When trying to convert a loading instruction into a FAULTING_LOAD, we
sometimes face code like this:
if %R10 is not null:
%R9<def> = MOV32ri Immediate
%R9<def, tied> = AND32rm %R9, 0x20(%R10)
else:
goto TRAP
In these cases we would like to use the AND32rm instruction as the
faulting operation by hoisting the "depedency" def-ing %R9 also above
the control flow, transforming the program into:
%R9<def> = MOV32ri Immediate
%R9<def, tied> = FAULTING_LOAD_OP(AND32rm %R9, 0x20(%R10), FailPath: TRAP)
This change teaches ImplicitNullChecks to do the above, when safe.
llvm-svn: 273501
The replaced load may have implicit-defs and those defs may be used
in the block of the original load. Make sure to update the liveness
accordingly.
This is a generalization of r267817.
llvm-svn: 268412
This operation may branch to the handler block and we do not want it
to happen anywhere within the basic block.
Moreover, by marking it "terminator and branch" the machine verifier
does not wrongly assume (because of AnalyzeBranch not knowing better)
the branch is analyzable. Indeed, the target was seeing only the
unconditional branch and not the faulting load op and thought it was
a simple unconditional block.
The machine verifier was complaining because of that and moreover,
other optimizations could have done wrong transformation!
In the process, simplify the representation of the handler block in
the faulting load op. Now, we directly reference the handler block
instead of using a label. This has the benefits of:
1. MC knows how to issue a label for a BB, so leave that to it.
2. Accessing the target BB from its label is painful, whereas it is
direct from a MBB operand.
Note: The 2 bytes offset in implicit-null-check.ll comes from the
fact the unconditional jumps are not removed anymore, as the whole
terminator sequence is not analyzable anymore.
Will fix it in a subsequence commit.
llvm-svn: 268327
We basically replace:
HoistBB:
cond_br NullBB, NotNullBB
NullBB:
...
NotNullBB:
<reg> = load
into
HoistBB
<reg> = load_faulting_op NullBB
uncond_br NotNullBB
NullBB:
...
NotNullBB: ## <reg> is now live-in of NotNullBB
...
This partially fixes the machine verifier error for
test/CodeGen/X86/implicit-null-check.ll, but it still fails because
of the implicit CFG structure.
llvm-svn: 267817
MachineFunctionProperties represents a set of properties that a MachineFunction
can have at particular points in time. Existing examples of this idea are
MachineRegisterInfo::isSSA() and MachineRegisterInfo::tracksLiveness() which
will eventually be switched to use this mechanism.
This change introduces the AllVRegsAllocated property; i.e. the property that
all virtual registers have been allocated and there are no VReg operands
left.
With this mechanism, passes can declare that they require a particular property
to be set, or that they set or clear properties by implementing e.g.
MachineFunctionPass::getRequiredProperties(). The MachineFunctionPass base class
verifies that the requirements are met, and handles the setting and clearing
based on the delcarations. Passes can also directly query and update the current
properties of the MF if they want to have conditional behavior.
This change annotates the target-independent post-regalloc passes; future
changes will also annotate target-specific ones.
Reviewers: qcolombet, hfinkel
Differential Revision: http://reviews.llvm.org/D18421
llvm-svn: 264593
Summary: This patch adds enum value for an existing metadata type -- make.implicit. Using preassigned enum will be helpful to get compile time type checking and avoid string construction and comparison. The patch also changes uses of make.implicit from string metadata to enum metadata. There is no functionality change.
Reviewers: reames
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D11698
llvm-svn: 243954
Summary:
This change generalizes the implicit null checks pass to work with
instructions that don't have any explicit register defs. This lets us
use X86's `cmp` against memory as faulting load instructions.
Reviewers: reames, JosephTremoulet
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D11286
llvm-svn: 242703
Summary:
Before this change ImplicitNullChecks would only pick loads of the form:
```
test Reg, Reg
jz elsewhere
fallthrough:
movl 32(Reg), Reg2
```
but not (say)
```
test Reg, Reg
jz elsewhere
fallthrough:
inc Reg3
movl 32(Reg), Reg2
```
This change teaches ImplicitNullChecks to look through "unrelated"
instructions like `inc Reg3` when searching for a load instruction
to convert to a trapping load.
Reviewers: atrick, JosephTremoulet, reames
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D11044
llvm-svn: 241850
Summary:
This change introduces a !make.implicit metadata that allows the
frontend to pre-select the set of explicit null checks that will be
considered for transformation into implicit null checks.
The reason for not using profiling data instead of !make.implicit is
explained in the change to `FaultMaps.rst`.
Reviewers: atrick, reames, pgavlin, JosephTremoulet
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D10824
llvm-svn: 241116
The patch is generated using this command:
tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
-checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
llvm/lib/
Thanks to Eugene Kosov for the original patch!
llvm-svn: 240137
Sanjoy Das