Details: https://reviews.llvm.org/D96805 changed the GCNTTIImpl::getCFInstrCost to return 1 for the PHI nodes
for the TTI::TCK_CodeSize and TTI::TCK_SizeAndLatency. This is incorrect because the value moves that are the
result of the PHI lowering are inserted into the basic block predecessors - not into the block itself.
As a result of this change LoopRotate and LoopUnroll were broken because of the incorrect Loop header and loop
body size/cost estimation.
Reviewed By: rampitec
Differential Revision: https://reviews.llvm.org/D105104
}
case Instruction::Ret:
return SCost ? 1 : 10;
- case Instruction::PHI:
- // TODO: 1. A prediction phi won't be eliminated?
- // 2. Estimate data copy instructions in this case.
- return 1;
}
return BaseT::getCFInstrCost(Opcode, CostKind, I);
}
; SPEED: estimated cost of 10 for instruction: ret void
; SIZE: estimated cost of 5 for instruction: br i1
; SIZE: estimated cost of 1 for instruction: br label
-; SIZE: estimated cost of 1 for instruction: %phi = phi i32 [
+; SIZE: estimated cost of 0 for instruction: %phi = phi i32 [
; SIZE: estimated cost of 1 for instruction: ret void
define amdgpu_kernel void @test_br_cost(i32 addrspace(1)* %out, i32 addrspace(1)* %vaddr, i32 %b) #0 {
bb0: