From 273b8cd1ca286e2f43b4a464a391fdcaac49f077 Mon Sep 17 00:00:00 2001 From: Ian Romanick Date: Tue, 11 Feb 2020 12:00:00 -0800 Subject: [PATCH] intel/fs: Correctly handle multiply of fsign with a source modifier The other source of the multiply will be interpreted as a uint32_t in an XOR instruction. Any source modifiers with either not be interpreted at all or will be misinterpreted due to the differing types. If the other operand of the multiplication has a source modifier, just emit an extra move to resolve the source modifiers. The negation source modifier problem is difficult to reproduce due to an algebraic optimization that changes (-a*b) to -(a*b). However, changes in MR !1359 push the negations back down. On Gen7+ it might be possible to do slightly better for an abs() source modifier by using BFI2 as a glorified copysign(). On Gen8+ it might be possible to do slightly better for a neg() source modifier by emitting (~a ^ b). There were no shader-db changes on any Intel platform, so I think we can deal with that problem when it arises. See also piglit!224. Fixes: 06d2c116415 ("intel/fs: Add a scale factor to emit_fsign") Reviewed-by: Matt Turner Tested-by: Marge Bot Part-of: --- src/intel/compiler/brw_fs_nir.cpp | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp index 3b34c407f51..1c07f6fed0f 100644 --- a/src/intel/compiler/brw_fs_nir.cpp +++ b/src/intel/compiler/brw_fs_nir.cpp @@ -881,6 +881,16 @@ fs_visitor::emit_fsign(const fs_builder &bld, const nir_alu_instr *instr, } op[0] = offset(op[0], bld, fsign_instr->src[0].swizzle[channel]); + + /* Resolve any source modifiers. We could do slightly better on Gen8+ + * if the only source modifier is negation, but *shrug*. + */ + if (op[1].negate || op[1].abs) { + fs_reg tmp = bld.vgrf(op[1].type); + + bld.MOV(tmp, op[1]); + op[1] = tmp; + } } else { assert(!instr->dest.saturate); } -- 2.30.2