| //@ compile-flags: -Copt-level=3 |
| // Test that `pow` can use a faster implementation when `base` is a |
| // known power of two |
| |
| #![crate_type = "lib"] |
| |
| // 2 ** n == 2 ** (1 * n) == 1 << (1 * n) |
| // CHECK-LABEL: @pow2 |
| #[no_mangle] |
| pub fn pow2(exp: u32) -> u32 { |
| // CHECK: %[[OVERFLOW:.+]] = icmp ult i32 %exp, 32 |
| // CHECK: %[[POW:.+]] = shl nuw i32 1, %exp |
| // CHECK: %[[RET:.+]] = select i1 %[[OVERFLOW]], i32 %[[POW]], i32 0 |
| // CHECK: ret i32 %[[RET]] |
| 2u32.pow(exp) |
| } |
| |
| // 4 ** n == 2 ** (2 * n) == 1 << (2 * n) |
| // CHECK-LABEL: @pow4 |
| #[no_mangle] |
| pub fn pow4(exp: u32) -> u32 { |
| // CHECK: %[[ICMP1:.+]] = icmp slt i32 %exp, 0 |
| // CHECK: %[[SHIFT_AMOUNT:.+]] = shl i32 %exp, 1 |
| // CHECK: %[[ICMP2:.+]] = icmp ult i32 %[[SHIFT_AMOUNT]], 32 |
| // CHECK: %[[POW:.+]] = shl nuw i32 1, %[[SHIFT_AMOUNT]] |
| // CHECK: %[[SEL:.+]] = select i1 %[[ICMP2]], i32 %[[POW]], i32 0 |
| // CHECK: %[[RET:.+]] = select i1 %[[ICMP1]], i32 0, i32 %[[SEL]] |
| // CHECK: ret i32 %[[RET]] |
| 4u32.pow(exp) |
| } |
| |
| // 16 ** n == 2 ** (4 * n) == 1 << (4 * n) |
| // CHECK-LABEL: @pow16 |
| #[no_mangle] |
| pub fn pow16(exp: u32) -> u32 { |
| // CHECK: %[[ICMP1:.+]] = icmp ugt i32 %exp, 1073741823 |
| // CHECK: %[[SHIFT_AMOUNT:.+]] = shl i32 %exp, 2 |
| // CHECK: %[[ICMP2:.+]] = icmp ult i32 %[[SHIFT_AMOUNT]], 32 |
| // CHECK: %[[POW:.+]] = shl nuw i32 1, %[[SHIFT_AMOUNT]] |
| // CHECK: %[[SEL:.+]] = select i1 %[[ICMP2]], i32 %[[POW]], i32 0 |
| // CHECK: %[[RET:.+]] = select i1 %[[ICMP1]], i32 0, i32 %[[SEL]] |
| // CHECK: ret i32 %[[RET]] |
| 16u32.pow(exp) |
| } |
| |
| // (-2) ** n == (-2) ** (1 * n) == 1 << (1 * n) |
| // CHECK-LABEL: @pow_minus_2 |
| #[no_mangle] |
| pub fn pow_minus_2(exp: u32) -> i32 { |
| // CHECK: %[[IS_ODD:.+]] = and i32 %exp, 1 |
| // CHECK: %[[IS_EVEN:.+]] = icmp eq i32 %[[IS_ODD]], 0 |
| // CHECK: %[[BASE:.+]] = select i1 %[[IS_EVEN]], i32 1, i32 -1 |
| // CHECK: %[[OVERFLOW:.+]] = icmp ult i32 %exp, 32 |
| // CHECK: %[[SHIFT:.+]] = shl i32 %[[BASE]], %exp |
| // CHECK: %[[RET:.+]] = select i1 %[[OVERFLOW]], i32 %[[SHIFT]], i32 0 |
| // CHECK: ret i32 %[[RET]] |
| (-2i32).pow(exp) |
| } |
