Use ConstantExpr::getExtractElement when constant-folding vectors

instead of getAggregateElement. This has the advantage of being
more consistent and allowing higher-level constant folding to
procede even if an inner extract element cannot be folded.

Make ConstantFoldInstruction call ConstantFoldConstantExpression
on the instruction's operands, making it more consistent with 
ConstantFoldConstantExpression itself. This makes sure that
ConstantExprs get TargetData-aware folding before being handed
off as operands for further folding.

This causes more expressions to be folded, but due to a known
shortcoming in constant folding, this currently has the side effect
of stripping a few more nuw and inbounds flags in the non-targetdata
side of constant-fold-gep.ll. This is mostly harmless.

This fixes rdar://11324230.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155682 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 4 deletions

diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 783c32e666..59248c9ca0 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -788,6 +788,10 @@ Constant *llvm::ConstantFoldInstruction(Instruction *I,
       CommonValue = C;
     }
 
+    // Fold the PHI's operands.
+    if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(CommonValue))
+      CommonValue = ConstantFoldConstantExpression(NewCE, TD, TLI);
+
     // If we reach here, all incoming values are the same constant or undef.
     return CommonValue ? CommonValue : UndefValue::get(PN->getType());
   }
@@ -795,12 +799,18 @@ Constant *llvm::ConstantFoldInstruction(Instruction *I,
   // Scan the operand list, checking to see if they are all constants, if so,
   // hand off to ConstantFoldInstOperands.
   SmallVector<Constant*, 8> Ops;
-  for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
-    if (Constant *Op = dyn_cast<Constant>(*i))
-      Ops.push_back(Op);
-    else
+  for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
+    Constant *Op = dyn_cast<Constant>(*i);
+    if (!Op)
       return 0;  // All operands not constant!
 
+    // Fold the Instruction's operands.
+    if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(Op))
+      Op = ConstantFoldConstantExpression(NewCE, TD, TLI);
+
+    Ops.push_back(Op);
+  }
+
   if (const CmpInst *CI = dyn_cast<CmpInst>(I))
     return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
                                            TD, TLI);