[PATCH] D19564: Update Debug Intrinsics in RewriteUsesOfClonedInstructions in LoopRotation
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Wed Apr 27 11:27:26 PDT 2016
Does this cause changes in non-debug IR in the presence of debug info
intrinsics? (you mention that "If there were uses of values produced by
these instructions that were outside the loop, we have to insert PHI nodes
to merge the two values." - that sounds like it could be a problem, as
enabling debug info is not intended to change optimization/code generation)
On Tue, Apr 26, 2016 at 3:34 PM, Thomas Jablin via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> tjablin created this revision.
> tjablin added reviewers: kbarton, hfinkel, cycheng.
> tjablin added a subscriber: llvm-commits.
> Herald added a subscriber: mzolotukhin.
>
> Loop rotation clones instruction from the old header into the preheader.
> If there were uses of values produced by these instructions that were
> outside the loop, we have to insert PHI nodes to merge the two values. If
> the values are used by DbgIntrinsics they will be used as a MetadataAsValue
> of a ValueAsMetadata of the original values, and iterating all of the uses
> of the original value will not update the DbgIntrinsics. The new code
> checks if the values are used by DbgIntrinsics and if so, updates them
> using essentially the same logic as the original code.
>
> The attached testcase demonstrates the issue. Without the fix, the
> DbgIntrinic outside the loop uses values computed inside the loop, even
> though these values do not dominate the DbgIntrinsic.
>
> http://reviews.llvm.org/D19564
>
> Files:
> lib/Transforms/Scalar/LoopRotation.cpp
> test/Transforms/LoopRotate/dbgvalue.ll
>
> Index: test/Transforms/LoopRotate/dbgvalue.ll
> ===================================================================
> --- test/Transforms/LoopRotate/dbgvalue.ll
> +++ test/Transforms/LoopRotate/dbgvalue.ll
> @@ -7,6 +7,7 @@
> ; CHECK-LABEL: define i32 @tak(
> ; CHECK: entry
> ; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 %x
> +; CHECK: tail call void @llvm.dbg.value(metadata i32 %call
>
> entry:
> br label %tailrecurse
> @@ -37,6 +38,44 @@
> ret i32 %z.tr, !dbg !17
> }
>
> +define i32 @tak2(i32 %x, i32 %y, i32 %z) nounwind ssp !dbg !0 {
> +; CHECK-LABEL: define i32 @tak2(
> +; CHECK: entry
> +; CHECK: tail call void @llvm.dbg.value(metadata i32 %x.tr
> +; CHECK: tail call void @llvm.dbg.value(metadata i32 %x.tr
> +
> +entry:
> + br label %tailrecurse
> +
> +tailrecurse: ; preds = %if.then,
> %entry
> + %x.tr = phi i32 [ %x, %entry ], [ %call, %if.then ]
> + %y.tr = phi i32 [ %y, %entry ], [ %call9, %if.then ]
> + %z.tr = phi i32 [ %z, %entry ], [ %call14, %if.then ]
> + %cmp = icmp slt i32 %y.tr, %x.tr, !dbg !12
> + br i1 %cmp, label %if.then, label %if.end, !dbg !12
> +
> +if.then: ; preds = %tailrecurse
> + tail call void @llvm.dbg.value(metadata i32 %x.tr, i64 0, metadata !6,
> metadata !DIExpression()), !dbg !7
> + tail call void @llvm.dbg.value(metadata i32 %y.tr, i64 0, metadata !8,
> metadata !DIExpression()), !dbg !9
> + tail call void @llvm.dbg.value(metadata i32 %z.tr, i64 0, metadata
> !10, metadata !DIExpression()), !dbg !11
> + %sub = sub nsw i32 %x.tr, 1, !dbg !14
> + %call = tail call i32 @tak(i32 %sub, i32 %y.tr, i32 %z.tr), !dbg !14
> + %sub6 = sub nsw i32 %y.tr, 1, !dbg !14
> + %call9 = tail call i32 @tak(i32 %sub6, i32 %z.tr, i32 %x.tr), !dbg !14
> + %sub11 = sub nsw i32 %z.tr, 1, !dbg !14
> + %call14 = tail call i32 @tak(i32 %sub11, i32 %x.tr, i32 %y.tr), !dbg
> !14
> + br label %tailrecurse
> +
> +if.end: ; preds = %tailrecurse
> + tail call void @llvm.dbg.value(metadata i32 %x.tr, i64 0, metadata !6,
> metadata !DIExpression()), !dbg !7
> + tail call void @llvm.dbg.value(metadata i32 %y.tr, i64 0, metadata !8,
> metadata !DIExpression()), !dbg !9
> + tail call void @llvm.dbg.value(metadata i32 %z.tr, i64 0, metadata
> !10, metadata !DIExpression()), !dbg !11
> + br label %return, !dbg !16
> +
> +return: ; preds = %if.end
> + ret i32 %z.tr, !dbg !17
> +}
> +
> @channelColumns = external global i64
> @horzPlane = external global i8*, align 8
>
> Index: lib/Transforms/Scalar/LoopRotation.cpp
> ===================================================================
> --- lib/Transforms/Scalar/LoopRotation.cpp
> +++ lib/Transforms/Scalar/LoopRotation.cpp
> @@ -108,6 +108,33 @@
>
> // Anything else can be handled by SSAUpdater.
> SSA.RewriteUse(U);
> +
> + // Replace MetadataAsValue(ValueAsMetadata(OrigHeaderVal)) uses in
> debug
> + // intrinsics
> + LLVMContext &C = OrigHeader->getContext();
> + if (ValueAsMetadata *VAM =
> ValueAsMetadata::getIfExists(OrigHeaderVal)) {
> + if (MetadataAsValue *MAV = MetadataAsValue::getIfExists(C, VAM)) {
> + for (auto UI = MAV->use_begin(), E = MAV->use_end(); UI != E; )
> {
> + // Grab the use before incrementing the iterator.
> + Use &U = *UI++;
> + DbgInfoIntrinsic *UserInst =
> cast<DbgInfoIntrinsic>(U.getUser());
> + BasicBlock *UserBB = UserInst->getParent();
> +
> + // The original users in the OrigHeader are already using the
> + // original definitions.
> + if (UserBB == OrigHeader)
> + continue;
> +
> + // Users in the OrigPreHeader need to use the value to which
> the
> + // original definitions are mapped and anything else can be
> handled
> + // by the SSAUpdater
> + Value *NewVal = UserBB == OrigPreheader ?
> + OrigPreHeaderVal :
> + SSA.GetValueInMiddleOfBlock(UserBB);
> + U = MetadataAsValue::get(C, ValueAsMetadata::get(NewVal));
> + }
> + }
> + }
> }
> }
> }
>
>
>
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