From e10b11a5d06de6efd1ccb39a0ed6bb602761df6d Mon Sep 17 00:00:00 2001 From: Yuri Kunde Schlesner Date: Sun, 12 Feb 2017 13:29:14 -0800 Subject: [PATCH] video_core/shader: Document sanitized MUL operation --- src/video_core/shader/shader_jit_x64_compiler.cpp | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/video_core/shader/shader_jit_x64_compiler.cpp b/src/video_core/shader/shader_jit_x64_compiler.cpp index 92b35dbc0..2dbc8b147 100644 --- a/src/video_core/shader/shader_jit_x64_compiler.cpp +++ b/src/video_core/shader/shader_jit_x64_compiler.cpp @@ -295,14 +295,22 @@ void JitShader::Compile_DestEnable(Instruction instr, Xmm src) { } void JitShader::Compile_SanitizedMul(Xmm src1, Xmm src2, Xmm scratch) { + // 0 * inf and inf * 0 in the PICA should return 0 instead of NaN. This can be implemented by + // checking for NaNs before and after the multiplication. If the multiplication result is NaN + // where neither source was, this NaN was generated by a 0 * inf multiplication, and so the + // result should be transformed to 0 to match PICA fp rules. + + // Set scratch to mask of (src1 != NaN and src2 != NaN) movaps(scratch, src1); cmpordps(scratch, src2); mulps(src1, src2); + // Set src2 to mask of (result == NaN) movaps(src2, src1); cmpunordps(src2, src2); + // Clear components where scratch != src2 (i.e. if result is NaN where neither source was NaN) xorps(scratch, src2); andps(src1, scratch); }