https://bugs.llvm.org/show_bug.cgi?id=34753
Bug ID: 34753
Summary: [AArch64][CodeGen][CodeSize] Redundant 'and' can be
remove with shifts in addr mode
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: AArch64
Assignee: unassignedb...@nondot.org
Reporter: mcros...@codeaurora.org
CC: llvm-bugs@lists.llvm.org
Test case:
int test(unsigned long long a, unsigned long long b, int *table) {
return table[(a * b) >> 58];
}
Current assembly:
test: // @test
// BB#0: // %entry
mul x8, x1, x0
lsr x8, x8, #56
and x8, x8, #0xfc
ldr w0, [x2, x8]
ret
We should be able to remove the 'and' for a code size with as follows:
test: // @test
// BB#0: // %entry
mul x8, x1, x0
lsr x8, x8, #58
ldr w0, [x2, x8, lsl#2]
ret
I'm not interested in pursuing this optimization, but I figured I'd file the
bug, regardless.
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