diff options
| -rw-r--r-- | lib/Target/README.txt | 33 |
1 files changed, 30 insertions, 3 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 1f982b7f76..695fcc8fa8 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -198,11 +198,11 @@ Scalar Repl cannot currently promote this testcase to 'ret long cst': %struct.Y = type { %struct.X } ulong %bar() { %retval = alloca %struct.Y, align 8 ; <%struct.Y*> [#uses=3] - %tmp12 = getelementptr %struct.Y* %retval, int 0, uint 0, uint 0 ; <int*> [#uses=1] + %tmp12 = getelementptr %struct.Y* %retval, int 0, uint 0, uint 0 store int 0, int* %tmp12 - %tmp15 = getelementptr %struct.Y* %retval, int 0, uint 0, uint 1 ; <int*> [#uses=1] + %tmp15 = getelementptr %struct.Y* %retval, int 0, uint 0, uint 1 store int 1, int* %tmp15 - %retval = cast %struct.Y* %retval to ulong* ; <ulong*> [#uses=1] + %retval = cast %struct.Y* %retval to ulong* %retval = load ulong* %retval ; <ulong> [#uses=1] ret ulong %retval } @@ -247,3 +247,30 @@ Legalize should lower ctlz like this: on targets that have popcnt but not ctlz. itanium, what else? +//===---------------------------------------------------------------------===// + +quantum_sigma_x in 462.libquantum contains the following loop: + + for(i=0; i<reg->size; i++) + { + /* Flip the target bit of each basis state */ + reg->node[i].state ^= ((MAX_UNSIGNED) 1 << target); + } + +Where MAX_UNSIGNED/state is a 64-bit int. On a 32-bit platform it would be just +so cool to turn it into something like: + + if (target < 32) { + for(i=0; i<reg->size; i++) + reg->node[i].state ^= ((int) (1 << target)); + } else { + for(i=0; i<reg->size; i++) + reg->node[i].state ^= (long long)((int) (1 << (target-32))) << 32; + } + +... which would only do one 32-bit XOR per loop iteration instead of two. + +It would also be nice to recognize the reg->size doesn't alias reg->node[i], but +alas... + +//===---------------------------------------------------------------------===// |