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| author | pvanhout <pierre.vanhoutryve@amd.com> | 2023-06-26 17:59:55 +0200 |
|---|---|---|
| committer | pvanhout <pierre.vanhoutryve@amd.com> | 2023-06-29 15:12:27 +0200 |
| commit | c59f9eada1abe369c0470aa2dad8b20ac5269020 (patch) | |
| tree | eda8e2fdece60b024c1714f62ddc36f08bb77105 /llvm/lib/CodeGen/MachineCopyPropagation.cpp | |
| parent | 5e87ec1e19ce0226ff7c812db07aec1734c407b3 (diff) | |
| download | llvm-c59f9eada1abe369c0470aa2dad8b20ac5269020.zip llvm-c59f9eada1abe369c0470aa2dad8b20ac5269020.tar.gz llvm-c59f9eada1abe369c0470aa2dad8b20ac5269020.tar.bz2 | |
[MCP] Optimize copies from undef
Revert D152502 and instead optimize away copy from undefs, but clear the undef flag on the original copy.
Apparently, not optimizing the COPY can cause performance issues in some cases.
Fixes SWDEV-405813, SWDEV-405899
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D153838
Diffstat (limited to 'llvm/lib/CodeGen/MachineCopyPropagation.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/MachineCopyPropagation.cpp | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp index 26110a1..3453e6c 100644 --- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp +++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp @@ -462,8 +462,7 @@ bool MachineCopyPropagation::eraseIfRedundant(MachineInstr &Copy, auto PrevCopyOperands = isCopyInstr(*PrevCopy, *TII, UseCopyInstr); // Check that the existing copy uses the correct sub registers. - if (PrevCopyOperands->Destination->isDead() || - PrevCopyOperands->Source->isUndef()) + if (PrevCopyOperands->Destination->isDead()) return false; if (!isNopCopy(*PrevCopy, Src, Def, TRI, TII, UseCopyInstr)) return false; @@ -482,6 +481,12 @@ bool MachineCopyPropagation::eraseIfRedundant(MachineInstr &Copy, make_range(PrevCopy->getIterator(), Copy.getIterator())) MI.clearRegisterKills(CopyDef, TRI); + // Clear undef flag from remaining copy if needed. + if (!CopyOperands->Source->isUndef()) { + PrevCopy->getOperand(PrevCopyOperands->Source->getOperandNo()) + .setIsUndef(false); + } + Copy.eraseFromParent(); Changed = true; ++NumDeletes; |