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Author SHA1 Message Date
Chad Rosier
ef01edf1e9 The Neon VCVT (between floating-point and fixed-point, Advanced SIMD)
instructions can be used to match combinations of multiply/divide and VCVT 
(between floating-point and integer, Advanced SIMD).  Basically the VCVT 
immediate operand that specifies the number of fraction bits corresponds to a 
floating-point multiply or divide by the corresponding power of 2.

For example, VCVT (floating-point to fixed-point, Advanced SIMD) can replace a 
combination of VMUL and VCVT (floating-point to integer) as follows:

Example (assume d17 = <float 8.000000e+00, float 8.000000e+00>):
  vmul.f32        d16, d17, d16
  vcvt.s32.f32    d16, d16
becomes:
  vcvt.s32.f32    d16, d16, #3

Similarly, VCVT (fixed-point to floating-point, Advanced SIMD) can replace a 
combinations of VCVT (integer to floating-point) and VDIV as follows:

Example (assume d17 = <float 8.000000e+00, float 8.000000e+00>):
  vcvt.f32.s32    d16, d16
  vdiv.f32        d16, d17, d16
becomes:
  vcvt.f32.s32    d16, d16, #3

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133813 91177308-0d34-0410-b5e6-96231b3b80d8
2011-06-24 19:23:04 +00:00