reserving a physical register ($gp or $28) for that purpose.
This will completely eliminate loads that restore the value of $gp after every
function call, if the register allocator assigns a callee-saved register, or
eliminate unnecessary loads if it assigns a temporary register.
example:
.cpload $25 // set $gp.
...
.cprestore 16 // store $gp to stack slot 16($sp).
...
jalr $25 // function call. clobbers $gp.
lw $gp, 16($sp) // not emitted if callee-saved reg is chosen.
...
lw $2, 4($gp)
...
jalr $25 // function call.
lw $gp, 16($sp) // not emitted if $gp is not live after this instruction.
...
llvm-svn: 151402
- lower unaligned loads/stores.
- encode the size operand of instructions INS and EXT.
- emit relocation information needed for JAL (jump-and-link).
llvm-svn: 145113
"With this patch we can now generate runnable Mips code through LLVM
direct object emission. We have run numerous simple programs, both C
and C++ and with -O0 and -O3 from the output. The code is not production
ready, but quite useful for experimentation." Patch and message by
Jack Carter
llvm-svn: 144414
Mips1 does not support double precision loads or stores, therefore two single
precision loads or stores must be used in place of these instructions. This
patch treats double precision loads and stores as if they are legal
instructions until MCInstLowering, instead of generating the single precision
instructions during instruction selection or Prolog/Epilog code insertion.
Without the changes made in this patch, llc produces code that has the same
problem described in r137484 or bails out when
MipsInstrInfo::storeRegToStackSlot or loadRegFromStackSlot is called before
register allocation.
llvm-svn: 137711
Craig Topper