[PATCH] D19564: Update Debug Intrinsics in RewriteUsesOfClonedInstructions in LoopRotation

[Thomas Jablin via llvm-commits]

tjablin updated this revision to Diff 55354.
tjablin added a comment.

Update to address David's comments. This version of the patch will never insert additional PHINodes for DbgInfoIntrinsics. Instead, DbgInfoIntrinsics are updated when the needed Value is already live in the DbgInfoIntrinsic's BasicBlock. If the Value is dead, it is replaced with Undef.


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 undef
+
+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
@@ -109,6 +109,38 @@
       // 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. To avoid adding PHINodes, check if the value
+          // is available in UserBB, if not substitute undef.
+          Value *NewVal;
+          if (UserBB == OrigPreheader)
+            NewVal = OrigPreHeaderVal;
+          else if (SSA.HasValueForBlock(UserBB))
+            NewVal = SSA.GetValueInMiddleOfBlock(UserBB);
+          else
+            NewVal = UndefValue::get(OrigHeaderVal->getType());
+          U = MetadataAsValue::get(C, ValueAsMetadata::get(NewVal));
+        }
+      }
+    }
   }
 }
 


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