Reading src_shared_base, src_shared_limit, src_private_base or
src_private_limit (scalar source codes 235-238) refused the shader since
#1940, because their values were unknown. They now read as the 64-bit
apertures that the flat routing from #1190 classifies: a base is the
aperture's high dword over a low dword of 0, a limit is the same high
dword over 0xffffffff (shared 0x80000000, private 0x70000000).
A 64-bit read (s_mov_b64, a 64-bit VALU source, a wave64 lane mask)
gets the whole value and a 32-bit read gets the low dword. A flat
pointer built from the high dword therefore reaches LDS or scratch, and
64-bit compares against the limits order as on the hardware. The flat
routing and the reads share one definition of the two high dwords.
Sources: LLVM SIRegisterInfo.td (aperture registers are 64-bit, their
low 32 bits are always 0 for a base and -1 for a limit) and
getSegmentAperture in AMDGPULegalizerInfo.cpp and SIISelLowering.cpp
(a 64-bit read whose high half is the aperture); the RDNA 2 ISA guide,
sections 5.2, 5.8 (SH_MEM_BASES holds 16-bit bases) and 9.3; the KFD's
MAKE_LDS_APP_LIMIT (limit = base | 0xffffffff); the gfx1030 and gfx1035
readouts on #1190 and #3803. The PS5's two high dwords stay inferred,
as the shader technical debt records.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Reuse the prerequisite call-region analysis for signed relative calls, including callees after s_endpgm. Lower the saved link as shader base plus PC+4 and reject unsupported targets and call shapes.
Add decoder, IR, CFG and Vulkan execution regressions. Seven focused CMake tests pass; five layouts cover 15 dispatches and 3,200 output comparisons on lavapipe. Record ISA sources and native RDNA2/PS5 limits in TechnicalDebt.
s_sethalt with SIMM16[0] clear is a no-op; s_sethalt 1, s_sendmsghalt, a reached s_code_end, s_rfe_b64, the ds_gws_* instructions and ds_ordered_count throw with the reason at translation. Linear decoding stops at s_code_end like at s_endpgm, so code padded with s_code_end after a final backward branch decodes. Encodings from LLVM SOPInstructions.td and DSInstructions.td, checked against the gfx10 MC tests; semantics from the RDNA 2 ISA guide.
The decoder stopped at an s_endpgm unless the next word was a known branch
target. When an earlier branch jumps further than that word, the block right
after the s_endpgm is entered only from later code, so the program was cut
short and the graph builder rejected the branch as targeting an invalid
program counter. Stop only when no decoded branch targets a word at or past
the one after the s_endpgm.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
