assigned to @lattner

Compile this with llvm-gcc:

unsigned int *a, *b;

void joy(void) {
a[20] = ((a[10]|b[10]) | (a[10]&b[10]));
}

and you get:

define void @​joy() {
entry:
%tmp = load i32** @​a ; <i32*> [#uses=2]
%tmp2 = getelementptr i32* %tmp, i32 10 ; <i32*> [#uses=1]
%tmp3 = load i32* %tmp2 ; [#uses=2]
%tmp4 = load i32** @​b ; <i32*> [#uses=1]
%tmp5 = getelementptr i32* %tmp4, i32 10 ; <i32*> [#uses=1]
%tmp6 = load i32* %tmp5 ; [#uses=2]
%tmp7 = or i32 %tmp6, %tmp3 ; [#uses=1]
%tmp7not = xor i32 %tmp7, -1 ; [#uses=1]
%tmp14 = and i32 %tmp6, %tmp3 ; [#uses=1]
%tmp15 = or i32 %tmp14, %tmp7not ; [#uses=1]
%tmp15not = xor i32 %tmp15, -1 ; [#uses=1]
%tmp16 = getelementptr i32* %tmp, i32 20 ; <i32*> [#uses=1]
store i32 %tmp15not, i32* %tmp16
ret void
}

it could just use xor?

this module is really just doing an xor

Here's a C vector example:

typedef unsigned attribute((vector_size(16))) vu;

vu test1(vu a, vu b) {
return ((a|b) | (a&b));
}

vu test2(vu a, vu b) {
return (a|b) & ~(a&b);
}

Implemented. There are many patches to this, the primary ones being:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070611/050487.html
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070611/050489.html
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070611/050495.html

Testcase here: Transforms/InstCombine/and-or-not.ll

This shrunk Duraid's nasty example from 32K lines of x86-64 .s file to 23k lines.

-Chris