Propagate zest through logical shift.

llvm-svn: 91378

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -3278,6 +3278,16 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
     if (SCC.getNode()) return SCC;
   }
 
+  // (zext (shl (zext x), y)) -> (shl (zext x), (zext y))
+  if ((N0.getOpcode() == ISD::SHL || N0.getOpcode() == ISD::SRL) &&
+      N0.getOperand(0).getOpcode() == ISD::ZERO_EXTEND &&
+      N0.hasOneUse()) {
+    DebugLoc dl = N->getDebugLoc();
+    return DAG.getNode(N0.getOpcode(), dl, VT,
+                       DAG.getNode(ISD::ZERO_EXTEND, dl, VT, N0.getOperand(0)),
+                       DAG.getNode(ISD::ZERO_EXTEND, dl, VT, N0.getOperand(1)));
+  }
+
   return SDValue();
 }
 

llvm/test/CodeGen/X86/setcc.ll

@@ -0,0 +1,13 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+
+define zeroext i16 @t1(i16 zeroext %x) nounwind readnone ssp {
+entry:
+; CHECK: t1:
+; CHECK: seta %al
+; CHECK: movzbl %al, %eax
+; CHECK: shll $5, %eax
+  %0 = icmp ugt i16 %x, 26                        ; <i1> [#uses=1]
+  %iftmp.1.0 = select i1 %0, i16 32, i16 0        ; <i16> [#uses=1]
+  ret i16 %iftmp.1.0
+}
+

llvm/test/CodeGen/X86/zext-shl.ll

@@ -0,0 +1,38 @@
+; RUN: llc < %s -march=x86 | FileCheck %s
+
+define i32 @t1(i8 zeroext %x) nounwind readnone ssp {
+entry:
+; CHECK: t1:
+; CHECK: shll
+; CHECK-NOT: movzwl
+; CHECK: ret
+  %0 = zext i8 %x to i16
+  %1 = shl i16 %0, 5
+  %2 = zext i16 %1 to i32
+  ret i32 %2
+}
+
+define i32 @t2(i8 zeroext %x) nounwind readnone ssp {
+entry:
+; CHECK: t2:
+; CHECK: shrl
+; CHECK-NOT: movzwl
+; CHECK: ret
+  %0 = zext i8 %x to i16
+  %1 = lshr i16 %0, 3
+  %2 = zext i16 %1 to i32
+  ret i32 %2
+}
+
+define i32 @t3(i8 zeroext %x, i8 zeroext %y) nounwind readnone ssp {
+entry:
+; CHECK: t3:
+; CHECK: shll
+; CHECK-NOT: movzwl
+; CHECK: ret
+  %0 = zext i8 %x to i16
+  %1 = zext i8 %y to i16
+  %2 = shl i16 %0, %1
+  %3 = zext i16 %2 to i32
+  ret i32 %3
+}