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
44 lines
1.3 KiB
LLVM
44 lines
1.3 KiB
LLVM
; RUN: llvm-dis < %s.bc | FileCheck %s --check-prefixes=CHECK,CHECK-TYPED
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; callbr.ll.bc was generated by passing this file to llvm-as.
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; RUN: llvm-as < %s | llvm-dis | FileCheck %s --check-prefixes=CHECK,CHECK-TYPED
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; RUN: llvm-as -opaque-pointers < %s | llvm-dis -opaque-pointers | FileCheck %s --check-prefixes=CHECK,CHECK-OPAQUE
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define i32 @test_asm_goto(i32 %x){
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entry:
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; CHECK: callbr void asm "", "r,!i"(i32 %x)
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; CHECK-NEXT: to label %normal [label %fail]
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callbr void asm "", "r,!i"(i32 %x) to label %normal [label %fail]
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normal:
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ret i32 1
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fail:
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ret i32 0
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}
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define i32 @test_asm_goto2(i32 %x){
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entry:
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; CHECK: callbr void asm "", "r,!i,!i"(i32 %x)
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; CHECK-NEXT: to label %normal [label %fail, label %fail2]
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callbr void asm "", "r,!i,!i"(i32 %x) to label %normal [label %fail, label %fail2]
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normal:
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ret i32 1
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fail:
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ret i32 0
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fail2:
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ret i32 2
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}
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define i32 @test_asm_goto3(i32 %x){
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entry:
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; CHECK-TYPED: callbr void asm "", "r,i,!i"(i32 %x, i8* blockaddress(@test_asm_goto3, %unrelated))
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; CHECK-OPAQUE: callbr void asm "", "r,i,!i"(i32 %x, ptr blockaddress(@test_asm_goto3, %unrelated))
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; CHECK-NEXT: to label %normal [label %fail]
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callbr void asm "", "r,i,!i"(i32 %x, i8* blockaddress(@test_asm_goto3, %unrelated)) to label %normal [label %fail]
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normal:
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ret i32 1
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fail:
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ret i32 0
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unrelated:
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ret i32 2
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}
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