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
16 lines
355 B
LLVM
16 lines
355 B
LLVM
; Test that asm goto can be compiled.
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;
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; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14
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define i32 @c() {
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entry:
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callbr void asm sideeffect "j d", "!i"()
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to label %asm.fallthrough [label %d]
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asm.fallthrough: ; preds = %entry
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br label %d
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d: ; preds = %asm.fallthrough, %entry
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ret i32 undef
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}
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