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Note switch-lowering inefficiency.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107565 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1888,3 +1888,39 @@ of the ADD, and replacing the ADD with the ADDE, should give the desired result.
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(That said, we are doing a lot better than gcc on this testcase. :) )
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//===---------------------------------------------------------------------===//
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Switch lowering generates less than ideal code for the following switch:
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define void @a(i32 %x) nounwind {
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entry:
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switch i32 %x, label %if.end [
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i32 0, label %if.then
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i32 1, label %if.then
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i32 2, label %if.then
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i32 3, label %if.then
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i32 5, label %if.then
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]
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if.then:
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tail call void @foo() nounwind
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ret void
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if.end:
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ret void
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}
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declare void @foo()
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Generated code on x86-64 (other platforms give similar results):
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a:
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cmpl $5, %edi
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ja .LBB0_2
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movl %edi, %eax
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movl $47, %ecx
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btq %rax, %rcx
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jb .LBB0_3
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.LBB0_2:
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ret
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.LBB0_3:
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xorb %al, %al
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jmp foo@PLT # TAILCALL
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The movl+movl+btq+jb could be simplified to a cmpl+jne.
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//===---------------------------------------------------------------------===//
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