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[LCSSA] Handle case with single new PHI faster.
If there is only a single available value, all uses must be dominated by
the single value and there is no need to search for a reaching
definition.
This drastically speeds up LCSSA in some cases. For the test case
from PR37202, it speeds up LCSSA construction by 4 times.
Time-passes without this patch for test case from PR37202:
Total Execution Time: 29.9285 seconds (29.9276 wall clock)
---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name ---
5.2786 ( 17.7%) 0.0021 ( 1.2%) 5.2806 ( 17.6%) 5.2808 ( 17.6%) Unswitch loops
4.3739 ( 14.7%) 0.0303 ( 18.1%) 4.4042 ( 14.7%) 4.4042 ( 14.7%) Loop-Closed SSA Form Pass
4.2658 ( 14.3%) 0.0192 ( 11.5%) 4.2850 ( 14.3%) 4.2851 ( 14.3%) Loop-Closed SSA Form Pass #2
2.2307 ( 7.5%) 0.0013 ( 0.8%) 2.2320 ( 7.5%) 2.2318 ( 7.5%) Loop Invariant Code Motion
2.0888 ( 7.0%) 0.0012 ( 0.7%) 2.0900 ( 7.0%) 2.0897 ( 7.0%) Unroll loops
1.6761 ( 5.6%) 0.0013 ( 0.8%) 1.6774 ( 5.6%) 1.6774 ( 5.6%) Value Propagation
1.3686 ( 4.6%) 0.0029 ( 1.8%) 1.3716 ( 4.6%) 1.3714 ( 4.6%) Induction Variable Simplification
1.1457 ( 3.8%) 0.0010 ( 0.6%) 1.1468 ( 3.8%) 1.1468 ( 3.8%) Loop-Closed SSA Form Pass #4
1.1384 ( 3.8%) 0.0005 ( 0.3%) 1.1389 ( 3.8%) 1.1389 ( 3.8%) Loop-Closed SSA Form Pass #6
1.1360 ( 3.8%) 0.0027 ( 1.6%) 1.1387 ( 3.8%) 1.1387 ( 3.8%) Loop-Closed SSA Form Pass #5
1.1331 ( 3.8%) 0.0010 ( 0.6%) 1.1341 ( 3.8%) 1.1340 ( 3.8%) Loop-Closed SSA Form Pass #3
Time passes with this patch
Total Execution Time: 19.2802 seconds (19.2813 wall clock)
---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name ---
4.4234 ( 23.2%) 0.0038 ( 2.0%) 4.4272 ( 23.0%) 4.4273 ( 23.0%) Unswitch loops
2.3828 ( 12.5%) 0.0020 ( 1.1%) 2.3848 ( 12.4%) 2.3847 ( 12.4%) Unroll loops
1.8714 ( 9.8%) 0.0020 ( 1.1%) 1.8734 ( 9.7%) 1.8735 ( 9.7%) Loop Invariant Code Motion
1.7973 ( 9.4%) 0.0022 ( 1.2%) 1.7995 ( 9.3%) 1.8003 ( 9.3%) Value Propagation
1.4010 ( 7.3%) 0.0033 ( 1.8%) 1.4043 ( 7.3%) 1.4044 ( 7.3%) Induction Variable Simplification
0.9978 ( 5.2%) 0.0244 ( 13.1%) 1.0222 ( 5.3%) 1.0224 ( 5.3%) Loop-Closed SSA Form Pass #2
0.9611 ( 5.0%) 0.0257 ( 13.8%) 0.9868 ( 5.1%) 0.9868 ( 5.1%) Loop-Closed SSA Form Pass
0.5856 ( 3.1%) 0.0015 ( 0.8%) 0.5871 ( 3.0%) 0.5869 ( 3.0%) Unroll loops #2
0.4132 ( 2.2%) 0.0012 ( 0.7%) 0.4145 ( 2.1%) 0.4143 ( 2.1%) Loop Invariant Code Motion #3
Reviewers: efriedma, davide, mzolotukhin
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D57033
llvm-svn: 352960
This commit is contained in:
Florian Hahn
parent
042546c4fa
commit
f4f72b46f9
@ -197,6 +197,17 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
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continue;
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}
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// If we added a single PHI, it must dominate all uses and we can directly
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// rename it.
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if (AddedPHIs.size() == 1) {
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// Tell the VHs that the uses changed. This updates SCEV's caches.
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// We might call ValueIsRAUWd multiple times for the same value.
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if (UseToRewrite->get()->hasValueHandle())
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ValueHandleBase::ValueIsRAUWd(*UseToRewrite, AddedPHIs[0]);
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UseToRewrite->set(AddedPHIs[0]);
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continue;
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}
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// Otherwise, do full PHI insertion.
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SSAUpdate.RewriteUse(*UseToRewrite);
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}
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@ -210,9 +221,12 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
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BasicBlock *UserBB = DVI->getParent();
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if (InstBB == UserBB || L->contains(UserBB))
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continue;
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// We currently only handle debug values residing in blocks where we have
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// inserted a PHI instruction.
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if (Value *V = SSAUpdate.FindValueForBlock(UserBB))
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// We currently only handle debug values residing in blocks that were
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// traversed while rewriting the uses. If we inserted just a single PHI,
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// we will handle all relevant debug values.
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Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
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: SSAUpdate.FindValueForBlock(UserBB);
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if (V)
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DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
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}
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@ -1,54 +1,118 @@
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; RUN: opt -S -lcssa < %s | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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; Reproducer for PR39019.
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;
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; Verify that the llvm.dbg.value in the %for.cond.cleanup2 block is rewritten
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; to use the PHI node for %add that is created by LCSSA.
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; Verify that the llvm.dbg.values are updated to use the PHI nodes inserted by
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; LCSSA.
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; CHECK-LABEL: for.cond.cleanup2:
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; CHECK-NEXT: [[PN:%[^ ]*]] = phi i32 [ %add.lcssa, %for.cond.cleanup1 ]
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[PN]], metadata [[VAR:![0-9]+]], metadata !DIExpression())
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; For the test case @single_exit, we can rewrite all llvm.dbg.value calls
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; to use the inserted PHI.
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; CHECK-LABEL: @single_exit(
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; CHECK-LABEL: inner.body:
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; CHECK: %add = add nsw i32 0, 2
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; CHECK: call void @llvm.dbg.value(metadata i32 %add, metadata [[VAR:![0-9]+]], metadata !DIExpression())
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; CHECK-LABEL: outer.exit:
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; CHECK-NEXT: [[PN:%[^ ]*]] = phi i32 [ %add.lcssa, %outer.latch ]
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[PN]], metadata [[VAR]], metadata !DIExpression())
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; CHECK-NEXT: call void @bar(i32 [[PN]])
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; CHECK-LABEL: for.body:
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; CHECK: %add = add nsw i32 0, 2
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; CHECK: call void @llvm.dbg.value(metadata i32 %add, metadata [[VAR]], metadata !DIExpression())
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; CHECK-LABEL: exit:
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[PN]], metadata [[VAR]], metadata !DIExpression())
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; CHECK: [[VAR]] = !DILocalVariable(name: "sum",
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; Function Attrs: nounwind
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define void @foo() #0 !dbg !6 {
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define void @single_exit() !dbg !6 {
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entry:
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br label %for.cond.preheader, !dbg !12
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br label %outer.header, !dbg !12
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for.cond.preheader: ; preds = %for.cond.cleanup1, %entry
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br label %for.body, !dbg !12
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outer.header: ; preds = %outer.latch, %entry
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br label %inner.body, !dbg !12
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for.cond.cleanup2: ; preds = %for.cond.cleanup1
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call void @llvm.dbg.value(metadata i32 %add, metadata !9, metadata !DIExpression()), !dbg !12
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tail call void @bar(i32 %add) #0, !dbg !12
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ret void, !dbg !12
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for.cond.cleanup1: ; preds = %for.body
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br i1 false, label %for.cond.preheader, label %for.cond.cleanup2, !dbg !12
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for.body: ; preds = %for.body, %for.cond.preheader
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inner.body: ; preds = %inner.body, %outer.header
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%add = add nsw i32 0, 2, !dbg !12
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call void @llvm.dbg.value(metadata i32 %add, metadata !9, metadata !DIExpression()), !dbg !12
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br i1 false, label %for.body, label %for.cond.cleanup1, !dbg !12
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br i1 false, label %inner.body, label %inner.exit, !dbg !12
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inner.exit: ; preds = %inner.body
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br label %outer.latch
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outer.latch: ; preds = %inner.exit
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br i1 false, label %outer.header, label %outer.exit, !dbg !12
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outer.exit: ; preds = %outer.latch
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call void @llvm.dbg.value(metadata i32 %add, metadata !9, metadata !DIExpression()), !dbg !12
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tail call void @bar(i32 %add), !dbg !12
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br label %exit
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exit: ; preds = %outer.exit
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call void @llvm.dbg.value(metadata i32 %add, metadata !9, metadata !DIExpression()), !dbg !12
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ret void, !dbg !12
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}
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; Function Attrs: nounwind
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declare void @bar(i32) #0
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; For the test case @multi_exit, we cannot update the llvm.dbg.value call in exit,
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; because LCSSA did not insert a PHI node in %exit, as there is no non-debug
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; use.
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; Function Attrs: nounwind readnone speculatable
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declare void @llvm.dbg.value(metadata, metadata, metadata) #1
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; CHECK-LABEL: @multi_exit()
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attributes #0 = { nounwind }
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attributes #1 = { nounwind readnone speculatable }
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; CHECK-LABEL: for.header:
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; CHECK-NEXT: %add = add nsw i32 0, 2
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 %add, metadata [[VAR2:![0-9]+]], metadata !DIExpression())
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; CHECK-LABEL: for.exit1:
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; CHECK-NEXT: [[PN1:%[^ ]*]] = phi i32 [ %add, %for.header ]
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; CHECK-NEXT: br label %for.exit1.succ
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; CHECK-LABEL: for.exit1.succ:
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[PN1]], metadata [[VAR2]], metadata !DIExpression())
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; CHECK-NEXT: call void @bar(i32 [[PN1]])
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; CHECK-LABEL: for.exit2:
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; CHECK-NEXT: [[PN2:%[^ ]*]] = phi i32 [ %add, %for.latch ]
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 [[PN2]], metadata [[VAR2]], metadata !DIExpression())
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; CHECK-NEXT: call void @bar(i32 [[PN2]])
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; CHECK-LABEL: exit:
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; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 %add, metadata [[VAR2]], metadata !DIExpression())
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define void @multi_exit() !dbg !13 {
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entry:
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br label %for.header, !dbg !14
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for.header: ; preds = %for.latch, %entry
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%add = add nsw i32 0, 2, !dbg !14
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call void @llvm.dbg.value(metadata i32 %add, metadata !16, metadata !DIExpression()), !dbg !14
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br i1 false, label %for.latch, label %for.exit1, !dbg !14
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for.latch: ; preds = %for.header
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br i1 false, label %for.header, label %for.exit2, !dbg !14
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for.exit1: ; preds = %for.header
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br label %for.exit1.succ
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for.exit1.succ: ; preds = %for.exit1
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call void @llvm.dbg.value(metadata i32 %add, metadata !16, metadata !DIExpression()), !dbg !14
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tail call void @bar(i32 %add), !dbg !14
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br label %exit
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for.exit2: ; preds = %for.latch
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call void @llvm.dbg.value(metadata i32 %add, metadata !16, metadata !DIExpression()), !dbg !14
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tail call void @bar(i32 %add), !dbg !14
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br label %exit
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exit: ; preds = %for.exit2, %for.exit1.succ
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call void @llvm.dbg.value(metadata i32 %add, metadata !16, metadata !DIExpression()), !dbg !14
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ret void, !dbg !14
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}
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; CHECK: [[VAR]] = !DILocalVariable(name: "sum",
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; CHECK: [[VAR2]] = !DILocalVariable(name: "sum2",
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declare void @bar(i32)
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declare void @llvm.dbg.value(metadata, metadata, metadata)
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!3, !4}
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@ -60,10 +124,14 @@ attributes #1 = { nounwind readnone speculatable }
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!3 = !{i32 2, !"Dwarf Version", i32 4}
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!4 = !{i32 2, !"Debug Info Version", i32 3}
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!5 = !{!"clang version 8.0.0"}
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!6 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 10, type: !7, isLocal: false, isDefinition: true, scopeLine: 10, isOptimized: true, unit: !0, retainedNodes: !8)
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!6 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 10, type: !7, scopeLine: 10, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
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!7 = !DISubroutineType(types: !2)
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!8 = !{!9}
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!9 = !DILocalVariable(name: "sum", scope: !10, file: !1, line: 11, type: !11)
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!10 = !DILexicalBlockFile(scope: !6, file: !1, discriminator: 0)
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!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!12 = !DILocation(line: 0, scope: !10)
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!13 = distinct !DISubprogram(name: "multi_exit", scope: !1, file: !1, line: 10, type: !7, scopeLine: 10, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
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!14 = !DILocation(line: 0, scope: !15)
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!15 = !DILexicalBlockFile(scope: !13, file: !1, discriminator: 0)
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!16 = !DILocalVariable(name: "sum2", scope: !15, file: !1, line: 11, type: !11)
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