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
55 lines
1.7 KiB
LLVM
55 lines
1.7 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
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; RUN: opt -callsite-splitting -S -o - < %s | FileCheck %s
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; Check that we can split the critical edge between Top and CallSiteBB, and
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; rewrite the first callbr's indirect destination correctly.
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define void @caller() {
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; CHECK-LABEL: define {{[^@]+}}@caller() {
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; CHECK-NEXT: Top:
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; CHECK-NEXT: callbr void asm sideeffect "", "!i,~{dirflag},~{fpsr},~{flags}"()
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; CHECK-NEXT: to label [[NEXTCOND:%.*]] [label %Top.split]
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; CHECK: Top.split:
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; CHECK-NEXT: call void @callee(i1 false)
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; CHECK-NEXT: br label [[CALLSITEBB:%.*]]
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; CHECK: NextCond:
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; CHECK-NEXT: br label [[NEXTCOND_SPLIT:%.*]]
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; CHECK: NextCond.split:
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; CHECK-NEXT: call void @callee(i1 true)
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; CHECK-NEXT: br label [[CALLSITEBB]]
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; CHECK: CallSiteBB:
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; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ false, [[TOP_SPLIT:%.*]] ], [ true, [[NEXTCOND_SPLIT]] ]
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; CHECK-NEXT: callbr void asm sideeffect "", "r,!i,~{dirflag},~{fpsr},~{flags}"(i1 [[PHI]])
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; CHECK-NEXT: to label [[END:%.*]] [label %End2]
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; CHECK: End:
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; CHECK-NEXT: ret void
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; CHECK: End2:
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; CHECK-NEXT: ret void
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;
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Top:
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callbr void asm sideeffect "", "!i,~{dirflag},~{fpsr},~{flags}"()
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to label %NextCond [label %CallSiteBB]
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NextCond:
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br label %CallSiteBB
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CallSiteBB:
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%phi = phi i1 [0, %Top],[1, %NextCond]
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call void @callee(i1 %phi)
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callbr void asm sideeffect "", "r,!i,~{dirflag},~{fpsr},~{flags}"(i1 %phi)
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to label %End [label %End2]
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End:
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ret void
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End2:
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ret void
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}
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define void @callee(i1 %b) {
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; CHECK-LABEL: define {{[^@]+}}@callee
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; CHECK-SAME: (i1 [[B:%.*]]) {
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; CHECK-NEXT: ret void
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;
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ret void
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}
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