Use a sign-extend instead of a zero-extend when promoting a

trip count value when the original loop iteration condition is
signed and the canonical induction variable won't undergo signed
overflow. This isn't required for correctness; it just preserves
more information about original loop iteration values.

Add a getTruncateOrSignExtend method to ScalarEvolution,
following getTruncateOrZeroExtend.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64918 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index 963117fdd5..b001077ca7 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -264,6 +264,11 @@ namespace llvm {
     /// extended, it is zero extended.
     SCEVHandle getTruncateOrZeroExtend(const SCEVHandle &V, const Type *Ty);
 
+    /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion
+    /// of the input value to the specified type.  If the type must be
+    /// extended, it is sign extended.
+    SCEVHandle getTruncateOrSignExtend(const SCEVHandle &V, const Type *Ty);
+
     /// getIntegerSCEV - Given an integer or FP type, create a constant for the
     /// specified signed integer value and return a SCEV for the constant.
     SCEVHandle getIntegerSCEV(int Val, const Type *Ty);