[GlobalISel] Allow some load/store instructions to be folded in Match Table backend #70830
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… Table backend Load/store instruction can be folded into non-adjacent instruction within the same basic block, if there are no other instructions with memory/other side effects between them.
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@llvm/pr-subscribers-llvm-globalisel Author: Vladislav Dzhidzhoev (dzhidzhoev) ChangesLoad/store instruction can be folded into non-adjacent instruction Full diff: https://github.com/llvm/llvm-project/pull/70830.diff 1 Files Affected:
diff --git a/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp b/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp
index 26752369a7711a1..3441df8a342e4f1 100644
--- a/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp
@@ -70,6 +70,25 @@ bool GIMatchTableExecutor::isObviouslySafeToFold(MachineInstr &MI,
if (MI.isConvergent() && MI.getParent() != IntoMI.getParent())
return false;
- return !MI.mayLoadOrStore() && !MI.mayRaiseFPException() &&
- !MI.hasUnmodeledSideEffects() && MI.implicit_operands().empty();
+ auto IsSafe = [](const MachineInstr &MI) {
+ return !MI.mayRaiseFPException() && !MI.hasUnmodeledSideEffects() &&
+ MI.implicit_operands().empty();
+ };
+ auto IsSafeNoMem = [IsSafe](const MachineInstr &MI) {
+ return !MI.mayLoadOrStore() && IsSafe(MI);
+ };
+
+ // If source instruction uses memory, fold if no intermediate
+ // instructions use it.
+ if (MI.mayLoadOrStore() && IsSafe(MI) &&
+ MI.getParent() == IntoMI.getParent()) {
+ auto IntoIt = IntoMI.getIterator();
+ auto NextIt = std::next(MI.getIterator());
+ while (!NextIt.isEnd() && NextIt != IntoIt && IsSafeNoMem(*NextIt))
+ ++NextIt;
+ if (NextIt == IntoIt)
+ return true;
+ }
+
+ return IsSafeNoMem(MI);
}
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arsenm
reviewed
Nov 1, 2023
| !MI.hasUnmodeledSideEffects() && MI.implicit_operands().empty(); | ||
| auto IsSafe = [](const MachineInstr &MI) { | ||
| return !MI.mayRaiseFPException() && !MI.hasUnmodeledSideEffects() && | ||
| MI.implicit_operands().empty(); |
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Don't understand the implicit operands check. I think this is starting to reproduce MachineInstr::isSafeToMove
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reverse ping? |
arsenm
requested changes
Feb 6, 2024
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arsenm
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arsenm
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Seems to be reinventing isSafeToMove
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Implemented in #101675. |
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Load/store instruction can be folded into non-adjacent instruction
within the same basic block, if there are no other instructions with
memory/other side effects between them.