https://bugs.llvm.org/show_bug.cgi?id=42631
Bug ID: 42631
Summary: Transform (1 << (x+1)) to (2 << x)
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: david.bolvan...@gmail.com
CC: llvm-bugs@lists.llvm.org
%a = add nuw i32 %x, 1
%r = shl i32 1, %a
=>
%r = shl i32 2, %x
Done: 1
Optimization is correct!
int v1(unsigned x) {
return (2 << x);
}
int v2(unsigned x) {
return (1 << (x+1));
}
v1: # @v1
mov ecx, edi
mov eax, 2
shl eax, cl
ret
v2: # @v2
lea ecx, [rdi + 1]
mov eax, 1
shl eax, cl
ret
Worth to do? Opinions?
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