[X86][BtVer2] Remove wrong ReadAdvance from AVX vbroadcast(ss|sd|f128) instructions.
The presence of a ReadAdvance for input operand #0 is problematic
because it changes the input latency of the register used as the base address
for the folded load.
A broadcast cannot start executing if the load address hasn't been computed yet.
In the llvm-mca example, the VBROADCASTSS is dependent on the address generated
by the LEAQ. That means, it cannot start until LEAQ reaches the write-back
stage. If we apply ReadAdvance, then we wrongly assume that the load can start 3
cycles in advance.
Differential Revision: https://reviews.llvm.org/D51534
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341222
91177308-0d34-0410-b5e6-
96231b3b80d8
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