In Thumb1, only one variant is supported: CPS{effect} {flags}
Thumb2 supports three:
CPS{effect}.W {flags}
CPS{effect} {flags} {mode}
CPS {mode}
Canonically, .W should be used only when ambiguity is present between encodings of different width.
The wide suffix is still accepted for the latter two forms via aliases.
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The long encoding for Thumb2 unconditional branches is broken.
Additionally, there is no range checking for target operands; as such
for instructions originating in assembly code, only short Thumb encodings
are generated, regardless of the bitsize needed for the offset.
Adding range checking is non trivial due to the representation of Thumb
branch instructions. There is no true difference between conditional and
unconditional branches in terms of operands and syntax - even unconditional
branches have a predicate which is expected to match that of the IT block
they are in. Yet, the encodings and the permitted size of the offset differ.
Due to this, for any mnemonic there are really 4 encodings to choose for.
The problem cannot be handled in the parser alone or by manipulating td files.
Because the parser builds first a set of match candidates and then checks them
one by one, whatever tablegen-only solution might be found will ultimately be
dependent of the parser's evaluation order. What's worse is that due to the fact
that all branches have the same syntax and the same kinds of operands, that
order is governed by the lexicographical ordering of the names of operand
classes...
To circumvent all this, any necessary disambiguation is added to the instruction
validation pass.
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While the .td entry is nice and all, it takes a pretty gross hack in
ARMAsmParser::ParseInstruction() because of handling of other "subs"
instructions to get it to match. Ran it by Jim Grosbach and he said it was
about what he expected to make this work given the existing code.
rdar://14214063
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instructions. With this patch:
1. ldr.n is recognized as mnemonic for the short encoding
2. ldr.w is recognized as menmonic for the long encoding
3. ldr will map to either short or long encodings depending on the size of the offset
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This adds an instruction alias to make the assembler recognize the alternate literal form: pli [PC, #+/-<imm>]
See A8.8.129 in the ARM ARM (DDI 0406C.b).
Fixes <rdar://problem/14403733>.
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This adds a new decoder table/namespace 'VFPV8', as these instructions have their
top 4 bits as 0b1111, while other Thumb instructions have 0b1110.
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Before the fix Thumb2 instructions of type "add rD, rN, #imm" (T3 encoding, see ARM ARM A8.8.4) with rD and rN both being low registers (r0-r7) were classified as having the T4 encoding.
The T4 encoding doesn't have a cc_out operand so for above instructions the operand gets erroneously removed, corrupting the token stream and leading to parse errors later in the process.
This bug prevented "add r1, r7, #0xcbcbcbcb" from being assembled correctly.
Fixes <rdar://problem/14224440>.
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1. it should accept only 4-byte aligned addresses
2. the maximum offset should be 1020
3. it should be encoded with the offset scaled by two bits
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According to ARM EHABI section 9.2, if the
__aeabi_unwind_cpp_pr1() or __aeabi_unwind_cpp_pr2() is
used, then the handler data must be emitted after the unwind
opcodes. The handler data consists of several words, and
should be terminated by zero.
In case that the .handlerdata directive is not specified by
the programmer, we should emit zero to terminate the handler
data.
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The mapping between SRS pseudo-instructions and SRS native instructions was incorrect, the correct mapping is:
srsfa -> srsib
srsea -> srsia
srsfd -> srsdb
srsed -> srsda
This fixes <rdar://problem/14214734>.
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algorithm when assigning EnumValues to the synthesized registers.
The current algorithm, LessRecord, uses the StringRef compare_numeric
function. This function compares strings, while handling embedded numbers.
For example, the R600 backend registers are sorted as follows:
T1
T1_W
T1_X
T1_XYZW
T1_Y
T1_Z
T2
T2_W
T2_X
T2_XYZW
T2_Y
T2_Z
In this example, the 'scaling factor' is dEnum/dN = 6 because T0, T1, T2
have an EnumValue offset of 6 from one another. However, in other parts
of the register bank, the scaling factors are different:
dEnum/dN = 5:
KC0_128_W
KC0_128_X
KC0_128_XYZW
KC0_128_Y
KC0_128_Z
KC0_129_W
KC0_129_X
KC0_129_XYZW
KC0_129_Y
KC0_129_Z
The diff lists do not work correctly because different kinds of registers have
different 'scaling factors'. This new algorithm, LessRecordRegister, tries to
enforce a scaling factor of 1. For example, the registers are now sorted as
follows:
T1
T2
T3
...
T0_W
T1_W
T2_W
...
T0_X
T1_X
T2_X
...
KC0_128_W
KC0_129_W
KC0_130_W
...
For the Mips and R600 I see a 19% and 6% reduction in size, respectively. I
did see a few small regressions, but the differences were on the order of a
few bytes (e.g., AArch64 was 16 bytes). I suspect there will be even
greater wins for targets with larger register files.
Patch reviewed by Jakob.
rdar://14006013
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Unfortunately this addresses two issues (by the time I'd disentangled the logic
it wasn't worth putting it back to half-broken):
+ Coprocessor instructions should all be predicable in Thumb mode.
+ BKPT should never be predicable.
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The barrier instructions are only "always-execute" in ARM mode, they can quite
happily sit inside an IT block in Thumb.
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In thumb1, NOP is a pseudo-instruction equivalent to mov r8, r8.
However the disassembler should not use this alias.
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The cdp2 instruction should have the same restrictions as cdp on the
co-processor registers.
VFP instructions on v8/AArch32 share the same encoding space as cdp2.
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"When assembling to the ARM instruction set, the .N qualifier produces
an assembler error and the .W qualifier has no effect."
In the pre-matcher handler in the asm parser the ".w" (wide) qualifier
when in ARM mode is now discarded. And an error message is now
produced when the ".n" (narrow) qualifier is used in ARM mode.
Test cases for these were added.
rdar://14064574
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When using a positive offset, literal loads where encoded
as if it was negative, because:
- The sign bit was not assigned to an operand
- The addrmode_imm12 operand was not encoding the sign bit correctly
This patch also makes the assembler look at the .w/.n specifier for
loads.
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Negative zero is returned by the primary expression parser as INT32_MIN, so all that the method needs to do is to accept this value.
Behavior already present for Thumb2.
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- Don't use assert(0), or tests may pass or fail according to assertions.
- For now, The tests are marked as XFAIL for win32 hosts.
FIXME: Could we avoid XFAIL to specify triple in the RUN lines?
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Some ARM CPUs only support ARM mode (ancient v4 ones, for example) and some
only support Thumb mode (M-class ones currently). This makes sure such CPUs
default to the correct mode and makes the AsmParser diagnose an attempt to
switch modes incorrectly.
rdar://14024354
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Changes to ARM unwind opcode assembler:
* Fix multiple .save or .vsave directives. Besides, the
order is preserved now.
* For the directives which will generate multiple opcodes,
such as ".save {r0-r11}", the order of the unwind opcode
is fixed now, i.e. the registers with less encoding value
are popped first.
* Fix the $sp offset calculation. Now, we can use the
.setfp, .pad, .save, and .vsave directives at any order.
Changes to test cases:
* Add test cases to check the order of multiple opcodes
for the .save directive.
* Fix the incorrect $sp offset in the test case. The
stack pointer offset specified in the test case was
incorrect. (Changed test cases: ehabi-mc-section.ll and
ehabi-mc.ll)
* The opcode to restore $sp are slightly reordered. The
behavior are not changed, and the new output is same
as the output of GNU as. (Changed test cases:
eh-directive-pad.s and eh-directive-setfp.s)
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These instructions are deprecated oddities, but we still need to be able to
disassemble (and reassemble) them if and when they're encountered.
Patch by Amaury de la Vieuville.
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