This adds support for parsing and emitting the SBREL relocation variant for the
ARM target. Handling this relocation variant is necessary for supporting the
full ARM ELF specification. Addresses PR22128.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225595 91177308-0d34-0410-b5e6-96231b3b80d8
.lower() the Name and compare only the lowecase. Removing 81 compares/lines of
code. This changes the accepted string to be mixed lower/upper case but it
should be ok.
Discussed with Jim Grosbach.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224547 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Currently, it supports generating, but not parsing, this expression.
Test added as well.
Test Plan: New test added, no regressions due to this.
Reviewers: hfinkel
Reviewed By: hfinkel
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D6672
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224415 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Large-model was added first. With the addition of support for multiple PIC
models in LLVM, now add small-model PIC for 32-bit PowerPC, SysV4 ABI. This
generates more optimal code, for shared libraries with less than about 16380
data objects.
Test Plan: Test cases added or updated
Reviewers: joerg, hfinkel
Reviewed By: hfinkel
Subscribers: jholewinski, mcrosier, emaste, llvm-commits
Differential Revision: http://reviews.llvm.org/D5399
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221791 91177308-0d34-0410-b5e6-96231b3b80d8
Nico Rieck added support for this 32-bit COFF relocation some time ago
for Win64 stuff. It appears that as an oversight, the assembly output
used "foo"@IMGREL32 instead of "foo"@IMGREL, which is what we can parse.
Sadly, there were actually tests that took in IMGREL and put out
IMGREL32, and we didn't notice the inconsistency. Oh well. Now LLVM can
assemble it's own output with slightly more fidelity.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218437 91177308-0d34-0410-b5e6-96231b3b80d8
The fix itself is fairly simple: move getAccessVariant to MCValue so that we
replace the old weak expression evaluation with the far more general
EvaluateAsRelocatable.
This then requires that EvaluateAsRelocatable stop when it finds a non
trivial reference kind. And that in turn requires the ELF writer to look
harder for weak references.
Last but not least, this found a case where we were being bug by bug
compatible with gas and accepting an invalid input. I reported pr19647
to track it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207920 91177308-0d34-0410-b5e6-96231b3b80d8
When evaluating an assembly expression for a relocation, we want to
stop at MCSymbols that are in the symbol table, even if they are variables.
This is needed since the semantics may require that the relocation use them.
That is not the case when computing the value of a symbol in the symbol table.
There are no relocations in this case and we have to keep going until we hit
a section or find out that the expression doesn't have an assembly time
value.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207445 91177308-0d34-0410-b5e6-96231b3b80d8
I discovered this const-hole while attempting to coalesnce the Symbol
and SymbolMap data structures. There's some pending issues with that,
but I figured this change was easy to flush early.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207124 91177308-0d34-0410-b5e6-96231b3b80d8
definition below all the header #include lines. This updates most of the
miscellaneous other lib/... directories. A few left though.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206845 91177308-0d34-0410-b5e6-96231b3b80d8
This adds a second implementation of the AArch64 architecture to LLVM,
accessible in parallel via the "arm64" triple. The plan over the
coming weeks & months is to merge the two into a single backend,
during which time thorough code review should naturally occur.
Everything will be easier with the target in-tree though, hence this
commit.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205090 91177308-0d34-0410-b5e6-96231b3b80d8
Given
bar = foo + 4
.long bar
MC would eat the 4. GNU as includes it in the relocation. The rule seems to be
that a variable that defines a symbol is used in the relocation and one that
does not define a symbol is evaluated and the result included in the relocation.
Fixing this unfortunately required some other changes:
* Since the variable is now evaluated, it would prevent the ELF writer from
noticing the weakref marker the elf streamer uses. This patch then replaces
that with a VariantKind in MCSymbolRefExpr.
* Using VariantKind then requires us to look past other VariantKind to see
.weakref bar,foo
call bar@PLT
doing this also fixes
zed = foo +2
call zed@PLT
so that is a good thing.
* Looking past VariantKind means that the relocation selection has to use
the fixup instead of the target.
This is a reboot of the previous fixes for MC. I will watch the sanitizer
buildbot and wait for a build before adding back the previous fixes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204294 91177308-0d34-0410-b5e6-96231b3b80d8
When printing assembly we don't have a Layout object, but we can still
try to fold some constants.
Testcase by Ulrich Weigand.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203677 91177308-0d34-0410-b5e6-96231b3b80d8
This enhances the ARMAsmParser to handle .tlsdescseq directives. This is a
slightly special relocation. We must be able to generate them, but not consume
them in assembly. The relocation is meant to assist the linker in generating a
TLS descriptor sequence. The ELF target streamer is enhanced to append
additional fixups into the current segment and that is used to emit the new
R_ARM_TLS_DESCSEQ relocations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200448 91177308-0d34-0410-b5e6-96231b3b80d8
Add support for tlsdesc relocations which are part of the ABI, marked as
experimental. These relocations permit the linker to perform TLS reference
optimizations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200447 91177308-0d34-0410-b5e6-96231b3b80d8
This adds support for TLS CALL relocations. TLS CALL relocations are used to
indicate to the linker to generate appropriate entries to resolve TLS references
via an appropriate function invocation (e.g. __tls_get_addr(PLT)).
In order to accomodate the linker relaxation of the TLS access model for the
references (GD/LD -> IE, IE -> LE), the relocation addend must be incomplete.
This requires that the partial inplace value is also incomplete (i.e. 0). We
simply avoid the offset value calculation at the time of the fixup adjustment in
the ARM assembler backend.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200446 91177308-0d34-0410-b5e6-96231b3b80d8
Add support for the symbol(tlsldo) relocation. This is required in order to
solve PR18554.
Reviewed by R. Golin, A. Korobeynikov.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199644 91177308-0d34-0410-b5e6-96231b3b80d8
ARM symbol variants are written with parens instead of @ like this:
.word __GLOBAL_I_a(target1)
This commit adds support for parsing these symbol variants in
expressions. We introduce a new flag to MCAsmInfo that indicates the
parser should use parens to parse the symbol variant. The expression
parser is modified to look for symbol variants using parens instead
of @ when the corresponding MCAsmInfo flag is true.
The MCAsmInfo parens flag is enabled only for ARM on ELF.
By adding this flag to MCAsmInfo, we are able to get rid of
redundant ARM-specific symbol variants and use the generic variants
instead (e.g. VK_GOT instead of VK_ARM_GOT). We use the new
UseParensForSymbolVariant attribute in MCAsmInfo to correctly print
the symbol variants for arm.
To achive this we need to keep a handle to the MCAsmInfo in the
MCSymbolRefExpr class that we can check when printing the symbol
variant.
Updated Tests:
Changed case of symbol variant to match the generic kind.
test/CodeGen/ARM/tls-models.ll
test/CodeGen/ARM/tls1.ll
test/CodeGen/ARM/tls2.ll
test/CodeGen/Thumb2/tls1.ll
test/CodeGen/Thumb2/tls2.ll
PR18080
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196424 91177308-0d34-0410-b5e6-96231b3b80d8
In the commit message to r185476 I wrote:
>The PowerPC-specific modifiers VK_PPC_TLSGD and VK_PPC_TLSLD
>correspond exactly to the generic modifiers VK_TLSGD and VK_TLSLD.
>This causes some confusion with the asm parser, since VK_PPC_TLSGD
>is output as @tlsgd, which is then read back in as VK_TLSGD.
>
>To avoid this confusion, this patch removes the PowerPC-specific
>modifiers and uses the generic modifiers throughout. (The only
>drawback is that the generic modifiers are printed in upper case
>while the usual convention on PowerPC is to use lower-case modifiers.
>But this is just a cosmetic issue.)
This was unfortunately incorrect, there is is fact another,
serious drawback to using the default VK_TLSLD/VK_TLSGD
variant kinds: using these causes ELFObjectWriter::RelocNeedsGOT
to return true, which in turn causes the ELFObjectWriter to emit
an undefined reference to _GLOBAL_OFFSET_TABLE_.
This is a problem on powerpc64, because it uses the TOC instead
of the GOT, and the linker does not provide _GLOBAL_OFFSET_TABLE_,
so the symbol remains undefined. This means shared libraries
using TLS built with the integrated assembler are currently
broken.
While the whole RelocNeedsGOT / _GLOBAL_OFFSET_TABLE_ situation
probably ought to be properly fixed at some point, for now I'm
simply reverting the r185476 commit. Now this in turn exposes
the breakage of handling @tlsgd/@tlsld in the asm parser that
this check-in was originally intended to fix.
To avoid this regression, I'm also adding a different fix for
this problem: while common code now parses @tlsgd as VK_TLSGD,
a special hack in the asm parser translates this code to the
platform-specific VK_PPC_TLSGD that the back-end now expects.
While this is not really pretty, it's self-contained and
shouldn't hurt anything else for now. One the underlying
problem is fixed, this hack can be reverted again.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185945 91177308-0d34-0410-b5e6-96231b3b80d8
The PowerPC-specific modifiers VK_PPC_TLSGD and VK_PPC_TLSLD
correspond exactly to the generic modifiers VK_TLSGD and VK_TLSLD.
This causes some confusion with the asm parser, since VK_PPC_TLSGD
is output as @tlsgd, which is then read back in as VK_TLSGD.
To avoid this confusion, this patch removes the PowerPC-specific
modifiers and uses the generic modifiers throughout. (The only
drawback is that the generic modifiers are printed in upper case
while the usual convention on PowerPC is to use lower-case modifiers.
But this is just a cosmetic issue.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185476 91177308-0d34-0410-b5e6-96231b3b80d8
This adds support for TLS data relocations and modifiers:
.quad target@dtpmod
.quad target@tprel
.quad target@dtprel
Currently exploited by the asm parser only.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185394 91177308-0d34-0410-b5e6-96231b3b80d8
Add VK_... values and relocation types necessary to support
the @got family of modifiers. Used by the asm parser only.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184860 91177308-0d34-0410-b5e6-96231b3b80d8
The current code base only supports the minimum set of tls-related
relocations and @modifiers that are necessary to support compiler-
generated code. This patch extends this to the full set defined
in the ABI (and supported by the GNU assembler) for the benefit
of the assembler parser.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184551 91177308-0d34-0410-b5e6-96231b3b80d8
This adds support for the @higher, @highera, @highest, and @highesta
modifers, including some missing relocation types.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184550 91177308-0d34-0410-b5e6-96231b3b80d8
This adds the relocation type and other necessary infrastructure
to use the @toc@h modifier in the assembler.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184549 91177308-0d34-0410-b5e6-96231b3b80d8
This adds necessary infrastructure to support the @h modifier.
Note that all required relocation types were already present
(and unused).
This patch provides support for using @h in the assembler;
it would also be possible to now use this feature in code
generated by the compiler, but this is not done yet.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184548 91177308-0d34-0410-b5e6-96231b3b80d8
This renames more VK_PPC_ enums, to make them more closely reflect
the @modifier string they represent. This also prepares for adding
a bunch of new VK_PPC_ enums in upcoming patches.
For consistency, some MO_ flags related to VK_PPC_ enums are
likewise renamed.
No change in behaviour.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184547 91177308-0d34-0410-b5e6-96231b3b80d8
This is another minor cleanup; to bring enum names in line
with the corresponding @modifier names, this renames:
VK_PPC_TOC -> VK_PPC_TOCBASE
VK_PPC_TOC_ENTRY -> VK_PPC_TOC16
No code change intended.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184491 91177308-0d34-0410-b5e6-96231b3b80d8
When targeting the Darwin assembler, we need to generate markers ha16() and
lo16() to designate the high and low parts of a (symbolic) immediate. This
is necessary not just for plain symbols, but also for certain symbolic
expression, typically along the lines of ha16(A - B). The latter doesn't
work when simply using VariantKind flags on the symbol reference.
This is why the current back-end uses hacks (explicitly called out as such
via multiple FIXMEs) in the symbolLo/symbolHi print methods.
This patch uses target-defined MCExpr codes to represent the Darwin
ha16/lo16 constructs, following along the lines of the equivalent solution
used by the ARM back end to handle their :upper16: / :lower16: markers.
This allows us to get rid of special handling both in the symbolLo/symbolHi
print method and in the common code MCExpr::print routine. Instead, the
ha16 / lo16 markers are printed simply in a custom print routine for the
target MCExpr types. (As a result, the symbolLo/symbolHi print methods
can now replaced by a single printS16ImmOperand routine that also handles
symbolic operands.)
The patch also provides a EvaluateAsRelocatableImpl routine to handle
ha16/lo16 constructs. This is not actually used at the moment by any
in-tree code, but is provided as it makes merging into David Fang's
out-of-tree Mach-O object writer simpler.
Since there is no longer any need to treat VK_PPC_GAS_HA16 and
VK_PPC_DARWIN_HA16 differently, they are merged into a single
VK_PPC_ADDR16_HA (and likewise for the _LO16 types).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182616 91177308-0d34-0410-b5e6-96231b3b80d8
This patch adds support for PowerPC platform-specific variant
kinds in MCSymbolRefExpr::getVariantKindForName, and also
adds a test case to verify they are translated to the appropriate
fixup type.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181053 91177308-0d34-0410-b5e6-96231b3b80d8
Add support for the COFF relocation types IMAGE_REL_I386_DIR32NB and
IMAGE_REL_AMD64_ADDR32NB for 32- and 64-bit respectively. These are
similar to normal 4-byte relocations except that they do not include
the base address of the image.
Image-relative relocations are used for debug information (32-bit) and
SEH unwind tables (64-bit).
A new MCSymbolRef variant called 'VK_COFF_IMGREL32' is introduced to
specify such relocations. For AT&T assembly, this variant can be accessed
using the symbol suffix '@imgrel'.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179240 91177308-0d34-0410-b5e6-96231b3b80d8
'@SECREL' is what is used by the Microsoft assembler, but GNU as expects '@SECREL32'.
With the patch, the MC-generated code works fine in combination with a recent GNU as (2.23.51.20120920 here).
Patch by David Nadlinger!
Differential Revision: http://llvm-reviews.chandlerc.com/D429
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178427 91177308-0d34-0410-b5e6-96231b3b80d8
for a wider range of GOT entries that can hold thread-relative offsets.
This matches the behavior of GCC, which was not documented in the PPC64 TLS
ABI. The ABI will be updated with the new code sequence.
Former sequence:
ld 9,x@got@tprel(2)
add 9,9,x@tls
New sequence:
addis 9,2,x@got@tprel@ha
ld 9,x@got@tprel@l(9)
add 9,9,x@tls
Note that a linker optimization exists to transform the new sequence into
the shorter sequence when appropriate, by replacing the addis with a nop
and modifying the base register and relocation type of the ld.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170209 91177308-0d34-0410-b5e6-96231b3b80d8
PowerPC target. This is the last of the four models, so we now have
full TLS support.
This is mostly a straightforward extension of the general dynamic model.
I had to use an additional Chain operand to tie ADDIS_DTPREL_HA to the
register copy following ADDI_TLSLD_L; otherwise everything above the
ADDIS_DTPREL_HA appeared dead and was removed.
As before, there are new test cases to test the assembly generation, and
the relocations output during integrated assembly. The expected code
gen sequence can be read in test/CodeGen/PowerPC/tls-ld.ll.
There are a couple of things I think can be done more efficiently in the
overall TLS code, so there will likely be a clean-up patch forthcoming;
but for now I want to be sure the functionality is in place.
Bill
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170003 91177308-0d34-0410-b5e6-96231b3b80d8
Add R_ARM_NONE and R_ARM_PREL31 relocation types
to MCExpr. Both of them will be used while
generating .ARM.extab and .ARM.exidx sections.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169965 91177308-0d34-0410-b5e6-96231b3b80d8
Given a thread-local symbol x with global-dynamic access, the generated
code to obtain x's address is:
Instruction Relocation Symbol
addis ra,r2,x@got@tlsgd@ha R_PPC64_GOT_TLSGD16_HA x
addi r3,ra,x@got@tlsgd@l R_PPC64_GOT_TLSGD16_L x
bl __tls_get_addr(x@tlsgd) R_PPC64_TLSGD x
R_PPC64_REL24 __tls_get_addr
nop
<use address in r3>
The implementation borrows from the medium code model work for introducing
special forms of ADDIS and ADDI into the DAG representation. This is made
slightly more complicated by having to introduce a call to the external
function __tls_get_addr. Using the full call machinery is overkill and,
more importantly, makes it difficult to add a special relocation. So I've
introduced another opcode GET_TLS_ADDR to represent the function call, and
surrounded it with register copies to set up the parameter and return value.
Most of the code is pretty straightforward. I ran into one peculiarity
when I introduced a new PPC opcode BL8_NOP_ELF_TLSGD, which is just like
BL8_NOP_ELF except that it takes another parameter to represent the symbol
("x" above) that requires a relocation on the call. Something in the
TblGen machinery causes BL8_NOP_ELF and BL8_NOP_ELF_TLSGD to be treated
identically during the emit phase, so this second operand was never
visited to generate relocations. This is the reason for the slightly
messy workaround in PPCMCCodeEmitter.cpp:getDirectBrEncoding().
Two new tests are included to demonstrate correct external assembly and
correct generation of relocations using the integrated assembler.
Comments welcome!
Thanks,
Bill
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169910 91177308-0d34-0410-b5e6-96231b3b80d8
on 64-bit PowerPC ELF.
The patch includes code to handle external assembly and MC output with the
integrated assembler. It intentionally does not support the "old" JIT.
For the initial-exec TLS model, the ABI requires the following to calculate
the address of external thread-local variable x:
Code sequence Relocation Symbol
ld 9,x@got@tprel(2) R_PPC64_GOT_TPREL16_DS x
add 9,9,x@tls R_PPC64_TLS x
The register 9 is arbitrary here. The linker will replace x@got@tprel
with the offset relative to the thread pointer to the generated GOT
entry for symbol x. It will replace x@tls with the thread-pointer
register (13).
The two test cases verify correct assembly output and relocation output
as just described.
PowerPC-specific selection node variants are added for the two
instructions above: LD_GOT_TPREL and ADD_TLS. These are inserted
when an initial-exec global variable is encountered by
PPCTargetLowering::LowerGlobalTLSAddress(), and later lowered to
machine instructions LDgotTPREL and ADD8TLS. LDgotTPREL is a pseudo
that uses the same LDrs support added for medium code model's LDtocL,
with a different relocation type.
The rest of the processing is straightforward.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169281 91177308-0d34-0410-b5e6-96231b3b80d8
The default for 64-bit PowerPC is small code model, in which TOC entries
must be addressable using a 16-bit offset from the TOC pointer. Additionally,
only TOC entries are addressed via the TOC pointer.
With medium code model, TOC entries and data sections can all be addressed
via the TOC pointer using a 32-bit offset. Cooperation with the linker
allows 16-bit offsets to be used when these are sufficient, reducing the
number of extra instructions that need to be executed. Medium code model
also does not generate explicit TOC entries in ".section toc" for variables
that are wholly internal to the compilation unit.
Consider a load of an external 4-byte integer. With small code model, the
compiler generates:
ld 3, .LC1@toc(2)
lwz 4, 0(3)
.section .toc,"aw",@progbits
.LC1:
.tc ei[TC],ei
With medium model, it instead generates:
addis 3, 2, .LC1@toc@ha
ld 3, .LC1@toc@l(3)
lwz 4, 0(3)
.section .toc,"aw",@progbits
.LC1:
.tc ei[TC],ei
Here .LC1@toc@ha is a relocation requesting the upper 16 bits of the
32-bit offset of ei's TOC entry from the TOC base pointer. Similarly,
.LC1@toc@l is a relocation requesting the lower 16 bits. Note that if
the linker determines that ei's TOC entry is within a 16-bit offset of
the TOC base pointer, it will replace the "addis" with a "nop", and
replace the "ld" with the identical "ld" instruction from the small
code model example.
Consider next a load of a function-scope static integer. For small code
model, the compiler generates:
ld 3, .LC1@toc(2)
lwz 4, 0(3)
.section .toc,"aw",@progbits
.LC1:
.tc test_fn_static.si[TC],test_fn_static.si
.type test_fn_static.si,@object
.local test_fn_static.si
.comm test_fn_static.si,4,4
For medium code model, the compiler generates:
addis 3, 2, test_fn_static.si@toc@ha
addi 3, 3, test_fn_static.si@toc@l
lwz 4, 0(3)
.type test_fn_static.si,@object
.local test_fn_static.si
.comm test_fn_static.si,4,4
Again, the linker may replace the "addis" with a "nop", calculating only
a 16-bit offset when this is sufficient.
Note that it would be more efficient for the compiler to generate:
addis 3, 2, test_fn_static.si@toc@ha
lwz 4, test_fn_static.si@toc@l(3)
The current patch does not perform this optimization yet. This will be
addressed as a peephole optimization in a later patch.
For the moment, the default code model for 64-bit PowerPC will remain the
small code model. We plan to eventually change the default to medium code
model, which matches current upstream GCC behavior. Note that the different
code models are ABI-compatible, so code compiled with different models will
be linked and execute correctly.
I've tested the regression suite and the application/benchmark test suite in
two ways: Once with the patch as submitted here, and once with additional
logic to force medium code model as the default. The tests all compile
cleanly, with one exception. The mandel-2 application test fails due to an
unrelated ABI compatibility with passing complex numbers. It just so happens
that small code model was incredibly lucky, in that temporary values in
floating-point registers held the expected values needed by the external
library routine that was called incorrectly. My current thought is to correct
the ABI problems with _Complex before making medium code model the default,
to avoid introducing this "regression."
Here are a few comments on how the patch works, since the selection code
can be difficult to follow:
The existing logic for small code model defines three pseudo-instructions:
LDtoc for most uses, LDtocJTI for jump table addresses, and LDtocCPT for
constant pool addresses. These are expanded by SelectCodeCommon(). The
pseudo-instruction approach doesn't work for medium code model, because
we need to generate two instructions when we match the same pattern.
Instead, new logic in PPCDAGToDAGISel::Select() intercepts the TOC_ENTRY
node for medium code model, and generates an ADDIStocHA followed by either
a LDtocL or an ADDItocL. These new node types correspond naturally to
the sequences described above.
The addis/ld sequence is generated for the following cases:
* Jump table addresses
* Function addresses
* External global variables
* Tentative definitions of global variables (common linkage)
The addis/addi sequence is generated for the following cases:
* Constant pool entries
* File-scope static global variables
* Function-scope static variables
Expanding to the two-instruction sequences at select time exposes the
instructions to subsequent optimization, particularly scheduling.
The rest of the processing occurs at assembly time, in
PPCAsmPrinter::EmitInstruction. Each of the instructions is converted to
a "real" PowerPC instruction. When a TOC entry needs to be created, this
is done here in the same manner as for the existing LDtoc, LDtocJTI, and
LDtocCPT pseudo-instructions (I factored out a new routine to handle this).
I had originally thought that if a TOC entry was needed for LDtocL or
ADDItocL, it would already have been generated for the previous ADDIStocHA.
However, at higher optimization levels, the ADDIStocHA may appear in a
different block, which may be assembled textually following the block
containing the LDtocL or ADDItocL. So it is necessary to include the
possibility of creating a new TOC entry for those two instructions.
Note that for LDtocL, we generate a new form of LD called LDrs. This
allows specifying the @toc@l relocation for the offset field of the LD
instruction (i.e., the offset is replaced by a SymbolLo relocation).
When the peephole optimization described above is added, we will need
to do similar things for all immediate-form load and store operations.
The seven "mcm-n.ll" test cases are kept separate because otherwise the
intermingling of various TOC entries and so forth makes the tests fragile
and hard to understand.
The above assumes use of an external assembler. For use of the
integrated assembler, new relocations are added and used by
PPCELFObjectWriter. Testing is done with "mcm-obj.ll", which tests for
proper generation of the various relocations for the same sequences
tested with the external assembler.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168708 91177308-0d34-0410-b5e6-96231b3b80d8
