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2a18018c10
The tail duplication pass uses an assumed layout when making duplication decisions. This is fine, but passes up duplication opportunities that may arise when blocks are outlined. Because we want the updated CFG to affect subsequent placement decisions, this change must occur during placement. In order to achieve this goal, TailDuplicationPass is split into a utility class, TailDuplicator, and the pass itself. The pass delegates nearly everything to the TailDuplicator object, except for looping over the blocks in a function. This allows the same code to be used for tail duplication in both places. This change, in concert with outlining optional branches, allows triangle shaped code to perform much better, esepecially when the taken/untaken branches are correlated, as it creates a second spine when the tests are small enough. Issue from previous rollback fixed, and a new test was added for that case as well. Issue was worklist/scheduling/taildup issue in layout. Issue from 2nd rollback fixed, with 2 additional tests. Issue was tail merging/loop info/tail-duplication causing issue with loops that share a header block. Issue with early tail-duplication of blocks that branch to a fallthrough predecessor fixed with test case: tail-dup-branch-to-fallthrough.ll Differential revision: https://reviews.llvm.org/D18226 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283934 91177308-0d34-0410-b5e6-96231b3b80d8
80 lines
1.8 KiB
YAML
80 lines
1.8 KiB
YAML
# RUN: llc -march=x86-64 -verify-machineinstrs -run-pass block-placement -o - %s | FileCheck %s
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# Check the conditional jump in bb.1 is changed to unconditional after block placement swaps bb.2 and bb.3.
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--- |
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@a = external global i16
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@b = external global i32
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declare void @dummy1()
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declare void @dummy2()
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declare void @dummy3()
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; Function Attrs: nounwind
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define void @f2() {
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br i1 undef, label %bb1, label %bb3
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bb1:
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call void @dummy1()
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call void @dummy1()
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call void @dummy1()
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br i1 undef, label %bb2, label %bb2
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bb2:
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call void @dummy2()
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call void @dummy2()
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call void @dummy2()
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br label %bb4
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bb3:
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call void @dummy3()
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call void @dummy3()
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call void @dummy3()
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br label %bb2
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bb4:
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ret void
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}
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...
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---
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# CHECK-LABEL: name: f2
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# CHECK: bb.1:
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# CHECK: JMP_1 %bb.2
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# CHECK: bb.3:
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# CHECK: bb.2:
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name: f2
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body: |
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bb.0 (%ir-block.0):
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successors: %bb.1(50), %bb.3(50)
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JNE_1 %bb.1, implicit %eflags
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JMP_1 %bb.3
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bb.1:
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successors: %bb.2(100)
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CALL64pcrel32 @dummy1, csr_64, implicit %rsp, implicit-def %rsp
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CALL64pcrel32 @dummy1, csr_64, implicit %rsp, implicit-def %rsp
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CALL64pcrel32 @dummy1, csr_64, implicit %rsp, implicit-def %rsp
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JNE_1 %bb.2, implicit %eflags
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bb.2:
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successors: %bb.4(100)
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CALL64pcrel32 @dummy2, csr_64, implicit %rsp, implicit-def %rsp
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CALL64pcrel32 @dummy2, csr_64, implicit %rsp, implicit-def %rsp
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CALL64pcrel32 @dummy2, csr_64, implicit %rsp, implicit-def %rsp
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JMP_1 %bb.4
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bb.3:
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successors: %bb.2(100)
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CALL64pcrel32 @dummy3, csr_64, implicit %rsp, implicit-def %rsp
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CALL64pcrel32 @dummy3, csr_64, implicit %rsp, implicit-def %rsp
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CALL64pcrel32 @dummy3, csr_64, implicit %rsp, implicit-def %rsp
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JMP_1 %bb.2
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bb.4:
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RETQ
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...
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