[mips] Use less registers to load address of TargetExternalSymbol
There is no pattern matched `add hi, (MipsLo texternalsym)`. As a
result, loading an address of 32-bit symbol requires two registers
and one more additional instruction:
```
addiu $1, $zero, %lo(foo)
lui $2, %hi(foo)
addu $25, $2, $1
```
This patch adds the missed pattern and enables generation more
effective set of instructions:
```
lui $1, %hi(foo)
addiu $25, $1, %lo(foo)
```
Differential Revision: https://reviews.llvm.org/D66771
llvm-svn: 370196
Merge commit 59bb3609f from llvm git (by Simon Atanasyan):
[mips] Fix 64-bit address loading in case of applying 32-bit mask to
the result
If result of 64-bit address loading combines with 32-bit mask, LLVM
tries to optimize the code and remove "redundant" loading of upper
32-bits of the address. It leads to incorrect code on MIPS64 targets.
MIPS backend creates the following chain of commands to load 64-bit
address in the `MipsTargetLowering::getAddrNonPICSym64` method:
```
(add (shl (add (shl (add %highest(sym), %higher(sym)),
16),
%hi(sym)),
16),
%lo(%sym))
```
If the mask presents, LLVM decides to optimize the chain of commands.
It really does not make sense to load upper 32-bits because the
0x0fffffff mask anyway clears them. After removing redundant commands
we get this chain:
```
(add (shl (%hi(sym), 16), %lo(%sym))
```
There is no patterns matched `(MipsHi (i64 symbol))`. Due a bug in
`SYM_32` predicate definition, backend incorrectly selects a pattern
for a 32-bit symbols and uses the `lui` instruction for loading
`%hi(sym)`.
As a result we get incorrect set of instructions with unnecessary
16-bit left shifting:
```
lui at,0x0
R_MIPS_HI16 foo
dsll at,at,0x10
daddiu at,at,0
R_MIPS_LO16 foo
```
This patch resolves two problems:
- Fix `SYM_32/SYM_64` predicates to prevent selection of patterns
dedicated to 32-bit symbols in case of using N64 ABI.
- Add missed patterns for 64-bit symbols for `%hi/%lo`.
Fix PR42736.
Differential Revision: https://reviews.llvm.org/D66228
llvm-svn: 370268
These two commits fix a miscompilation of the kernel for mips64, and
should allow clang to be used as the default compiler for mips64.
Requested by: arichards
MFC after: 3 days
629d75a260