Some register-register instructions can be encoded in 2 different ways, this happens when 2 register operands can be folded (separately).
For example if we look at the MOV8rr and MOV8rr_REV, both instructions perform exactly the same operation, but are encoded differently. Here is the relevant information about these instructions from Intel's 64-ia-32-architectures-software-developer-manual:
Opcode Instruction Op/En 64-Bit Mode Compat/Leg Mode Description
8A /r MOV r8,r/m8 RM Valid Valid Move r/m8 to r8.
88 /r MOV r/m8,r8 MR Valid Valid Move r8 to r/m8.
Here we can see that in order to enable the folding of the output and input registers, we had to define 2 "encodings", and as a result we got 2 move 8-bit register-register instructions.
In the X86 backend, we define both of these instructions, usually one has a regular name (MOV8rr) while the other has "_REV" suffix (MOV8rr_REV), must be marked with isCodeGenOnly flag and is not emitted from CodeGen.
Automatically generating the memory folding tables relies on matching encodings of instructions, but in these cases where we want to map both memory forms of the mov 8-bit (MOV8rm & MOV8mr) to MOV8rr (not to MOV8rr_REV) we have to somehow point from the MOV8rr_REV to the "regular" appropriate instruction which in this case is MOV8rr.
This field enable this "pointing" mechanism - which is used in the TableGen backend for generating memory folding tables.
Differential Revision: https://reviews.llvm.org/D32683
llvm-svn: 304087
This patch handles 64-bit constants which can be encoded as 32-bit immediates.
It extends the functionality added by https://reviews.llvm.org/D11363 for 32-bit constants to 64-bit constants.
Patch by Sunita Marathe!
Differential Revision: https://reviews.llvm.org/D23391
llvm-svn: 278857
First step in preventing immediates that occur more than once within a single
basic block from being pulled into their users, in order to prevent unnecessary
large instruction encoding .Currently enabled only when optimizing for size.
Patch by: zia.ansari@intel.com
Differential Revision: http://reviews.llvm.org/D11363
llvm-svn: 244601
Overall this seems simpler. It reduces duplication of patterns between both modes and it simplifies the memory folding/unfolding tables as they don't need to create fake instructions just to keep track of 64-bitness.
llvm-svn: 225252
These should end up (in ELF) as R_X86_64_32S relocs, not R_X86_64_32.
Kill the horrid and incomplete special case and FIXME in
EncodeInstruction() and set things up so it can infer the signedness
from the ImmType just like it can the size and whether it's PC-relative.
llvm-svn: 200495
This fixes the bulk of 16-bit output, and the corresponding test case
x86-16.s now looks mostly like the x86-32.s test case that it was
originally based on. A few irrelevant instructions have been dropped,
and there are still some corner cases to be fixed in subsequent patches.
llvm-svn: 198752
That's what it actually means, and with 16-bit support it's going to be
a little more relevant since in a few corner cases we may actually want
to distinguish between 16-bit and 32-bit mode (for example the bare 'push'
aliases to pushw/pushl etc.)
Patch by David Woodhouse
llvm-svn: 197768
Implements Instruction scheduler latencies for Silvermont,
using latencies from the Intel Silvermont Optimization Guide.
Auto detects SLM.
Turns on post RA scheduler when generating code for SLM.
llvm-svn: 190717
This corrects a problem where x86 instructions that implicitly define/use both
an A-register (RAX, EAX, ..) and EFLAGS were declared as only defining/using
EFLAGS, because the outer "let Defs/Uses = [EFLAGS]" in the various multiclasses
overrides the "let Defs/Uses = [areg]" in BinOpAI.
The instructions deriving from BinOpAI were moved out of the "let Defs", and a
BinOpAI_FF class was created, for instructions that implicitly define and use
EFLAGS and the A-register (SBC, ADC).
llvm-svn: 182883
Now all x86 instructions that have itinerary classes also have SchedRW
lists. This is required before the new scheduling models can be used.
There are still unannotated instructions remaining, but they don't have
itinerary classes either.
llvm-svn: 178051
This new-style scheduling information is going to replace the
instruction iteneraries.
This also serves as a test case for Andy's fix in r177317.
llvm-svn: 177323
1) allows the use of RIP-relative addressing in 32-bit LEA instructions under
x86-64 (ILP32 and LP64)
2) separates the size of address registers in 64-bit LEA instructions from
control by ILP32/LP64.
llvm-svn: 174208
We perform the following:
1> Use SUB instead of CMP for i8,i16,i32 and i64 in ISel lowering.
2> Modify MachineCSE to correctly handle implicit defs.
3> Convert SUB back to CMP if possible at peephole.
Removed pattern matching of (a>b) ? (a-b):0 and like, since they are handled
by peephole now.
rdar://11873276
llvm-svn: 161462
Updated OptimizeCompare in peephole to remove redundant cmp against zero.
We only remove Compare if CF and OF are not used.
rdar://11855129
llvm-svn: 160454
Ayman Musa