[PATCH] D38378: [ARM] Optimize {s,u}{add,sub}.with.overflow.
Roger Ferrer Ibanez via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 14 00:08:06 PST 2017
rogfer01 added inline comments.
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Comment at: lib/Target/ARM/ARMBaseInstrInfo.cpp:2677-2679
// One is MI, the other is a SUB instruction.
// For CMPrr(r1,r2), we are looking for SUB(r1,r2) or SUB(r2,r1).
// For CMPri(r1, CmpValue), we are looking for SUBri(r1, CmpValue).
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Maybe I'm reading it wrong: should this comment say something like `the other is a SUB or ADD instruction`?
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Comment at: lib/Target/ARM/ARMBaseInstrInfo.cpp:2741-2745
+ // Check whether CmpInstr can be made redundant by the current instruction.
+ if (isRedundantFlagInstr(&CmpInstr, SrcReg, SrcReg2, CmpValue, &*I)) {
+ SubAdd = &*I;
+ break;
+ }
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It is not clear to me why you had to swap this check with the one below? Is it related to the `--E;` in line 2731?
https://reviews.llvm.org/D38378
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