commit 7f301812cb31acec219f155d96895c559053ae85
author Nicolas Capens <capn@google.com> Mon Oct 02 17:32:34 2017 -0400
committer Nicolas Capens <nicolascapens@google.com> Mon Oct 02 21:50:10 2017 +0000
tree 319000eca94050242f0031bf4081c722cae54e41
parent 75b9c1c87b02e169ad4aaa4dd25a7c5f97a7d036

Fix emulation of Short to Byte saturation.

We weren't clamping the value when less than zero.

Bug b/37496082

Change-Id: I3170d14a622f8571f0142dd4ce80f96617c7e0aa
Reviewed-on: https://swiftshader-review.googlesource.com/12948
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Casey Dahlin <sadmac@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Reactor/SubzeroReactor.cpp

diff --git a/src/Reactor/SubzeroReactor.cpp b/src/Reactor/SubzeroReactor.cpp
index b488bf9..a50677f 100644
--- a/src/Reactor/SubzeroReactor.cpp
+++ b/src/Reactor/SubzeroReactor.cpp
@@ -2718,7 +2718,7 @@
 
 	RValue<Byte> SaturateUnsigned(RValue<Short> x)
 	{
-		return Byte(IfThenElse(Int(x) > 0xFF, Int(0xFF), Int(x)));
+		return Byte(IfThenElse(Int(x) > 0xFF, Int(0xFF), IfThenElse(Int(x) < 0, Int(0), Int(x))));
 	}
 
 	RValue<Byte8> AddSat(RValue<Byte8> x, RValue<Byte8> y)
@@ -3977,7 +3977,7 @@
 		return RValue<UShort4>(V(result));
 	}
 
-	RValue<UShort> SaturateUShort(RValue<Int> x)
+	RValue<UShort> SaturateUnsigned(RValue<Int> x)
 	{
 		return UShort(IfThenElse(x > 0xFFFF, Int(0xFFFF), IfThenElse(x < 0, Int(0), x)));
 	}
@@ -3987,10 +3987,10 @@
 		if(emulateIntrinsics)
 		{
 			UShort4 result;
-			result = Insert(result, SaturateUShort(Int(Extract(x, 0)) + Int(Extract(y, 0))), 0);
-			result = Insert(result, SaturateUShort(Int(Extract(x, 1)) + Int(Extract(y, 1))), 1);
-			result = Insert(result, SaturateUShort(Int(Extract(x, 2)) + Int(Extract(y, 2))), 2);
-			result = Insert(result, SaturateUShort(Int(Extract(x, 3)) + Int(Extract(y, 3))), 3);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 0)) + Int(Extract(y, 0))), 0);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 1)) + Int(Extract(y, 1))), 1);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 2)) + Int(Extract(y, 2))), 2);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 3)) + Int(Extract(y, 3))), 3);
 
 			return result;
 		}
@@ -4013,10 +4013,10 @@
 		if(emulateIntrinsics)
 		{
 			UShort4 result;
-			result = Insert(result, SaturateUShort(Int(Extract(x, 0)) - Int(Extract(y, 0))), 0);
-			result = Insert(result, SaturateUShort(Int(Extract(x, 1)) - Int(Extract(y, 1))), 1);
-			result = Insert(result, SaturateUShort(Int(Extract(x, 2)) - Int(Extract(y, 2))), 2);
-			result = Insert(result, SaturateUShort(Int(Extract(x, 3)) - Int(Extract(y, 3))), 3);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 0)) - Int(Extract(y, 0))), 0);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 1)) - Int(Extract(y, 1))), 1);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 2)) - Int(Extract(y, 2))), 2);
+			result = Insert(result, SaturateUnsigned(Int(Extract(x, 3)) - Int(Extract(y, 3))), 3);
 
 			return result;
 		}