[PATCH] D29872: Do not legalize large add with addc/adde, introduce addcarry and do it with uaddo/addcarry

[Amaury SECHET via Phabricator via llvm-commits]

deadalnix added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp:516
   EVT ValueVTs[] = { N->getValueType(0), NVT };
-  SDValue Ops[] = { N->getOperand(0), N->getOperand(1) };
+  SDValue Ops[3] = { N->getOperand(0), N->getOperand(1) };
+  auto C = N->getNumOperands();
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zvi wrote:
> Consider using a SmallVector here.
The can only be 2 or 3 element so i think just allocating for 2 on the stack is preferable. This is done in various other places in the codebase already.


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Comment at: lib/Target/X86/X86ISelLowering.cpp:23103
+
+  // Let legalize expand this if it isn't a legal type yet.
+  if (!DAG.getTargetLoweringInfo().isTypeLegal(VT))
----------------
zvi wrote:
> I know this also appears at the top of LowerADDC_ADDE_SUBC_SUBE, but why it this check needed?
Because in that case, the backend wants to run some extra legalization code before coming back there.


https://reviews.llvm.org/D29872