From b39e6f33b60ef9bbaf81f320aaca6a440d8a6a8f Mon Sep 17 00:00:00 2001 From: Eric Anholt Date: Wed, 22 Sep 2010 11:47:03 -0700 Subject: glsl: Rework assignments with write_masks to have LHS chan count match RHS. It turns out that most people new to this IR are surprised when an assignment to (say) 3 components on the LHS takes 4 components on the RHS. It also makes for quite strange IR output: (assign (constant bool (1)) (x) (var_ref color) (swiz x (var_ref v) )) (assign (constant bool (1)) (y) (var_ref color) (swiz yy (var_ref v) )) (assign (constant bool (1)) (z) (var_ref color) (swiz zzz (var_ref v) )) But even worse, even we get it wrong, as shown by this line of our current step(float, vec4): (assign (constant bool (1)) (w) (var_ref t) (expression float b2f (expression bool >= (swiz w (var_ref x))(var_ref edge)))) where we try to assign a float to the writemasked-out x channel and don't supply anything for the actual w channel we're writing. Drivers right now just get lucky since ir_to_mesa spams the float value across all the source channels of a vec4. Instead, the RHS will now have a number of components equal to the number of components actually being written. Hopefully this confuses everyone less, and it also makes codegen for a scalar target simpler. Reviewed-by: Kenneth Graunke Reviewed-by: Ian Romanick --- src/mesa/program/ir_to_mesa.cpp | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) (limited to 'src/mesa/program') diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp index f24dce79f6..de0cb1ac5b 100644 --- a/src/mesa/program/ir_to_mesa.cpp +++ b/src/mesa/program/ir_to_mesa.cpp @@ -1577,13 +1577,39 @@ ir_to_mesa_visitor::visit(ir_assignment *ir) assert(!ir->lhs->type->is_scalar() && !ir->lhs->type->is_vector()); l.writemask = WRITEMASK_XYZW; } else if (ir->lhs->type->is_scalar()) { - /* FINISHME: This hack makes writing to gl_FragData, which lives in the + /* FINISHME: This hack makes writing to gl_FragDepth, which lives in the * FINISHME: W component of fragment shader output zero, work correctly. */ l.writemask = WRITEMASK_XYZW; } else { + int swizzles[4]; + int first_enabled_chan = 0; + int rhs_chan = 0; + assert(ir->lhs->type->is_vector()); l.writemask = ir->write_mask; + + for (int i = 0; i < 4; i++) { + if (l.writemask & (1 << i)) { + first_enabled_chan = GET_SWZ(r.swizzle, i); + break; + } + } + + /* Swizzle a small RHS vector into the channels being written. + * + * glsl ir treats write_mask as dictating how many channels are + * present on the RHS while Mesa IR treats write_mask as just + * showing which channels of the vec4 RHS get written. + */ + for (int i = 0; i < 4; i++) { + if (l.writemask & (1 << i)) + swizzles[i] = GET_SWZ(r.swizzle, rhs_chan++); + else + swizzles[i] = first_enabled_chan; + } + r.swizzle = MAKE_SWIZZLE4(swizzles[0], swizzles[1], + swizzles[2], swizzles[3]); } assert(l.file != PROGRAM_UNDEFINED); -- cgit v1.2.3