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Branches: main Add float registers to the Mercury abstract machine, implemented as an array of MR_Float in the Mercury engine structure. Float registers are only useful if a Mercury `float' is wider than a word (i.e. when using double precision floats on 32-bit platforms) so we let them exist only then. In other cases floats may simply be passed via the regular registers, as before. Currently, higher order calls still require the use of the regular registers for all arguments. As all exported procedures are potentially the target of higher order calls, exported procedures must use only the regular registers for argument passing. This can lead to more (un)boxing than if floats were simply always boxed. Until this is solved, float registers must be enabled explicitly with the developer only option `--use-float-registers'. The other aspect of this change is using two consecutive stack slots to hold a single double variable. Without that, the benefit of passing unboxed floats via dedicated float registers would be largely eroded. compiler/options.m: Add developer option `--use-float-registers'. compiler/handle_options.m: Disable `--use-float-registers' if floats are not wider than words. compiler/make_hlds_passes.m: If `--use-float-registers' is in effect, enable a previous change that allows float constructor arguments to be stored unboxed in structures. compiler/hlds_llds.m: Move `reg_type' here from llds.m and `reg_f' option. Add stack slot width to `stack_slot' type. Add register type and stack slot width to `abs_locn' type. Remember next available float register in `abs_follow_vars'. compiler/hlds_pred.m: Add register type to `arg_loc' type. compiler/llds.m: Add a new kind of lval: double-width stack slots. These are used to hold double-precision floating point values only. Record setting of `--use-float-registers' in exprn_opts. Conform to addition of float registers and double stack slots. compiler/code_info.m: Make predicates take the register type as an argument, where it can no longer be assumed. Remember whether float registers are being used. Remember max float register for calls to MR_trace. Count double width stack slots as two slots. compiler/arg_info.m: Allocate float registers for procedure arguments when appropriate. Delete unused predicates. compiler/var_locn.m: Make predicates working with registers either take the register type as an argument, or handle both register types at once. Select float registers for variables when appropriate. compiler/call_gen.m: Explicitly use regular registers for all higher-order calls, which was implicit before. compiler/pragma_c_gen.m: Use float registers, when available, at the interface between Mercury code and C foreign_procs. compiler/export.m: Whether a float rval needs to be boxed/unboxed when assigned to/from a register depends on the register type. compiler/fact_table.m: Use float registers for arguments to predicates defined by fact tables. compiler/stack_alloc.m: Allocate two consecutive stack slots for float variables when appropriate. compiler/stack_layout.m: Represent double-width stack slots in procedure layout structures. Conform to changes. compiler/store_alloc.m: Allocate float registers (if they exist) for float variables. compiler/use_local_vars.m: Substitute float abstract machine registers with MR_Float local variables. compiler/llds_out_data.m: compiler/llds_out_instr.m: Output float registers and double stack slots. compiler/code_util.m: compiler/follow_vars.m: Count float registers separately from regular registers. compiler/layout.m: compiler/layout_out.m: compiler/trace_gen.m: Remember the max used float register for calls to MR_trace(). compiler/builtin_lib_types.m: Fix incorrect definition of float_type_ctor. compiler/bytecode_gen.m: compiler/continuation_info.m: compiler/disj_gen.m: compiler/dupelim.m: compiler/exprn_aux.m: compiler/global_data.m: compiler/hlds_out_goal.m: compiler/jumpopt.m: compiler/llds_to_x86_64.m: compiler/lookup_switch.m: compiler/opt_debug.m: compiler/opt_util.m: compiler/par_conj_gen.m: compiler/proc_gen.m: compiler/string_switch.m: compiler/tag_switch.m: compiler/tupling.m: compiler/x86_64_regs.m: Conform to changes. runtime/mercury_engine.h: Add an array of fake float "registers" to the Mercury engine structure, when MR_Float is wider than MR_Word. runtime/mercury_regs.h: Document float registers in the Mercury abstract machine. Add macros to access float registers in the Mercury engine. runtime/mercury_stack_layout.h: Add new MR_LongLval cases to represent double-width stack slots. MR_LONG_LVAL_TAGBITS had to be increased to accomodate the new cases, which increases the number of integers in [0, 2^MR_LONG_LVAL_TAGBITS) equal to 0 modulo 4. These are the new MR_LONG_LVAL_TYPE_CONS_n cases. Add max float register field to MR_ExecTrace. runtime/mercury_layout_util.c: runtime/mercury_layout_util.h: Extend MR_copy_regs_to_saved_regs and MR_copy_saved_regs_to_regs for float registers. Understand how to look up new kinds of MR_LongLval: MR_LONG_LVAL_TYPE_F (previously unused), MR_LONG_LVAL_TYPE_DOUBLE_STACKVAR, MR_LONG_LVAL_TYPE_DOUBLE_FRAMEVAR. Conform to the new MR_LONG_LVAL_TYPE_CONS_n cases. runtime/mercury_float.h: Delete redundant #ifdef. runtime/mercury_accurate_gc.c: runtime/mercury_agc_debug.c: Conform to changes (untested). trace/mercury_trace.c: trace/mercury_trace.h: trace/mercury_trace_declarative.c: trace/mercury_trace_external.c: trace/mercury_trace_internal.c: trace/mercury_trace_spy.c: trace/mercury_trace_vars.c: trace/mercury_trace_vars.h: Handle float registers in the trace subsystem. This is mostly a matter of saving/restoring them as with regular registers.
This directory holds the trace subsystem, i.e. the part of the Mercury debugger that is written in C code. Notes on interfacing with other subsystems ------------------------------------------ If tracing is enabled, the compiler includes calls to MR_trace() in the generated C code. The trace subsystem in this directory is therefore called directly from Mercury code, via MR_trace() in runtime/mercury_trace_base.c. One of the first things it does is to save the original values of the Mercury registers in a variable called `saved_regs'. The reason it needs to do this is that the code here may modify registers, e.g. by allocating memory using incr_hp or by calling Mercury code. Once the original values of the registers have been saved, the trace subsystem is free to modify the Mercury registers. So for all code in this directory, the usual convention is that the original values of the Mercury registers are in `saved_regs', while the current (scratch) values for the normal non-transient Mercury registers etc. are in their normal locations, not in the fake_reg copies, and the transient (register window) registers, if any, are in the fake_reg copies. Any code which uses macros such as incr_hp(), list_cons(), make_aligned_string(), etc. that modify the heap pointer must call restore_transient_regs() beforehand and must call save_transient_regs() afterwards. The simplest way to do this is to use the macro MR_TRACE_USE_HP() in trace/mercury_trace_util.h. The tracer may invoke Mercury code defined in the browser or library directories if that code is exported to C using `pragma export'. But any calls from functions here to code defined in Mercury and exported using `pragma export', i.e. functions starting with `ML_' prefixes, must be preceded by a call to save_registers() and followed by a call to restore_registers(). The simplest way to do this is to use the macro MR_TRACE_CALL_MERCURY() in trace/mercury_trace_util.h.