https://bugs.llvm.org/show_bug.cgi?id=34887
Bug ID: 34887
Summary: [CodeGen][ExpandMemcmp] Regression on memcmp(p1, p2,
N) lowering for N={16,32} (X86)
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Common Code Generator Code
Assignee: unassignedb...@nondot.org
Reporter: clement.cour...@gmail.com
CC: llvm-bugs@lists.llvm.org
When memcmp expansion was enabled in CodeGenPrepare, there was a regression for
N=16 at least on X86.
Before enabling CodeGen/ExpandMemcmp, a memcmp(x, y, 16)
would be expanded by SelectionDAGBuilder::visitMemCmpCall into vector
loads + compares.
When CodeGen/ExpandMemcmp was enabled, the 16 byte memcmp would be
expanded to two 8-byte load and compares, preventing
SelectionDAGBuilder::visitMemCmpCall to do its job later.
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