diff options
Diffstat (limited to 'test/codegen/mathbits.go')
| -rw-r--r-- | test/codegen/mathbits.go | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go index acc9930c61..b506a37006 100644 --- a/test/codegen/mathbits.go +++ b/test/codegen/mathbits.go @@ -620,6 +620,39 @@ func Add64MPanicOnOverflowGT(a, b [2]uint64) [2]uint64 { return r } +// Verify independent carry chain operations are scheduled efficiently +// and do not cause unnecessary save/restore of the CA bit. +// +// This is an example of why CarryChainTail priority must be lower +// (earlier in the block) than Memory. f[0]=f1 could be scheduled +// after the first two lower 64 bit limb adds, but before either +// high 64 bit limbs are added. +// +// This is what happened on PPC64 when compiling +// crypto/internal/edwards25519/field.feMulGeneric. +func Add64MultipleChains(a, b, c, d [2]uint64) { + var cx, d1, d2 uint64 + a1, a2 := a[0], a[1] + b1, b2 := b[0], b[1] + c1, c2 := c[0], c[1] + + // ppc64: "ADDC\tR\\d+,", -"ADDE", -"MOVD\tXER" + // ppc64le: "ADDC\tR\\d+,", -"ADDE", -"MOVD\tXER" + d1, cx = bits.Add64(a1, b1, 0) + // ppc64: "ADDE", -"ADDC", -"MOVD\t.*, XER" + // ppc64le: "ADDE", -"ADDC", -"MOVD\t.*, XER" + d2, _ = bits.Add64(a2, b2, cx) + + // ppc64: "ADDC\tR\\d+,", -"ADDE", -"MOVD\tXER" + // ppc64le: "ADDC\tR\\d+,", -"ADDE", -"MOVD\tXER" + d1, cx = bits.Add64(c1, d1, 0) + // ppc64: "ADDE", -"ADDC", -"MOVD\t.*, XER" + // ppc64le: "ADDE", -"ADDC", -"MOVD\t.*, XER" + d2, _ = bits.Add64(c2, d2, cx) + d[0] = d1 + d[1] = d2 +} + // --------------- // // bits.Sub* // // --------------- // |