[PATCH] D120597: [RISCV] With Zbb, fold (sext_inreg (abs X)) -> (max X, (negw X))

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: llvm/test/CodeGen/RISCV/rv64zbb.ll:977
 ; RV64ZBB-NEXT:    max a0, a0, a1
-; RV64ZBB-NEXT:    sext.w a0, a0
 ; RV64ZBB-NEXT:    ret
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achieveartificialintelligence wrote:
> If line 964 `(i32 signext %x)` takes effect, why can't we remove line 977 directly?
The absolute value of a 32-bit value is a 33-bit number because 0xffffffff80000000 becomes 0x0000000080000000. The sign extend at the end will change it back to 0xffffffff80000000.


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  https://reviews.llvm.org/D120597/new/

https://reviews.llvm.org/D120597