The hardware will only forward EXEC_LO; the high 32 bits will be zero.
Additionally, inline constants do not work. At least,
v_addc_u32_e64 v0, vcc, v0, v1, -1
which could conceivably be used to combine (v0 + v1 + 1) into a single
instruction, acts as if all carry-in bits are zero.
The llvm.amdgcn.ps.live test is adjusted; it would be nice to combine
s_mov_b64 s[0:1], exec
v_cndmask_b32_e64 v0, v1, v2, s[0:1]
into
v_mov_b32 v0, v3
but it's not particularly high priority.
Fixes dEQP-GLES31.functional.shaders.helper_invocation.value.*
llvm-svn: 314522
Summary:
This intrinsic returns true if the current thread belongs to a live pixel
and false if it belongs to a pixel that we are executing only for derivative
computation. It will be used by Mesa to implement gl_HelperInvocation.
Note that for pixels that are killed during the shader, this implementation
also returns true, but it doesn't matter because those pixels are always
disabled in the EXEC mask.
This unearthed a corner case in the instruction verifier, which complained
about a v_cndmask 0, 1, exec, exec<imp-use> instruction. That's stupid but
correct code, so make the verifier accept it as such.
Reviewers: arsenm, tstellarAMD
Subscribers: arsenm, llvm-commits
Differential Revision: http://reviews.llvm.org/D19191
llvm-svn: 267102
Nicolai Haehnle