https://bugs.llvm.org/show_bug.cgi?id=41113
Bug ID: 41113
Summary: swap select operands and reuse existing inverted
condition
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: spatel+l...@rotateright.com
CC: llvm-bugs@lists.llvm.org
I'm not sure if there's an existing pass that should have responsibility for
this transform:
define i1 @swapportunity(i8 %a, i8 %b, i8 %c, i8 %d, i8* %p) {
%cmp1 = icmp ult i8 %a, %b
%sel = select i1 %cmp1, i8 %c, i8 %d
store i8 %sel, i8* %p
%cmp2 = icmp uge i8 %a, %b ; this could also be a 'not' of cmp1
ret i1 %cmp2
}
-->
define i1 @swapportunity(i8 %a, i8 %b, i8 %c, i8 %d, i8* %p) {
%cmp2 = icmp uge i8 %a, %b
%swap = select i1 %cmp2, i8 %d, i8 %c
store i8 %swap, i8* %p
ret i1 %cmp2
}
-------------------------------------------------------------------
It's not quite CSE or instcombine. There's precedence for a similar
analysis/transform in instcombine via "swapMayExposeCSEOpportunities()", but
that seems suspect to include there as this is not really a local/peephole
pattern-match.
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