agx: fix ctz of zero with address calcs

../src/asahi/compiler/agx_nir_lower_address.c:82:30: runtime error: passing zero to ctz(), which is not a valid argument
    #0 0x56175dca5684 in pass ../src/asahi/compiler/agx_nir_lower_address.c:82
    waydroid#1 0x56175dca2eda in nir_function_intrinsics_pass ../src/compiler/nir/nir_builder.h:164
    waydroid#2 0x56175dca308c in nir_shader_intrinsics_pass ../src/compiler/nir/nir_builder.h:191
    waydroid#3 0x56175dca68ae in agx_nir_lower_address ../src/asahi/compiler/agx_nir_lower_address.c:167
    waydroid#4 0x56175dc885c0 in agx_optimize_nir ../src/asahi/compiler/agx_compile.c:3063
    waydroid#5 0x56175dc9650d in agx_compile_shader_nir ../src/asahi/compiler/agx_compile.c:3827
    waydroid#6 0x56175dc52148 in main ../src/asahi/clc/asahi_clc.c:359
    waydroid#7 0x7fdf1c343249 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    waydroid#8 0x7fdf1c343304 in __libc_start_main_impl ../csu/libc-start.c:360
    waydroid#9 0x56175dc44760 in _start (/builds/mesa/mesa/_build/src/asahi/clc/asahi_clc+0xbd0760)

Signed-off-by: Alyssa Rosenzweig <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33685>

Author: alyssarosenzweig

src/asahi/compiler/agx_nir_algebraic.py

@@ -215,6 +215,9 @@ def isubshl(x, y, s):
    # neither multiplication overflows.
    (('amul', ('ishl', ('u2u64', 'a@32'), '#b(is_ult_32)'), '#c'),
     ('amul', ('u2u64', a), ('ishl', c, b))),
+
+   # We depending on simplifying this.
+   (('iadd', a, 0), a),
 ]
 
 fuse_lea = []

src/asahi/compiler/agx_nir_lower_address.c

@@ -79,6 +79,8 @@ pass(struct nir_builder *b, nir_intrinsic_instr *intr, void *data)
              * shift.
              */
             int64_t raw_scalar = nir_scalar_as_uint(const_scalar);
+            assert(raw_scalar != 0 && "must have been optimized out");
+
             uint32_t shift = MIN2(__builtin_ctz(raw_scalar), max_shift);
             int64_t k = raw_scalar >> shift;