::schar{-6});
+    COMPARE(Vc::uchar_v(a).min(), Vc::uchar{0});
+}
+
+// Tests issue: https://github.com/VcDevel/Vc/issues/349
+TEST(maxChar)
+{
+    uint8_t a[64]{0, 10, 250};
+    COMPARE(Vc::schar_v(reinterpret_cast<Vc::schar*>(a)).max(), Vc::schar{10});
+    COMPARE(Vc::uchar_v(a).max(), Vc::uchar{250});
+}
+#endif
+
 // testProduct{{{1
 TEST_TYPES(Vec, testProduct, AllVectors)
 {