From: Wojciech Matyjewicz <wmatyjewicz@fastmail.fm>
Date: Sun, 15 Jun 2008 19:07:39 +0000 (+0000)
Subject: Fix PR2434. When scanning for exising binary operator to reuse don't
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8a08769bad43a22fae2845bb0ba0fd1266cd55c8;p=oota-llvm.git

Fix PR2434. When scanning for exising binary operator to reuse don't
take into account the instrucion pointed by InsertPt. Thanks to it,
returning the new value of InsertPt to the InsertBinop() caller can be
avoided. The bug was, actually, in visitAddRecExpr() method which wasn't
correctly handling changes of InsertPt. There shouldn't be any
performance regression, as -gvn pass (run after -indvars) removes any
redundant binops.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52291 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/Analysis/ScalarEvolutionExpander.h b/include/llvm/Analysis/ScalarEvolutionExpander.h
index daff373348b..9a69b241651 100644
--- a/include/llvm/Analysis/ScalarEvolutionExpander.h
+++ b/include/llvm/Analysis/ScalarEvolutionExpander.h
@@ -88,7 +88,7 @@ namespace llvm {
     /// InsertBinop - Insert the specified binary operator, doing a small amount
     /// of work to avoid inserting an obviously redundant operation.
     static Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
-                              Value *RHS, Instruction *&InsertPt);
+                              Value *RHS, Instruction *InsertPt);
   protected:
     Value *expand(SCEV *S);
     
diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index a241960b374..9872ced519e 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -73,7 +73,7 @@ Value *SCEVExpander::InsertCastOfTo(Instruction::CastOps opcode, Value *V,
 /// InsertBinop - Insert the specified binary operator, doing a small amount
 /// of work to avoid inserting an obviously redundant operation.
 Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
-                                 Value *RHS, Instruction *&InsertPt) {
+                                 Value *RHS, Instruction *InsertPt) {
   // Fold a binop with constant operands.
   if (Constant *CLHS = dyn_cast<Constant>(LHS))
     if (Constant *CRHS = dyn_cast<Constant>(RHS))
@@ -81,21 +81,21 @@ Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
 
   // Do a quick scan to see if we have this binop nearby.  If so, reuse it.
   unsigned ScanLimit = 6;
-  for (BasicBlock::iterator IP = InsertPt, E = InsertPt->getParent()->begin();
-       ScanLimit; --IP, --ScanLimit) {
-    if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(IP))
-      if (BinOp->getOpcode() == Opcode && BinOp->getOperand(0) == LHS &&
-          BinOp->getOperand(1) == RHS) {
-        // If we found the instruction *at* the insert point, insert later
-        // instructions after it.
-        if (BinOp == InsertPt)
-          InsertPt = ++IP;
-        return BinOp;
-      }
-    if (IP == E) break;
+  BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
+  if (InsertPt != BlockBegin) {
+    // Scanning starts from the last instruction before InsertPt.
+    BasicBlock::iterator IP = InsertPt;
+    --IP;
+    for (; ScanLimit; --IP, --ScanLimit) {
+      if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(IP))
+        if (BinOp->getOpcode() == Opcode && BinOp->getOperand(0) == LHS &&
+            BinOp->getOperand(1) == RHS)
+          return BinOp;
+      if (IP == BlockBegin) break;
+    }
   }
-
-  // If we don't have 
+  
+  // If we haven't found this binop, insert it.
   return BinaryOperator::Create(Opcode, LHS, RHS, "tmp", InsertPt);
 }
 
diff --git a/test/Transforms/IndVarsSimplify/2008-06-15-SCEVExpanderBug.ll b/test/Transforms/IndVarsSimplify/2008-06-15-SCEVExpanderBug.ll
new file mode 100644
index 00000000000..aac8d978946
--- /dev/null
+++ b/test/Transforms/IndVarsSimplify/2008-06-15-SCEVExpanderBug.ll
@@ -0,0 +1,17 @@
+; RUN: llvm-as < %s | opt -indvars -disable-output
+; PR2434
+
+define fastcc void @regcppop() nounwind  {
+entry:
+	%tmp61 = add i32 0, -5		; <i32> [#uses=1]
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%PL_savestack_ix.tmp.0 = phi i32 [ %tmp61, %entry ], [ %tmp127, %bb ]		; <i32> [#uses=2]
+	%indvar10 = phi i32 [ 0, %entry ], [ %indvar.next11, %bb ]		; <i32> [#uses=2]
+	%tmp13 = mul i32 %indvar10, -4		; <i32> [#uses=0]
+	%tmp111 = add i32 %PL_savestack_ix.tmp.0, -3		; <i32> [#uses=0]
+	%tmp127 = add i32 %PL_savestack_ix.tmp.0, -4		; <i32> [#uses=1]
+	%indvar.next11 = add i32 %indvar10, 1		; <i32> [#uses=1]
+	br label %bb
+}