2a721374ae
Following some recent discussions, this changes the representation
of callbrs in IR. The current blockaddress arguments are replaced
with `!` label constraints that refer directly to callbr indirect
destinations:
; Before:
%res = callbr i8* asm "", "=r,r,i"(i8* %x, i8* blockaddress(@test8, %foo))
to label %asm.fallthrough [label %foo]
; After:
%res = callbr i8* asm "", "=r,r,!i"(i8* %x)
to label %asm.fallthrough [label %foo]
The benefit of this is that we can easily update the successors of
a callbr, without having to worry about also updating blockaddress
references. This should allow us to remove some limitations:
* Allow unrolling/peeling/rotation of callbr, or any other
clone-based optimizations
(https://github.com/llvm/llvm-project/issues/41834)
* Allow duplicate successors
(https://github.com/llvm/llvm-project/issues/45248)
This is just the IR representation change though, I will follow up
with patches to remove limtations in various transformation passes
that are no longer needed.
Differential Revision: https://reviews.llvm.org/D129288
32 lines
523 B
LLVM
32 lines
523 B
LLVM
; RUN: llvm-diff %s %s
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define void @foo() {
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entry:
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callbr void asm sideeffect "", "!i,!i,~{dirflag},~{fpsr},~{flags}"()
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to label %asm.fallthrough [label %return, label %t_no]
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asm.fallthrough:
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br label %return
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t_no:
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br label %return
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return:
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ret void
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}
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define void @bar() {
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entry:
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callbr void asm sideeffect "", "!i,!i,~{dirflag},~{fpsr},~{flags}"()
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to label %asm.fallthrough [label %return, label %t_no]
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asm.fallthrough:
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br label %return
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t_no:
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br label %return
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return:
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ret void
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}
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