Summary:
Also fixup rL371928 for cases that occur on our out-of-tree backend
There were still quite a few intermediate APInts and this caused the
compile time of MCCodeEmitter for our target to jump from 16s up to
~5m40s. This patch, brings it back down to ~17s by eliminating pretty
much all of them using two new APInt functions (extractBitsAsZExtValue(),
insertBits() but with a uint64_t). The exact conditions for eliminating
them is that the field extracted/inserted must be <=64-bit which is
almost always true.
Note: The two new APInt API's assume that APInt::WordSize is at least
64-bit because that means they touch at most 2 APInt words. They
statically assert that's true. It seems very unlikely that someone
is patching it to be smaller so this should be fine.
Reviewers: jmolloy
Reviewed By: jmolloy
Subscribers: hiraditya, dexonsmith, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67686
llvm-svn: 372243
Some VLIW instruction sets are Very Long Indeed. Using uint64_t constricts the Inst encoding to 64 bits (naturally).
This change switches CodeEmitter to a mode that uses APInts when Inst's bitwidth is > 64 bits (NFC for existing targets).
When Inst.BitWidth > 64 the prototype changes to:
void TargetMCCodeEmitter::getBinaryCodeForInstr(const MCInst &MI,
SmallVectorImpl<MCFixup> &Fixups,
APInt &Inst,
APInt &Scratch,
const MCSubtargetInfo &STI);
The Inst parameter returns the encoded instruction, the Scratch parameter is used internally for manipulating operands and is exposed so that the underlying storage can be reused between calls to getBinaryCodeForInstr. The goal is to elide any APInt constructions that we can.
Similarly the operand encoding prototype changes to:
getMachineOpValue(const MCInst &MI, const MCOperand &MO, APInt &op, SmallVectorImpl<MCFixup> &Fixups, const MCSubtargetInfo &STI);
That is, the operand is passed by reference as APInt rather than returned as uint64_t.
To reiterate, this APInt mode is enabled only when Inst.BitWidth > 64, so this change is NFC for existing targets.
llvm-svn: 371928
Paul C. Anagnostopoulos