0846e56e63
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 llvm-svn: 283934
101 lines
2.8 KiB
LLVM
101 lines
2.8 KiB
LLVM
; RUN: llc -outline-optional-branches -O2 < %s | FileCheck %s
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target datalayout = "e-m:e-i64:64-n32:64"
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target triple = "powerpc64le-grtev4-linux-gnu"
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; Intended layout:
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; The outlining flag produces the layout
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; test1
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; test2
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; test3
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; test4
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; exit
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; optional1
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; optional2
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; optional3
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; optional4
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; Tail duplication puts test n+1 at the end of optional n
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; so optional1 includes a copy of test2 at the end, and branches
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; to test3 (at the top) or falls through to optional 2.
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; The CHECK statements check for the whole string of tests and exit block,
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; and then check that the correct test has been duplicated into the end of
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; the optional blocks and that the optional blocks are in the correct order.
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;CHECK-LABEL: f:
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; test1 may have been merged with entry
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;CHECK: mr [[TAGREG:[0-9]+]], 3
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;CHECK: andi. {{[0-9]+}}, [[TAGREG]], 1
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;CHECK-NEXT: bc 12, 1, [[OPT1LABEL:[._0-9A-Za-z]+]]
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;CHECK-NEXT: [[TEST2LABEL:[._0-9A-Za-z]+]]: # %test2
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;CHECK-NEXT: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 30, 30
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;CHECK-NEXT: bne 0, [[OPT2LABEL:[._0-9A-Za-z]+]]
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;CHECK-NEXT: [[TEST3LABEL:[._0-9A-Za-z]+]]: # %test3
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;CHECK-NEXT: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 29, 29
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;CHECK-NEXT: bne 0, .[[OPT3LABEL:[._0-9A-Za-z]+]]
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;CHECK-NEXT: [[TEST4LABEL:[._0-9A-Za-z]+]]: # %test4
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;CHECK-NEXT: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 28, 28
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;CHECK-NEXT: bne 0, .[[OPT4LABEL:[._0-9A-Za-z]+]]
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;CHECK-NEXT: [[EXITLABEL:[._0-9A-Za-z]+]]: # %exit
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;CHECK: blr
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;CHECK-NEXT: [[OPT1LABEL]]
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;CHECK: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 30, 30
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;CHECK-NEXT: beq 0, [[TEST3LABEL]]
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;CHECK-NEXT: [[OPT2LABEL]]
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;CHECK: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 29, 29
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;CHECK-NEXT: beq 0, [[TEST4LABEL]]
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;CHECK-NEXT: [[OPT3LABEL]]
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;CHECK: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 28, 28
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;CHECK-NEXT: beq 0, [[EXITLABEL]]
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;CHECK-NEXT: [[OPT4LABEL]]
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;CHECK: b [[EXITLABEL]]
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define void @f(i32 %tag) {
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entry:
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br label %test1
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test1:
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%tagbit1 = and i32 %tag, 1
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%tagbit1eq0 = icmp eq i32 %tagbit1, 0
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br i1 %tagbit1eq0, label %test2, label %optional1
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optional1:
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call void @a()
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call void @a()
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call void @a()
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call void @a()
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br label %test2
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test2:
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%tagbit2 = and i32 %tag, 2
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%tagbit2eq0 = icmp eq i32 %tagbit2, 0
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br i1 %tagbit2eq0, label %test3, label %optional2
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optional2:
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call void @b()
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call void @b()
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call void @b()
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call void @b()
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br label %test3
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test3:
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%tagbit3 = and i32 %tag, 4
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%tagbit3eq0 = icmp eq i32 %tagbit3, 0
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br i1 %tagbit3eq0, label %test4, label %optional3
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optional3:
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call void @c()
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call void @c()
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call void @c()
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call void @c()
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br label %test4
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test4:
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%tagbit4 = and i32 %tag, 8
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%tagbit4eq0 = icmp eq i32 %tagbit4, 0
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br i1 %tagbit4eq0, label %exit, label %optional4
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optional4:
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call void @d()
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call void @d()
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call void @d()
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call void @d()
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br label %exit
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exit:
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ret void
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}
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declare void @a()
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declare void @b()
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declare void @c()
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declare void @d()
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