llvm-6502/test/Transforms/SampleProfile/propagate.ll

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Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/propagate.prof | opt -analyze -branch-prob | FileCheck %s
; Original C++ code for this test case:
;
; #include <stdio.h>
;
; long foo(int x, int y, long N) {
; if (x < y) {
; return y - x;
; } else {
; for (long i = 0; i < N; i++) {
; if (i > N / 3)
; x--;
; if (i > N / 4) {
; y++;
; x += 3;
; } else {
; for (unsigned j = 0; j < i; j++) {
; x += j;
; y -= 3;
; }
; }
; }
; }
; return y * x;
; }
;
; int main() {
; int x = 5678;
; int y = 1234;
; long N = 999999;
; printf("foo(%d, %d, %ld) = %ld\n", x, y, N, foo(x, y, N));
; return 0;
; }
; ModuleID = 'propagate.cc'
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@.str = private unnamed_addr constant [24 x i8] c"foo(%d, %d, %ld) = %ld\0A\00", align 1
; Function Attrs: nounwind uwtable
define i64 @_Z3fooiil(i32 %x, i32 %y, i64 %N) #0 {
entry:
%retval = alloca i64, align 8
%x.addr = alloca i32, align 4
%y.addr = alloca i32, align 4
%N.addr = alloca i64, align 8
%i = alloca i64, align 8
%j = alloca i32, align 4
store i32 %x, i32* %x.addr, align 4
store i32 %y, i32* %y.addr, align 4
store i64 %N, i64* %N.addr, align 8
%0 = load i32* %x.addr, align 4, !dbg !11
%1 = load i32* %y.addr, align 4, !dbg !11
%cmp = icmp slt i32 %0, %1, !dbg !11
br i1 %cmp, label %if.then, label %if.else, !dbg !11
if.then: ; preds = %entry
%2 = load i32* %y.addr, align 4, !dbg !13
%3 = load i32* %x.addr, align 4, !dbg !13
%sub = sub nsw i32 %2, %3, !dbg !13
%conv = sext i32 %sub to i64, !dbg !13
store i64 %conv, i64* %retval, !dbg !13
br label %return, !dbg !13
if.else: ; preds = %entry
store i64 0, i64* %i, align 8, !dbg !15
br label %for.cond, !dbg !15
for.cond: ; preds = %for.inc16, %if.else
%4 = load i64* %i, align 8, !dbg !15
%5 = load i64* %N.addr, align 8, !dbg !15
%cmp1 = icmp slt i64 %4, %5, !dbg !15
br i1 %cmp1, label %for.body, label %for.end18, !dbg !15
; CHECK: edge for.cond -> for.body probability is 10 / 11 = 90.9091% [HOT edge]
; CHECK: edge for.cond -> for.end18 probability is 1 / 11 = 9.09091%
for.body: ; preds = %for.cond
%6 = load i64* %i, align 8, !dbg !18
%7 = load i64* %N.addr, align 8, !dbg !18
%div = sdiv i64 %7, 3, !dbg !18
%cmp2 = icmp sgt i64 %6, %div, !dbg !18
br i1 %cmp2, label %if.then3, label %if.end, !dbg !18
; CHECK: edge for.body -> if.then3 probability is 1 / 5 = 20%
; CHECK: edge for.body -> if.end probability is 4 / 5 = 80%
if.then3: ; preds = %for.body
%8 = load i32* %x.addr, align 4, !dbg !21
%dec = add nsw i32 %8, -1, !dbg !21
store i32 %dec, i32* %x.addr, align 4, !dbg !21
br label %if.end, !dbg !21
if.end: ; preds = %if.then3, %for.body
%9 = load i64* %i, align 8, !dbg !22
%10 = load i64* %N.addr, align 8, !dbg !22
%div4 = sdiv i64 %10, 4, !dbg !22
%cmp5 = icmp sgt i64 %9, %div4, !dbg !22
br i1 %cmp5, label %if.then6, label %if.else7, !dbg !22
; CHECK: edge if.end -> if.then6 probability is 3 / 6342 = 0.0473037%
; CHECK: edge if.end -> if.else7 probability is 6339 / 6342 = 99.9527% [HOT edge]
if.then6: ; preds = %if.end
%11 = load i32* %y.addr, align 4, !dbg !24
%inc = add nsw i32 %11, 1, !dbg !24
store i32 %inc, i32* %y.addr, align 4, !dbg !24
%12 = load i32* %x.addr, align 4, !dbg !26
%add = add nsw i32 %12, 3, !dbg !26
store i32 %add, i32* %x.addr, align 4, !dbg !26
br label %if.end15, !dbg !27
if.else7: ; preds = %if.end
store i32 0, i32* %j, align 4, !dbg !28
br label %for.cond8, !dbg !28
for.cond8: ; preds = %for.inc, %if.else7
%13 = load i32* %j, align 4, !dbg !28
%conv9 = zext i32 %13 to i64, !dbg !28
%14 = load i64* %i, align 8, !dbg !28
%cmp10 = icmp slt i64 %conv9, %14, !dbg !28
br i1 %cmp10, label %for.body11, label %for.end, !dbg !28
; CHECK: edge for.cond8 -> for.body11 probability is 16191 / 16192 = 99.9938% [HOT edge]
; CHECK: edge for.cond8 -> for.end probability is 1 / 16192 = 0.00617589%
for.body11: ; preds = %for.cond8
%15 = load i32* %j, align 4, !dbg !31
%16 = load i32* %x.addr, align 4, !dbg !31
%add12 = add i32 %16, %15, !dbg !31
store i32 %add12, i32* %x.addr, align 4, !dbg !31
%17 = load i32* %y.addr, align 4, !dbg !33
%sub13 = sub nsw i32 %17, 3, !dbg !33
store i32 %sub13, i32* %y.addr, align 4, !dbg !33
br label %for.inc, !dbg !34
for.inc: ; preds = %for.body11
%18 = load i32* %j, align 4, !dbg !28
%inc14 = add i32 %18, 1, !dbg !28
store i32 %inc14, i32* %j, align 4, !dbg !28
br label %for.cond8, !dbg !28
for.end: ; preds = %for.cond8
br label %if.end15
if.end15: ; preds = %for.end, %if.then6
br label %for.inc16, !dbg !35
for.inc16: ; preds = %if.end15
%19 = load i64* %i, align 8, !dbg !15
%inc17 = add nsw i64 %19, 1, !dbg !15
store i64 %inc17, i64* %i, align 8, !dbg !15
br label %for.cond, !dbg !15
for.end18: ; preds = %for.cond
br label %if.end19
if.end19: ; preds = %for.end18
%20 = load i32* %y.addr, align 4, !dbg !36
%21 = load i32* %x.addr, align 4, !dbg !36
%mul = mul nsw i32 %20, %21, !dbg !36
%conv20 = sext i32 %mul to i64, !dbg !36
store i64 %conv20, i64* %retval, !dbg !36
br label %return, !dbg !36
return: ; preds = %if.end19, %if.then
%22 = load i64* %retval, !dbg !37
ret i64 %22, !dbg !37
}
; Function Attrs: uwtable
define i32 @main() #1 {
entry:
%retval = alloca i32, align 4
%x = alloca i32, align 4
%y = alloca i32, align 4
%N = alloca i64, align 8
store i32 0, i32* %retval
store i32 5678, i32* %x, align 4, !dbg !38
store i32 1234, i32* %y, align 4, !dbg !39
store i64 999999, i64* %N, align 8, !dbg !40
%0 = load i32* %x, align 4, !dbg !41
%1 = load i32* %y, align 4, !dbg !41
%2 = load i64* %N, align 8, !dbg !41
%3 = load i32* %x, align 4, !dbg !41
%4 = load i32* %y, align 4, !dbg !41
%5 = load i64* %N, align 8, !dbg !41
%call = call i64 @_Z3fooiil(i32 %3, i32 %4, i64 %5), !dbg !41
%call1 = call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([24 x i8]* @.str, i32 0, i32 0), i32 %0, i32 %1, i64 %2, i64 %call), !dbg !41
ret i32 0, !dbg !42
}
declare i32 @printf(i8*, ...) #2
attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!8, !9}
!llvm.ident = !{!10}
!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.5 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [propagate.cc] [DW_LANG_C_plus_plus]
!1 = metadata !{metadata !"propagate.cc", metadata !"."}
!2 = metadata !{i32 0}
!3 = metadata !{metadata !4, metadata !7}
!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"foo", metadata !"foo", metadata !"", i32 3, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i64 (i32, i32, i64)* @_Z3fooiil, null, null, metadata !2, i32 3} ; [ DW_TAG_subprogram ] [line 3] [def] [foo]
!5 = metadata !{i32 786473, metadata !1} ; [ DW_TAG_file_type ] [propagate.cc]
!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
!7 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"main", metadata !"main", metadata !"", i32 24, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 ()* @main, null, null, metadata !2, i32 24} ; [ DW_TAG_subprogram ] [line 24] [def] [main]
!8 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
!9 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
!10 = metadata !{metadata !"clang version 3.5 "}
!11 = metadata !{i32 4, i32 0, metadata !12, null}
!12 = metadata !{i32 786443, metadata !1, metadata !4, i32 4, i32 0, i32 0, i32 0} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
!13 = metadata !{i32 5, i32 0, metadata !14, null}
!14 = metadata !{i32 786443, metadata !1, metadata !12, i32 4, i32 0, i32 0, i32 1} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
!15 = metadata !{i32 7, i32 0, metadata !16, null}
!16 = metadata !{i32 786443, metadata !1, metadata !17, i32 7, i32 0, i32 0, i32 3} ; [ DW_TAG_lexical_block ] [propagate.cc]
!17 = metadata !{i32 786443, metadata !1, metadata !12, i32 6, i32 0, i32 0, i32 2} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
!18 = metadata !{i32 8, i32 0, metadata !19, null} ; [ DW_TAG_imported_declaration ]
!19 = metadata !{i32 786443, metadata !1, metadata !20, i32 8, i32 0, i32 0, i32 5} ; [ DW_TAG_lexical_block ] [propagate.cc]
!20 = metadata !{i32 786443, metadata !1, metadata !16, i32 7, i32 0, i32 0, i32 4} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
!21 = metadata !{i32 9, i32 0, metadata !19, null}
!22 = metadata !{i32 10, i32 0, metadata !23, null}
!23 = metadata !{i32 786443, metadata !1, metadata !20, i32 10, i32 0, i32 0, i32 6} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
!24 = metadata !{i32 11, i32 0, metadata !25, null}
!25 = metadata !{i32 786443, metadata !1, metadata !23, i32 10, i32 0, i32 0, i32 7} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
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!29 = metadata !{i32 786443, metadata !1, metadata !30, i32 14, i32 0, i32 0, i32 9} ; [ DW_TAG_lexical_block ] [propagate.cc]
!30 = metadata !{i32 786443, metadata !1, metadata !23, i32 13, i32 0, i32 0, i32 8} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
!31 = metadata !{i32 15, i32 0, metadata !32, null}
!32 = metadata !{i32 786443, metadata !1, metadata !29, i32 14, i32 0, i32 0, i32 10} ; [ DW_TAG_lexical_block ] [propagate.cc]
Propagation of profile samples through the CFG. This adds a propagation heuristic to convert instruction samples into branch weights. It implements a similar heuristic to the one implemented by Dehao Chen on GCC. The propagation proceeds in 3 phases: 1- Assignment of block weights. All the basic blocks in the function are initial assigned the same weight as their most frequently executed instruction. 2- Creation of equivalence classes. Since samples may be missing from blocks, we can fill in the gaps by setting the weights of all the blocks in the same equivalence class to the same weight. To compute the concept of equivalence, we use dominance and loop information. Two blocks B1 and B2 are in the same equivalence class if B1 dominates B2, B2 post-dominates B1 and both are in the same loop. 3- Propagation of block weights into edges. This uses a simple propagation heuristic. The following rules are applied to every block B in the CFG: - If B has a single predecessor/successor, then the weight of that edge is the weight of the block. - If all the edges are known except one, and the weight of the block is already known, the weight of the unknown edge will be the weight of the block minus the sum of all the known edges. If the sum of all the known edges is larger than B's weight, we set the unknown edge weight to zero. - If there is a self-referential edge, and the weight of the block is known, the weight for that edge is set to the weight of the block minus the weight of the other incoming edges to that block (if known). Since this propagation is not guaranteed to finalize for every CFG, we only allow it to proceed for a limited number of iterations (controlled by -sample-profile-max-propagate-iterations). It currently uses the same GCC default of 100. Before propagation starts, the pass builds (for each block) a list of unique predecessors and successors. This is necessary to handle identical edges in multiway branches. Since we visit all blocks and all edges of the CFG, it is cleaner to build these lists once at the start of the pass. Finally, the patch fixes the computation of relative line locations. The profiler emits lines relative to the function header. To discover it, we traverse the compilation unit looking for the subprogram corresponding to the function. The line number of that subprogram is the line where the function begins. That becomes line zero for all the relative locations. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-10 23:23:46 +00:00
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