[llvm-commits] [llvm] r108455 - /llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

[Dan Gohman]

Author: djg
Date: Thu Jul 15 15:24:58 2010
New Revision: 108455

URL: http://llvm.org/viewvc/llvm-project?rev=108455&view=rev
Log:
Don't merge uses when they are targetting fixup sites with
different widths. In a use with a narrower fixup, formulae
may be wider than the fixup, in which case the high bits
aren't necessarily meaningful, so it isn't safe to reuse
them for uses with wider fixups.

This fixes PR7618, though the testcase is too large for a
reasonable regression test, since it heavily dependes on
hitting LSR's heuristics in a certain way.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=108455&r1=108454&r2=108455&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Thu Jul 15 15:24:58 2010
@@ -965,6 +965,12 @@
   /// may be used.
   bool AllFixupsOutsideLoop;
 
+  /// WidestFixupType - This records the widest use type for any fixup using
+  /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
+  /// max fixup widths to be equivalent, because the narrower one may be relying
+  /// on the implicit truncation to truncate away bogus bits.
+  const Type *WidestFixupType;
+
   /// Formulae - A list of ways to build a value that can satisfy this user.
   /// After the list is populated, one of these is selected heuristically and
   /// used to formulate a replacement for OperandValToReplace in UserInst.
@@ -976,7 +982,8 @@
   LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T),
                                       MinOffset(INT64_MAX),
                                       MaxOffset(INT64_MIN),
-                                      AllFixupsOutsideLoop(true) {}
+                                      AllFixupsOutsideLoop(true),
+                                      WidestFixupType(0) {}
 
   bool HasFormulaWithSameRegs(const Formula &F) const;
   bool InsertFormula(const Formula &F);
@@ -1083,6 +1090,9 @@
 
   if (AllFixupsOutsideLoop)
     OS << ", all-fixups-outside-loop";
+
+  if (WidestFixupType)
+    OS << ", widest fixup type: " << *WidestFixupType;
 }
 
 void LSRUse::dump() const {
@@ -1928,6 +1938,7 @@
     if (&LU != &OrigLU &&
         LU.Kind != LSRUse::ICmpZero &&
         LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
+        LU.WidestFixupType == OrigLU.WidestFixupType &&
         LU.HasFormulaWithSameRegs(OrigF)) {
       for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
            E = LU.Formulae.end(); I != E; ++I) {
@@ -2066,6 +2077,10 @@
     LF.Offset = P.second;
     LSRUse &LU = Uses[LF.LUIdx];
     LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
+    if (!LU.WidestFixupType ||
+        SE.getTypeSizeInBits(LU.WidestFixupType) <
+        SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
+      LU.WidestFixupType = LF.OperandValToReplace->getType();
 
     // If this is the first use of this LSRUse, give it a formula.
     if (LU.Formulae.empty()) {
@@ -2195,6 +2210,10 @@
         LF.Offset = P.second;
         LSRUse &LU = Uses[LF.LUIdx];
         LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
+        if (!LU.WidestFixupType ||
+            SE.getTypeSizeInBits(LU.WidestFixupType) <
+            SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
+          LU.WidestFixupType = LF.OperandValToReplace->getType();
         InsertSupplementalFormula(U, LU, LF.LUIdx);
         CountRegisters(LU.Formulae.back(), Uses.size() - 1);
         break;