[PATCH] D34515: [ARM] Materialise some boolean values to avoid a branch

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

If you're seeing references to apsr, you aren't lowering ADDCARRY correctly.

ARMISD::ADDE has three operands; two integers, and apsr.  It has two results: an integer, and the resulting apsr.  If you're lowering ADDCARRY to ARMISD::ADDE, you actually need three operations: one to convert the boolean carry input to an apsr, one ARMISD::ADDE to perform the actual operation, and one operation to convert the result apsr to a boolean.  See LowerADDSUBCARRY for how the x86 backend does this.

(Afterwards, you use a target dagcombine to eliminate the redundant operations.)


https://reviews.llvm.org/D34515