[llvm-commits] [llvm] r159426 - in /llvm/trunk: lib/Transforms/Scalar/Reassociate.cpp test/Transforms/Reassociate/crash.ll

[Duncan Sands]

Author: baldrick
Date: Fri Jun 29 08:25:06 2012
New Revision: 159426

URL: http://llvm.org/viewvc/llvm-project?rev=159426&view=rev
Log:
Fix a reassociate crash on sozefx when compiling with dragonegg+gcc-4.7 due to
the optimizers producing a multiply expression with more multiplications than
the original (!).

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=159426&r1=159425&r2=159426&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/Reassociate.cpp Fri Jun 29 08:25:06 2012
@@ -674,8 +674,6 @@
   // Flags are cleared from the operator in ExpressionChanged up to I inclusive.
   BinaryOperator *ExpressionChanged = 0;
   for (unsigned i = 0; ; ++i) {
-    assert(!NodesToRewrite.empty() &&
-           "Optimized expressions has more nodes than original!");
     BinaryOperator *Op = NodesToRewrite.pop_back_val();
 
     // The last operation (which comes earliest in the IR) is special as both
@@ -753,9 +751,19 @@
     }
 
     // Otherwise, grab a spare node from the original expression and use that as
-    // the left-hand side.
-    assert(!NodesToRewrite.empty() &&
-           "Optimized expressions has more nodes than original!");
+    // the left-hand side.  If there are no nodes left then the optimizers made
+    // an expression with more nodes than the original!  This usually means that
+    // they did something stupid but it might mean that the problem was just too
+    // hard (finding the mimimal number of multiplications needed to realize a
+    // multiplication expression is NP-complete).  Whatever the reason, smart or
+    // stupid, create a new node if there are none left.
+    if (NodesToRewrite.empty()) {
+      Constant *Undef = UndefValue::get(I->getType());
+      BinaryOperator *N = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
+                                                 Undef, Undef, "", I);
+      NodesToRewrite.push_back(N);
+    }
+
     DEBUG(dbgs() << "RA: " << *Op << '\n');
     Op->setOperand(0, NodesToRewrite.back());
     DEBUG(dbgs() << "TO: " << *Op << '\n');

Modified: llvm/trunk/test/Transforms/Reassociate/crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Reassociate/crash.ll?rev=159426&r1=159425&r2=159426&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/Reassociate/crash.ll (original)
+++ llvm/trunk/test/Transforms/Reassociate/crash.ll Fri Jun 29 08:25:06 2012
@@ -133,3 +133,14 @@
   %t7 = mul i8 %t6, %t0
   ret i8 %t7
 }
+
+define i32 @sozefx_(i32 %x, i32 %y) {
+  %t0 = sub i32 %x, %x
+  %t1 = mul i32 %t0, %t0
+  %t2 = mul i32 %x, %t0
+  %t3 = mul i32 %t1, %t1
+  %t4 = add i32 %t2, %t3
+  %t5 = mul i32 %x, %y
+  %t6 = add i32 %t4, %t5
+  ret i32 %t6
+}