[llvm] r239915 - Add documentation for new backedge mass propagation in irregular loops.
Diego Novillo
dnovillo at google.com
Wed Jun 17 09:28:22 PDT 2015
Author: dnovillo
Date: Wed Jun 17 11:28:22 2015
New Revision: 239915
URL: http://llvm.org/viewvc/llvm-project?rev=239915&view=rev
Log:
Add documentation for new backedge mass propagation in irregular loops.
Tweak test cases and rename headerIndexFor -> getHeaderIndex.
Removed:
llvm/trunk/test/Analysis/BlockFrequencyInfo/PR23525.ll
Modified:
llvm/trunk/include/llvm/Analysis/BlockFrequencyInfoImpl.h
llvm/trunk/lib/Analysis/BlockFrequencyInfoImpl.cpp
llvm/trunk/test/Analysis/BlockFrequencyInfo/irreducible.ll
Modified: llvm/trunk/include/llvm/Analysis/BlockFrequencyInfoImpl.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/BlockFrequencyInfoImpl.h?rev=239915&r1=239914&r2=239915&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/BlockFrequencyInfoImpl.h (original)
+++ llvm/trunk/include/llvm/Analysis/BlockFrequencyInfoImpl.h Wed Jun 17 11:28:22 2015
@@ -226,7 +226,7 @@ public:
BlockNode getHeader() const { return Nodes[0]; }
bool isIrreducible() const { return NumHeaders > 1; }
- HeaderMassList::difference_type headerIndexFor(const BlockNode &B) {
+ HeaderMassList::difference_type getHeaderIndex(const BlockNode &B) {
assert(isHeader(B) && "this is only valid on loop header blocks");
if (isIrreducible())
return std::lower_bound(Nodes.begin(), Nodes.begin() + NumHeaders, B) -
@@ -716,6 +716,17 @@ void IrreducibleGraph::addEdges(const Bl
/// - Distribute the mass accordingly, dithering to minimize mass loss,
/// as described in \a distributeMass().
///
+/// In the case of irreducible loops, instead of a single loop header,
+/// there will be several. The computation of backedge masses is similar
+/// but instead of having a single backedge mass, there will be one
+/// backedge per loop header. In these cases, each backedge will carry
+/// a mass proportional to the edge weights along the corresponding
+/// path.
+///
+/// At the end of propagation, the full mass assigned to the loop will be
+/// distributed among the loop headers proportionally according to the
+/// mass flowing through their backedges.
+///
/// Finally, calculate the loop scale from the accumulated backedge mass.
///
/// 3. Distribute mass in the function (\a computeMassInFunction()).
Modified: llvm/trunk/lib/Analysis/BlockFrequencyInfoImpl.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BlockFrequencyInfoImpl.cpp?rev=239915&r1=239914&r2=239915&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BlockFrequencyInfoImpl.cpp (original)
+++ llvm/trunk/lib/Analysis/BlockFrequencyInfoImpl.cpp Wed Jun 17 11:28:22 2015
@@ -414,8 +414,7 @@ void BlockFrequencyInfoImplBase::distrib
// Check for a backedge.
if (W.Type == Weight::Backedge) {
- auto ix = OuterLoop->headerIndexFor(W.TargetNode);
- OuterLoop->BackedgeMass[ix] += Taken;
+ OuterLoop->BackedgeMass[OuterLoop->getHeaderIndex(W.TargetNode)] += Taken;
DEBUG(debugAssign(*this, D, W.TargetNode, Taken, "back"));
continue;
}
@@ -741,7 +740,7 @@ void BlockFrequencyInfoImplBase::adjustL
DEBUG(dbgs() << "adjust-loop-header-mass:\n");
for (uint32_t H = 0; H < Loop.NumHeaders; ++H) {
auto &HeaderNode = Loop.Nodes[H];
- auto &BackedgeMass = Loop.BackedgeMass[Loop.headerIndexFor(HeaderNode)];
+ auto &BackedgeMass = Loop.BackedgeMass[Loop.getHeaderIndex(HeaderNode)];
DEBUG(dbgs() << " - Add back edge mass for node "
<< getBlockName(HeaderNode) << ": " << BackedgeMass << "\n");
Dist.addLocal(HeaderNode, BackedgeMass.getMass());
Removed: llvm/trunk/test/Analysis/BlockFrequencyInfo/PR23525.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BlockFrequencyInfo/PR23525.ll?rev=239914&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/BlockFrequencyInfo/PR23525.ll (original)
+++ llvm/trunk/test/Analysis/BlockFrequencyInfo/PR23525.ll (removed)
@@ -1,80 +0,0 @@
-; RUN: opt < %s -analyze -block-freq | FileCheck %s
-
- at g = global i32 0, align 4
-
-; Function Attrs: inlinehint noinline nounwind uwtable
-define i32 @_Z8hot_loopi(i32 %n) !prof !1 {
-entry:
- %div = sdiv i32 %n, 2
- %rem12 = and i32 %n, 1
- %cmp = icmp eq i32 %rem12, 0
- br i1 %cmp, label %Next, label %for.cond, !prof !2
-
-; CHECK: - for.cond: float = 25.85{{[0-9]*}}, int = 206
-for.cond: ; preds = %entry, %for.inc
- %i.0 = phi i32 [ %inc, %for.inc ], [ %div, %entry ]
- %cmp1 = icmp slt i32 %i.0, %n
- br i1 %cmp1, label %for.body, label %for.end, !prof !3, !llvm.loop !4
-
-; CHECK: - for.body: float = 24.52, int = 196
-for.body: ; preds = %for.cond
- %rem213 = and i32 %i.0, 1
- %cmp3 = icmp eq i32 %rem213, 0
- br i1 %cmp3, label %if.then.4, label %Next, !prof !6
-
-; CHECK: - if.then.4: float = 12.26{{[0-9]*}}, int = 98
-if.then.4: ; preds = %for.body
- %0 = load i32, i32* @g, align 4, !tbaa !7
- %mul = shl nsw i32 %0, 1
- br label %for.inc
-
-; CHECK: - Next: float = 12.41{{[0-9]*}}, int = 99
-Next: ; preds = %for.body, %entry
- %i.1 = phi i32 [ %div, %entry ], [ %i.0, %for.body ]
- %1 = load i32, i32* @g, align 4, !tbaa !7
- %add = add nsw i32 %1, %n
- br label %for.inc
-
-; CHECK: - for.inc: float = 38.28{{[0-9]*}}, int = 306
-for.inc: ; preds = %if.then.4, %Next
- %storemerge = phi i32 [ %add, %Next ], [ %mul, %if.then.4 ]
- %i.2 = phi i32 [ %i.1, %Next ], [ %i.0, %if.then.4 ]
- store i32 %storemerge, i32* @g, align 4, !tbaa !7
- %inc = add nsw i32 %i.2, 1
- br label %for.cond
-
-; CHECK: - for.end: float = 1.0, int = 8
-for.end: ; preds = %for.cond
- %2 = load i32, i32* @g, align 4, !tbaa !7
- ret i32 %2
-}
-
-; Function Attrs: nounwind uwtable
-define i32 @main() !prof !11 {
-entry:
- br label %for.body
-
-for.cond.cleanup: ; preds = %for.body
- ret i32 0
-
-for.body: ; preds = %for.body, %entry
- %i.04 = phi i32 [ 1, %entry ], [ %inc, %for.body ]
- %call = tail call i32 @_Z8hot_loopi(i32 %i.04)
- %inc = add nuw nsw i32 %i.04, 1
- %exitcond = icmp eq i32 %inc, 100
- br i1 %exitcond, label %for.cond.cleanup, label %for.body, !prof !12
-}
-
-
-!1 = !{!"function_entry_count", i64 99}
-!2 = !{!"branch_weights", i32 50, i32 51}
-!3 = !{!"branch_weights", i32 2452, i32 100}
-!4 = distinct !{!4, !5}
-!5 = !{!"llvm.loop.unroll.disable"}
-!6 = !{!"branch_weights", i32 1227, i32 1226}
-!7 = !{!8, !8, i64 0}
-!8 = !{!"int", !9, i64 0}
-!9 = !{!"omnipotent char", !10, i64 0}
-!10 = !{!"Simple C/C++ TBAA"}
-!11 = !{!"function_entry_count", i64 1}
-!12 = !{!"branch_weights", i32 2, i32 100}
Modified: llvm/trunk/test/Analysis/BlockFrequencyInfo/irreducible.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BlockFrequencyInfo/irreducible.ll?rev=239915&r1=239914&r2=239915&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/BlockFrequencyInfo/irreducible.ll (original)
+++ llvm/trunk/test/Analysis/BlockFrequencyInfo/irreducible.ll Wed Jun 17 11:28:22 2015
@@ -392,15 +392,15 @@ entry:
br i1 %x, label %left, label %right, !prof !21
left:
-; CHECK-NEXT: left: float = 0.14{{[0-9]*}},
+; CHECK-NEXT: left: float = 0.14
br i1 %x, label %top, label %bottom, !prof !22
right:
-; CHECK-NEXT: right: float = 0.42{{[0-9]*}},
+; CHECK-NEXT: right: float = 0.42
br i1 %x, label %top, label %bottom, !prof !22
top:
-; CHECK-NEXT: top: float = 8.43{{[0-9]*}},
+; CHECK-NEXT: top: float = 8.43
switch i2 %y, label %exit [ i2 0, label %left
i2 1, label %right
i2 2, label %bottom ], !prof !23
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