Add a missing SCEV simplification sext(zext x) --> zext x.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123832 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index b3df92611950e895a03e5d0d876098b4992fc335..ce0418849094b9d86175771682f6a1909fb6371d 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -994,6 +994,10 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
   if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
     return getSignExtendExpr(SS->getOperand(), Ty);
 
+  // sext(zext(x)) --> zext(x)
+  if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
+    return getZeroExtendExpr(SZ->getOperand(), Ty);
+
   // Before doing any expensive analysis, check to see if we've already
   // computed a SCEV for this Op and Ty.
   FoldingSetNodeID ID;

diff --git a/test/Analysis/ScalarEvolution/fold.ll b/test/Analysis/ScalarEvolution/fold.ll
new file mode 100644 (file)
index 0000000..202ddd4
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/fold.ll
@@ -0,0 +1,8 @@
+; RUN: opt -analyze -scalar-evolution %s -S | FileCheck %s
+
+define i16 @test(i8 %x) {
+  %A = zext i8 %x to i12
+  %B = sext i12 %A to i16
+; CHECK: zext i8 %x to i16
+  ret i16 %B
+}