[PATCH] D57121: [ARM] Use sub for negative offset load/store in thumb1

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

Can you give an example where this transform helps for ldrsb/ldrsh?



================
Comment at: lib/Target/ARM/ARMISelDAGToDAG.cpp:1043
+  if (auto C = dyn_cast<ConstantSDNode>(N.getOperand(1)))
+    return C->getSExtValue() < 0;
+
----------------
Does the actual value matter here?  If we're going to generate a constant pool load, this doesn't seem profitable.


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  https://reviews.llvm.org/D57121/new/

https://reviews.llvm.org/D57121