http://llvm.org/bugs/show_bug.cgi?id=22751
Bug ID: 22751
Summary: AArch64: EON instruction not selected efficiently
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Backend: AArch64
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The following code snippet should produce an EON instruction in both A64 and
A32:
unsigned long
f(unsigned long a, unsigned long b, unsigned long c) {
return (a ^ ~(b << 4));
}
On A64 and A32, we get two instructions produced:
eor x8, x0, x1, lsl #4
mvn x0, x8
I think this is because SDAG canonicalises the expression into "~(a ^ b << 4)",
which we don't recognize as a pattern for EON.
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