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Hiroshi Yamauchi 0596ae1e4a Add heuristics for irreducible loop metadata under PGO
Summary:
Add the following heuristics for irreducible loop metadata:

- When an irreducible loop header is missing the loop header weight metadata,
  give it the minimum weight seen among other headers.
- Annotate indirectbr targets with the loop header weight metadata (as they are
  likely to become irreducible loop headers after indirectbr tail duplication.)

These greatly improve the accuracy of the block frequency info of the Python
interpreter loop (eg. from ~3-16x off down to ~40-55% off) and the Python
performance (eg. unpack_sequence from ~50% slower to ~8% faster than GCC) due to
better register allocation under PGO.

Reviewers: davidxl

Reviewed By: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39980

llvm-svn: 318693
2017-11-20 21:03:38 +00:00

140 lines
5.7 KiB
LLVM

; RUN: llvm-profdata merge %S/Inputs/irreducible.proftext -o %t.profdata
; RUN: opt < %s -pgo-instr-use -pgo-test-profile-file=%t.profdata -S | FileCheck %s --check-prefix=USE
; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -S | FileCheck %s --check-prefix=USE
; GEN: $__llvm_profile_raw_version = comdat any
; Function Attrs: noinline norecurse nounwind readnone uwtable
define i32 @_Z11irreducibleii(i32 %iter_outer, i32 %iter_inner) local_unnamed_addr #0 {
entry:
%cmp24 = icmp sgt i32 %iter_outer, 0
br i1 %cmp24, label %for.body, label %entry.for.cond.cleanup_crit_edge
entry.for.cond.cleanup_crit_edge: ; preds = %entry
br label %for.cond.cleanup
for.cond.cleanup: ; preds = %entry.for.cond.cleanup_crit_edge, %for.end
%sum.0.lcssa = phi i32 [ 0, %entry.for.cond.cleanup_crit_edge ], [ %sum.1, %for.end ]
ret i32 %sum.0.lcssa
for.body: ; preds = %entry, %for.end
%k.026 = phi i32 [ %inc12, %for.end ], [ 0, %entry ]
%sum.025 = phi i32 [ %sum.1, %for.end ], [ 0, %entry ]
%rem23 = and i32 %k.026, 1
%cmp1 = icmp eq i32 %rem23, 0
br i1 %cmp1, label %entry8, label %for.cond2
for.cond2: ; preds = %for.body, %if.end9
%sum.1 = phi i32 [ %add10, %if.end9 ], [ %sum.025, %for.body ]
%i.0 = phi i32 [ %inc, %if.end9 ], [ 0, %for.body ]
%cmp3 = icmp slt i32 %i.0, %iter_inner
br i1 %cmp3, label %for.body4, label %for.end
; USE: br i1 %cmp3, label %for.body4, label %for.end, !prof !{{[0-9]+}},
; USE-SAME: !irr_loop ![[FOR_COND2_IRR_LOOP:[0-9]+]]
for.body4: ; preds = %for.cond2
%rem5 = srem i32 %k.026, 3
%cmp6 = icmp eq i32 %rem5, 0
br i1 %cmp6, label %entry8, label %if.end9
entry8: ; preds = %for.body4, %for.body
%sum.2 = phi i32 [ %sum.025, %for.body ], [ %sum.1, %for.body4 ]
%i.1 = phi i32 [ 0, %for.body ], [ %i.0, %for.body4 ]
%add = add nsw i32 %sum.2, 4
br label %if.end9
; USE: br label %if.end9,
; USE-SAME: !irr_loop ![[ENTRY8_IRR_LOOP:[0-9]+]]
if.end9: ; preds = %entry8, %for.body4
%sum.3 = phi i32 [ %add, %entry8 ], [ %sum.1, %for.body4 ]
%i.2 = phi i32 [ %i.1, %entry8 ], [ %i.0, %for.body4 ]
%add10 = add nsw i32 %sum.3, 1
%inc = add nsw i32 %i.2, 1
br label %for.cond2
; USE: br label %for.cond2,
; USE-SAME: !irr_loop ![[IF_END9_IRR_LOOP:[0-9]+]]
for.end: ; preds = %for.cond2
%inc12 = add nuw nsw i32 %k.026, 1
%exitcond = icmp eq i32 %inc12, %iter_outer
br i1 %exitcond, label %for.cond.cleanup, label %for.body
}
@targets = local_unnamed_addr global [256 x i8*] zeroinitializer, align 16
@tracing = local_unnamed_addr global i32 0, align 4
; Function Attrs: noinline norecurse nounwind uwtable
define i32 @_Z11irreduciblePh(i8* nocapture readonly %p) {
entry:
%0 = load i32, i32* @tracing, align 4
%1 = trunc i32 %0 to i8
%tobool = icmp eq i32 %0, 0
br label %for.cond1
for.cond1: ; preds = %sw.default, %entry
br label %dispatch_op
dispatch_op: ; preds = %sw.bb6, %for.cond1
switch i8 %1, label %sw.default [
i8 0, label %sw.bb
i8 1, label %dispatch_op.sw.bb6_crit_edge
i8 2, label %sw.bb15
]
dispatch_op.sw.bb6_crit_edge: ; preds = %dispatch_op
br label %sw.bb6
sw.bb: ; preds = %indirectgoto, %dispatch_op
br label %exit
TARGET_1: ; preds = %indirectgoto
br label %sw.bb6
; USE: br label %sw.bb6, !irr_loop {{.*}}
sw.bb6: ; preds = %TARGET_1, %dispatch_op.sw.bb6_crit_edge
br i1 %tobool, label %dispatch_op, label %if.then
; USE: br i1 %tobool, label %dispatch_op, label %if.then, !prof !{{[0-9]+}},
; USE-SAME: !irr_loop ![[SW_BB6_IRR_LOOP:[0-9]+]]
if.then: ; preds = %sw.bb6
br label %indirectgoto
TARGET_2: ; preds = %indirectgoto
br label %sw.bb15
; USE: br label %sw.bb15, !irr_loop {{.*}}
sw.bb15: ; preds = %TARGET_2, %dispatch_op
br i1 %tobool, label %if.then18, label %exit
; USE: br i1 %tobool, label %if.then18, label %exit, !prof !{{[0-9]+}},
; USE-SAME: !irr_loop ![[SW_BB15_IRR_LOOP:[0-9]+]]
if.then18: ; preds = %sw.bb15
br label %indirectgoto
unknown_op: ; preds = %indirectgoto
br label %sw.default
sw.default: ; preds = %unknown_op, %dispatch_op
br label %for.cond1
exit: ; preds = %sw.bb15, %sw.bb
ret i32 0
indirectgoto: ; preds = %if.then18, %if.then
%idxprom21 = zext i32 %0 to i64
%arrayidx22 = getelementptr inbounds [256 x i8*], [256 x i8*]* @targets, i64 0, i64 %idxprom21
%target = load i8*, i8** %arrayidx22, align 8
indirectbr i8* %target, [label %unknown_op, label %sw.bb, label %TARGET_1, label %TARGET_2]
; USE: indirectbr i8* %target, [label %unknown_op, label %sw.bb, label %TARGET_1, label %TARGET_2], !prof !{{[0-9]+}},
; USE-SAME: !irr_loop ![[INDIRECTGOTO_IRR_LOOP:[0-9]+]]
}
; USE: ![[FOR_COND2_IRR_LOOP]] = !{!"loop_header_weight", i64 1050}
; USE: ![[ENTRY8_IRR_LOOP]] = !{!"loop_header_weight", i64 373}
; USE: ![[IF_END9_IRR_LOOP]] = !{!"loop_header_weight", i64 1000}
; USE: ![[SW_BB6_IRR_LOOP]] = !{!"loop_header_weight", i64 501}
; USE: ![[SW_BB15_IRR_LOOP]] = !{!"loop_header_weight", i64 100}
; USE: ![[INDIRECTGOTO_IRR_LOOP]] = !{!"loop_header_weight", i64 400}