Changes:
* Adds a new generic instruction, SELECTIF, that does value selection (a la
conditional move) similarly to existing SELECT, except that it is
controlled by condition code input and flags-register inputs.
* Adds a new Intel x86_64 variant, 'baseline', that supports SSE2 and
nothing else.
* Adds new Intel x86_64 instructions BSR and BSF.
* Implements generic CLZ, CTZ and POPCOUNT on x86_64 'baseline' targets
using the new BSR, BSF and SELECTIF instructions.
* Implements SELECTIF on x86_64 targets using conditional-moves.
* new test filetests/isa/intel/baseline_clz_ctz_popcount.cton
(for legalization)
* new test filetests/isa/intel/baseline_clz_ctz_popcount_encoding.cton
(for encoding)
* Allow lib/cretonne/meta/gen_legalizer.py to generate non-snake-caseified
Rust without rustc complaining.
Fixes#238.
The fuzzer bugs #219 and #227 are both cases where the register
allocator coloring pass "runs out of registers". What's really happening
is that the constraint solver failed to find a solution, even when one
existed.
Suppose we have three solver variables:
v0(GPR, out, global)
v1(GPR, in)
v2(GPR, in, out)
And suppose registers %r0 and %r1 are available on both input and output
sides of the instruction, but only %r1 is available for global outputs.
A valid solution would be:
v0 -> %r1
v1 -> %r1
v2 -> %r0
However, the solver would pick registers for the three values in
numerical order because v1 and v2 have the same domain size (=2). This
would assign v1 -> %r0 and then fail to find a free register for v2.
Fix this by prioritizing in+out variables over single-sided variables
even when their domains are equal. This means the v2 gets assigned a
register before v1, and it gets a chance to pick a register that is
still available on both in and out sides.
Also try to avoid depending on value numbers in the solver. These bugs
were hard to reproduce because a test case invariably would have
different value numbers, causing the solver to order its variables
differently and succeed. Throw in the previous solution and original
register assignments as tie breakers which are stable and not dependent
on value numbers.
This is still not a substitute for a proper solver search algorithm that
we will probably have to write eventually.
Fixes#219Fixes#227
The error exposed by this test case no longer happens after the
coalescer was rewritten to to follow the Budimlic paper. It's still a
good coalescer test.
Fixes#216 by including the test case.
The Intel instruction "v1 = ushr v2, v2" will implicitly fix the output
register for v2 to %rcx because the output is tied to the first input
operand and the second input operand is fixed to %rcx.
Make sure we handle this transitive constraint when checking for
interference with the globally live registers.
Fixes#218
When the coloring pass sees an instruction with a fixed input register
constraint that is already satisfied, make sure to tell the solver
about it anyway.
There are situations where the solver wants to convert a value to a
solver variable, and we can't allow that if the same value is also used
for a fixed register operand.
Fixes#221.
The spiller wasn't tracking register pressure correctly for dead EBB
parameters in visit_ebb_header(). Make sure we free any dead EBB
parameters.
Fixes#223
The old coalescing algorithm had some algorithmic complexity issues when
dealing with large virtual registers. Reimplement to use a proper
union-find algorithm so we only need one pass through the dominator
forests for virtual registers that are interference free.
Virtual registers that do have interference are split and new registers
built.
This pass is about twice as fast as the old one when dealing with
complex virtual registers.
Ghost instructions and values are supposed to be stored as metadata
alongside the compiled program such that the ghost values can be
computed from the real register/stack values when the program is stopped
for debugging or de-optimization.
If we allow an EBB parameter to be a ghost value, we have no way of
computing its real value using ghost instructions. We would need to know
a complete execution trace of the stopped program to figure out which
values were passed to the ghost parameter.
Instead we require EBB parameters to be real values materialized in
registers or on the stack. We use the regclass_for_abi_type() TargetIsa
callback to determine the initial register class for these parameters.
They can then be spilled later if needed.
Fixes#215.
We want to disable dominance checks in unreachable code. The
is_reachable() check for EBB parameter values was checking if the
defining EBB was reachable, not the EBB using the value.
This bug showed up in fuzzing and in #213.
Add an addend field to reloc_external, and use it to move the
responsibility for accounting for the difference between the end of an
instruction (where the PC is considered to be in PC-relative on intel)
and the beginning of the immediate field into the encoding code.
Specifically, this makes IntelGOTPCRel4 directly correspond to
R_X86_64_GOTPCREL, instead of also carrying an implicit `- 4`.
When the spiller needs to make a register available for a conditional
branch instruction, it can be necessary to spill some of the EBB
arguments on the branch instruction. This is ok because EBB argument
values belong to the same virtual register as the corresponding EBB
parameter and we spill the whole virtreg to the same slot.
Also make sure free_regs() can handle values that are killed by the
current instruction *and* spilled.
The stack implementation if the Budimlic dominator forest doesn't work
correctly with a CFG RPO. It needs the domtree pre-order.
Also handle EBB pre-order vs inst-level preorder. Manage the stack
according to EBB dominance. Look for a dominating value by searching the
stack. This is different from the Budimlic algorithm because we're
computing the dominator tree pre-order with EBB granularity only.
Fixes#207.
The coalescer makes sure that matching EBB arguments and parameters are
always in the same virtual registers, and therefore also in the same
stack slot if they are spilled.
This means that the reload pass should never rewrite an EBB argument if
the argument value is spilled. This comes up in cases where the branch
instruction needs the same value in a register:
brnz v9, ebb3(v9)
If the virtual register containing v9 is spilled, the branch instruction
must be reloaded like:
v52 = fill v9
brnz v52, ebb3(v9)
The branch register argument must be rewritten, and the EBB argument
must be referring to the original stack value.
Fixes#208.
Add a DominatorTreePreorder data structure which can be initialized for
a DominatorTree and used for queries involving a pre-order of the
dominator tree.
Print out the pre-order and send it through filecheck in "test domtree"
file tests.
Add a "cfg_postorder:" printout to the "test domtree" file tests and use
that to check the computed CFG post-order instead of doing it manually
with Rust code.
* Use imm64 rather than offset32
* Add predicate to enforce signed 32-bit limit to imm
* Remove AdjustSpImm format
* Add encoding tests for adjust_sp_imm
* Adjust use of adjust_sp_imm in Intel prologue_epilogue to match
These tests were only using "test compile" because it doesn't require
any filecheck directives to be present, so just stop requiring filecheck
directives for "test regalloc" and other filecheck-based test drivers.
Fixes#178.
When an instruction with a fixed output operand defines a globally live
SSA value, we need to check if the fixed register is available in the
`regs.global` set of registers that can be used across EBB boundaries.
If the fixed output register is not available in regs.global, set the
replace_global_defines flag so the output operands are rewritten as
local values.
Fixes#175.
The Intel division instructions have fixed input operands that are
clobbered by fixed output operands, so the value passed as an input will
be clobbered just like a tied operand.
The FixedTied operand constraint is used to indicate a fixed input
operand that has a corresponding output operand with the same fixed
register.
Teach the spiller to teach a FixedTied operand the same as a Tied
operand constraint and make sure that the input value is killed by the
instruction.
Add EBB parameter and EBB argument to the langref glossary to clarify
the distinction between formal EBB parameter values and arguments passed
to branches.
- Replace "ebb_arg" with "ebb_param" in function names that deal with
EBB parameters.
- Rename the ValueDef variants to Result and Param.
- A bunch of other small langref fixes.
No functional changes intended.
This allows GVN to avoid hoisting them. These will be to coarse for
things that want more precise dependence information, however we can
work that out when we build such things.
Add integer and floating comparison instructions that return CPU flags:
ifcmp, ifcmp_imm, and ffcmp.
Add conditional branch instructions that check CPU flags: brif, brff
Add instructions that check a condition in the CPU flags and return a
b1: trueif, trueff.
