http://llvm.org/bugs/show_bug.cgi?id=12461
Bug #: 12461
Summary: clang does not optimize some recursive function
Product: clang
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: -New Bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
Given the function
int sum(int d)
{
if (d == 99999) return 1;
return !d ? 0 : (d + sum(d-1));
}
clang does not generate loopified code at any optimization level, while gcc
does at -O2 and above. returning 0 instead if 1 for d == 99999 lets clang
optimize the function properly.
gcc also folds evaluations of that function with arguments not too large, while
clang does not. Even in the "return 0" case, clang only inlines the function
instead evaluating it at compile time - but that's just minor.
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