https://bugs.llvm.org/show_bug.cgi?id=39455
Bug ID: 39455
Summary: Simplify repeated bounds checks to a min/max reduction
style pattern
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Common Code Generator Code
Assignee: unassignedb...@nondot.org
Reporter: llvm-...@redking.me.uk
CC: llvm-bugs@lists.llvm.org, spatel+l...@rotateright.com
Checking multiple variables against the same value might be more efficiently
performed as just checking the maximum of the variables:
#include <algorithm>
bool foo(int f, int g) { return f < 123 && g < 123; }
bool bar(int f, int g) { return std::max(f, g) < 123; }
The or case might be similarly handled:
#include <algorithm>
bool foo(int f, int g) { return f < 123 || g < 123; }
bool bar(int f, int g) { return std::min(f, g) < 123; }
The higher the number of variables the higher the likelihood that its
performant (a full vector reduction pattern might even be worthwhile).
Float types might benefit similarly (or more as fmin/fmax instructions are more
common).
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