Implement an optimization for == and != comparisons like this:
_Bool test2(int X, int Y) {
return &arr[X][Y] == arr;
}
instead of generating this:
bool %test2(int %X, int %Y) {
%tmp.3.idx = mul int %X, 160 ; <int> [#uses=1]
%tmp.3.idx1 = shl int %Y, ubyte 2 ; <int> [#uses=1]
%tmp.3.offs2 = sub int 0, %tmp.3.idx ; <int> [#uses=1]
%tmp.7 = seteq int %tmp.3.idx1, %tmp.3.offs2 ; <bool> [#uses=1]
ret bool %tmp.7
}
generate this:
bool %test2(int %X, int %Y) {
seteq int %X, 0 ; <bool>:0 [#uses=1]
seteq int %Y, 0 ; <bool>:1 [#uses=1]
%tmp.7 = and bool %0, %1 ; <bool> [#uses=1]
ret bool %tmp.7
}
This idiom occurs in C++ programs when iterating from begin() to end(),
in a vector or array. For example, we now compile this:
void test(int X, int Y) {
for (int *i = arr; i != arr+100; ++i)
foo(*i);
}
to this:
no_exit: ; preds = %entry, %no_exit
...
%exitcond = seteq uint %indvar.next, 100 ; <bool> [#uses=1]
br bool %exitcond, label %return, label %no_exit
instead of this:
no_exit: ; preds = %entry, %no_exit
...
%inc5 = getelementptr [100 x [40 x int]]* %arr, int 0, int 0, int %inc.rec ; <int*> [#uses=1]
%tmp.8 = seteq int* %inc5, getelementptr ([100 x [40 x int]]* %arr, int 0, int 100, int 0) ; <bool> [#uses=1]
%indvar.next = add uint %indvar, 1 ; <uint> [#uses=1]
br bool %tmp.8, label %return, label %no_exit
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19536 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed