Until AVX512DQ we only support i64/vXi64 sitofp conversion as scalars.
This patch sees if the sign bit extends far enough that we can truncate to a i32 type and then perform sitofp without loss of precision.
Differential Revision: https://reviews.llvm.org/D24345
llvm-svn: 281502
This patch helps avoid false dependencies on undef registers by updating the machine instructions' undef operand to use a register that the instruction is truly dependent on, or use a register with clearance higher than Pref.
Pseudo example:
loop:
xmm0 = ...
xmm1 = vcvtsi2sdl eax, xmm0<undef>
... = inst xmm0
jmp loop
In this example, selecting xmm0 as the undef register creates false dependency between loop iterations.
This false dependency cannot be solved by inserting an xor before vcvtsi2sdl because xmm0 is alive at the point of the vcvtsi2sdl instruction.
Selecting a different register instead of xmm0, especially a register that is not used in the loop, will eliminate this problem.
Differential Revision: https://reviews.llvm.org/D22466
llvm-svn: 278321
Simon Pilgrim