[llvm-commits] [llvm] r97794 - in /llvm/trunk: lib/Transforms/Scalar/Reassociate.cpp test/Transforms/Reassociate/crash.ll

[Chris Lattner]

Author: lattner
Date: Fri Mar  5 01:18:54 2010
New Revision: 97794

URL: http://llvm.org/viewvc/llvm-project?rev=97794&view=rev
Log:
fix a nice subtle reassociate bug which would only occur
in a very specific use pattern embodied in the carefully
reduced testcase.

Modified:
    llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp
    llvm/trunk/test/Transforms/Reassociate/crash.ll

Modified: llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp?rev=97794&r1=97793&r2=97794&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp Fri Mar  5 01:18:54 2010
@@ -597,19 +597,35 @@
 
 /// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
 /// add its operands as factors, otherwise add V to the list of factors.
+///
+/// Ops is the top-level list of add operands we're trying to factor.
 static void FindSingleUseMultiplyFactors(Value *V,
-                                         SmallVectorImpl<Value*> &Factors) {
+                                         SmallVectorImpl<Value*> &Factors,
+                                       const SmallVectorImpl<ValueEntry> &Ops,
+                                         bool IsRoot) {
   BinaryOperator *BO;
-  if ((!V->hasOneUse() && !V->use_empty()) ||
+  if (!(V->hasOneUse() || V->use_empty()) || // More than one use.
       !(BO = dyn_cast<BinaryOperator>(V)) ||
       BO->getOpcode() != Instruction::Mul) {
     Factors.push_back(V);
     return;
   }
   
+  // If this value has a single use because it is another input to the add
+  // tree we're reassociating and we dropped its use, it actually has two
+  // uses and we can't factor it.
+  if (!IsRoot) {
+    for (unsigned i = 0, e = Ops.size(); i != e; ++i)
+      if (Ops[i].Op == V) {
+        Factors.push_back(V);
+        return;
+      }
+  }
+  
+  
   // Otherwise, add the LHS and RHS to the list of factors.
-  FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
-  FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
+  FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops, false);
+  FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops, false);
 }
 
 /// OptimizeAndOrXor - Optimize a series of operands to an 'and', 'or', or 'xor'
@@ -753,7 +769,7 @@
     
     // Compute all of the factors of this added value.
     SmallVector<Value*, 8> Factors;
-    FindSingleUseMultiplyFactors(BOp, Factors);
+    FindSingleUseMultiplyFactors(BOp, Factors, Ops, true);
     assert(Factors.size() > 1 && "Bad linearize!");
     
     // Add one to FactorOccurrences for each unique factor in this op.

Modified: llvm/trunk/test/Transforms/Reassociate/crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Reassociate/crash.ll?rev=97794&r1=97793&r2=97794&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/Reassociate/crash.ll (original)
+++ llvm/trunk/test/Transforms/Reassociate/crash.ll Fri Mar  5 01:18:54 2010
@@ -23,11 +23,22 @@
   %3 = add nsw i32 undef, %1
   %4 = add nsw i32 %3, %2
   %5 = add nsw i32 %4, 4
-  %6 = shl i32 %0, 3                              ; <i32> [#uses=1]
+  %6 = shl i32 %0, 3
   %7 = add nsw i32 %5, %6
   br label %bb4.i9
 
-bb4.i9:                                           ; preds = %bb3.i7, %bb1.i25.i
+bb4.i9:
   %8 = add nsw i32 undef, %1
   ret i32 0
 }
+
+
+define i32 @test3(i32 %Arg, i32 %x1, i32 %x2, i32 %x3) {
+ %A = mul i32 %x1, %Arg
+ %B = mul i32 %Arg, %x2 ;; Part of add operation being factored, also used by C
+ %C = mul i32 %x3, %B
+
+ %D = add i32 %A, %B
+ %E = add i32 %D, %C
+  ret i32 %E
+}