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llvm-6502/test/Transforms/InstSimplify/2010-12-20-Distribute.ll
Duncan Sands fe02c69f84 Simplify (X<<1)-X into X. According to my auto-simplier this is the most common missed
simplification in fully optimized code.  It occurs sporadically in the testsuite, and
many times in 403.gcc: the final bitcode has 131 fewer subtractions after this change.
The reason that the multiplies are not eliminated is the same reason that instcombine
did not catch this: they are used by other instructions (instcombine catches this with
a more general transform which in general is only profitable if the operands have only
one use).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123754 91177308-0d34-0410-b5e6-96231b3b80d8
2011-01-18 09:24:58 +00:00

63 lines
1.2 KiB
LLVM

; RUN: opt < %s -instsimplify -S | FileCheck %s
define i32 @factorize(i32 %x, i32 %y) {
; CHECK: @factorize
; (X | 1) & (X | 2) -> X | (1 & 2) -> X
%l = or i32 %x, 1
%r = or i32 %x, 2
%z = and i32 %l, %r
ret i32 %z
; CHECK: ret i32 %x
}
define i32 @factorize2(i32 %x) {
; CHECK: @factorize2
; 3*X - 2*X -> X
%l = mul i32 3, %x
%r = mul i32 2, %x
%z = sub i32 %l, %r
ret i32 %z
; CHECK: ret i32 %x
}
define i32 @factorize3(i32 %x, i32 %a, i32 %b) {
; CHECK: @factorize3
; (X | (A|B)) & (X | B) -> X | ((A|B) & B) -> X | B
%aORb = or i32 %a, %b
%l = or i32 %x, %aORb
%r = or i32 %x, %b
%z = and i32 %l, %r
ret i32 %z
; CHECK: ret i32 %r
}
define i32 @factorize4(i32 %x, i32 %y) {
; CHECK: @factorize4
%sh = shl i32 %y, 1
%ml = mul i32 %sh, %x
%mr = mul i32 %x, %y
%s = sub i32 %ml, %mr
ret i32 %s
; CHECK: ret i32 %mr
}
define i32 @factorize5(i32 %x, i32 %y) {
; CHECK: @factorize5
%sh = mul i32 %y, 2
%ml = mul i32 %sh, %x
%mr = mul i32 %x, %y
%s = sub i32 %ml, %mr
ret i32 %s
; CHECK: ret i32 %mr
}
define i32 @expand(i32 %x) {
; CHECK: @expand
; ((X & 1) | 2) & 1 -> ((X & 1) & 1) | (2 & 1) -> (X & 1) | 0 -> X & 1
%a = and i32 %x, 1
%b = or i32 %a, 2
%c = and i32 %b, 1
ret i32 %c
; CHECK: ret i32 %a
}