LICM shouldn't sink/delete debug information. Fix this and add a testcase.

For now the metadata of sinked/hoisted instructions is still wrong, but that'll
be fixed when instructions will have debug metadata directly attached.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83786 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 94 insertions, 1 deletions

diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index 6df246f..40af0a8 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -35,6 +35,7 @@
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Constants.h"
 #include "llvm/DerivedTypes.h"
+#include "llvm/IntrinsicInst.h"
 #include "llvm/Instructions.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Analysis/LoopInfo.h"
@@ -140,6 +141,10 @@ namespace {
     ///
     void HoistRegion(DomTreeNode *N);
 
+    // Cleanup debug information (remove stoppoints with no coressponding
+    // instructions).
+    void CleanupDbgInfoRegion(DomTreeNode *N);
+
     /// inSubLoop - Little predicate that returns true if the specified basic
     /// block is in a subloop of the current one, not the current one itself.
     ///
@@ -287,6 +292,7 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) {
   //
   SinkRegion(DT->getNode(L->getHeader()));
   HoistRegion(DT->getNode(L->getHeader()));
+  CleanupDbgInfoRegion(DT->getNode(L->getHeader()));
 
   // Now that all loop invariants have been removed from the loop, promote any
   // memory references to scalars that we can...
@@ -338,6 +344,35 @@ void LICM::SinkRegion(DomTreeNode *N) {
   }
 }
 
+void LICM::CleanupDbgInfoRegion(DomTreeNode *N) {
+  BasicBlock *BB = N->getBlock();
+
+  // If this subregion is not in the top level loop at all, exit.
+  if (!CurLoop->contains(BB)) return;
+
+  // We are processing blocks in reverse dfo, so process children first...
+  const std::vector<DomTreeNode*> &Children = N->getChildren();
+  for (unsigned i = 0, e = Children.size(); i != e; ++i)
+    CleanupDbgInfoRegion(Children[i]);
+
+  // Only need to process the contents of this block if it is not part of a
+  // subloop (which would already have been processed).
+  if (inSubLoop(BB)) return;
+
+  // We modify the basicblock, so don't cache end()
+  for (BasicBlock::iterator I=BB->begin(); I != BB->end();) {
+    Instruction *Last = 0;
+    // Remove consecutive dbgstoppoints, leave only last
+    do {
+      if (Last) {
+        Last->eraseFromParent();
+        Changed = true;
+      }
+      Last = I;
+      ++I;
+    } while (isa<DbgStopPointInst>(Last) && isa<DbgStopPointInst>(I));
+  }
+}
 
 /// HoistRegion - Walk the specified region of the CFG (defined by all blocks
 /// dominated by the specified block, and that are in the current loop) in depth
@@ -392,6 +427,10 @@ bool LICM::canSinkOrHoistInst(Instruction &I) {
       Size = AA->getTypeStoreSize(LI->getType());
     return !pointerInvalidatedByLoop(LI->getOperand(0), Size);
   } else if (CallInst *CI = dyn_cast<CallInst>(&I)) {
+    if (isa<DbgStopPointInst>(CI)) {
+      // Don't hoist/sink dbgstoppoints, we handle them separately
+      return false;
+    }
     // Handle obvious cases efficiently.
     AliasAnalysis::ModRefBehavior Behavior = AA->getModRefBehavior(CI);
     if (Behavior == AliasAnalysis::DoesNotAccessMemory)
@@ -489,7 +528,6 @@ void LICM::sink(Instruction &I) {
       // Move the instruction to the start of the exit block, after any PHI
       // nodes in it.
       I.removeFromParent();
-
       BasicBlock::iterator InsertPt = ExitBlocks[0]->getFirstNonPHI();
       ExitBlocks[0]->getInstList().insert(InsertPt, &I);
     }
diff --git a/test/Transforms/LICM/licm_preserve_dbginfo.ll b/test/Transforms/LICM/licm_preserve_dbginfo.ll
new file mode 100644
index 0000000..e013c27
--- /dev/null
+++ b/test/Transforms/LICM/licm_preserve_dbginfo.ll
@@ -0,0 +1,55 @@
+; RUN: opt -licm -S <%s | FileCheck %s
+; Test that licm doesn't sink/delete debug info.
+define i32 @foo(i32 %a, i32 %j) nounwind {
+entry:
+;CHECK: entry:
+  call void @llvm.dbg.func.start(metadata !0)
+  call void @llvm.dbg.stoppoint(i32 3, i32 5, metadata !1)
+;CHECK: %mul = mul i32 %j, %j
+  br label %for.cond
+
+for.cond:
+;CHECK: for.cond:
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+  %s.0 = phi i32 [ 0, %entry ], [ %add, %for.inc ]
+  call void @llvm.dbg.stoppoint(i32 4, i32 5, metadata !1)
+; CHECK: call void @llvm.dbg.stoppoint(i32 4, i32 5, metadata !1)
+  %cmp = icmp slt i32 %i.0, %a
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:
+;CHECK: for.body:
+  call void @llvm.dbg.stoppoint(i32 5, i32 2, metadata !1)
+;CHECK: call void @llvm.dbg.stoppoint(i32 5, i32 2, metadata !1)
+  %mul = mul i32 %j, %j
+  %add = add nsw i32 %s.0, %mul
+  br label %for.inc
+
+for.inc:
+;CHECK: for.inc:
+  call void @llvm.dbg.stoppoint(i32 4, i32 18, metadata !1)
+;CHECK: call void @llvm.dbg.stoppoint(i32 4, i32 18, metadata !1)
+  %inc = add nsw i32 %i.0, 1
+  br label %for.cond
+
+for.end:
+  call void @llvm.dbg.stoppoint(i32 7, i32 5, metadata !1)
+  br label %0
+
+; <label>:0                                       ; preds = %for.end
+  call void @llvm.dbg.stoppoint(i32 8, i32 1, metadata !1)
+  call void @llvm.dbg.region.end(metadata !0)
+  ret i32 %s.0
+}
+
+declare void @llvm.dbg.func.start(metadata) nounwind readnone
+
+declare void @llvm.dbg.declare({ }*, metadata) nounwind readnone
+
+declare void @llvm.dbg.stoppoint(i32, i32, metadata) nounwind readnone
+
+declare void @llvm.dbg.region.end(metadata) nounwind readnone
+
+!0 = metadata !{i32 458798, i32 0, metadata !1, metadata !"foo", metadata !"foo", metadata !"foo", metadata !1, i32 2, metadata !2, i1 false, i1 true}; [DW_TAG_subprogram ]
+!1 = metadata !{i32 458769, i32 0, i32 12, metadata !"licm.c", metadata !"/home/edwin", metadata !"clang 1.1", i1 true, i1 false, metadata !"", i32 0}; [DW_TAG_compile_unit ]
+!2 = metadata !{i32 458788, metadata !1, metadata !"int", metadata !1, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5}; [DW_TAG_base_type ]