[PATCH] D57434: Optimize pow(X, 0.75) to sqrt(X) * sqrt(sqrt(X))

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

LG in principle.



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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:11852
     // pow(-inf, 0.25) = +inf; sqrt(sqrt(-inf)) =  NaN.
+    // pow(-0.0, 0.75) = +0.0; sqrt(-0.0) * sqrt(sqrt(-0.0)) = +0.0.
+    // pow(-inf, 0.75) = +inf; sqrt(-inf) * sqrt(sqrt(-inf)) =  NaN.
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Looks like this doesn't //need// to be guarded by `nsz` flag?


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Comment at: llvm/test/CodeGen/X86/pow.75.ll:2
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-- -debug 2>&1 | FileCheck %s
+
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Why `-debug`, instead of checking the asm?


Repository:
  rL LLVM

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  https://reviews.llvm.org/D57434/new/

https://reviews.llvm.org/D57434