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An instruction may define part of a register where the other bits are undefined. In that case, it is safe to rematerialize the instruction. For example: %vreg2:ssub_0<def> = VLDRS <cp#0>, 0, pred:14, pred:%noreg, %vreg2<imp-def> The extra <imp-def> operand indicates that the instruction does not read the other parts of the virtual register, so a remat is safe. This patch simply allows multiple def operands for the virtual register. It is MI->readsVirtualRegister() that determines if we depend on a previous value so remat is impossible. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138953 91177308-0d34-0410-b5e6-96231b3b80d8
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