something that reassoc doesn't think about yet.
-//===---------------------------------------------------------------------===//
-
-This function: (derived from GCC PR19988)
-double foo(double x, double y) {
- return ((x + 0.1234 * y) * (x + -0.1234 * y));
-}
-
-compiles to:
-_foo:
- movapd %xmm1, %xmm2
- mulsd LCPI1_1(%rip), %xmm1
- mulsd LCPI1_0(%rip), %xmm2
- addsd %xmm0, %xmm1
- addsd %xmm0, %xmm2
- movapd %xmm1, %xmm0
- mulsd %xmm2, %xmm0
- ret
-
-Reassociate should be able to turn it into:
-
-double foo(double x, double y) {
- return ((x + 0.1234 * y) * (x - 0.1234 * y));
-}
-
-Which allows the multiply by constant to be CSE'd, producing:
-
-_foo:
- mulsd LCPI1_0(%rip), %xmm1
- movapd %xmm1, %xmm2
- addsd %xmm0, %xmm2
- subsd %xmm1, %xmm0
- mulsd %xmm2, %xmm0
- ret
-
-This doesn't need -ffast-math support at all. This is particularly bad because
-the llvm-gcc frontend is canonicalizing the later into the former, but clang
-doesn't have this problem.
-
//===---------------------------------------------------------------------===//
These two functions should generate the same code on big-endian systems: