From d5eb1cbee55b60dd7a5745f47c0b46a3a0b952e3 Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nrotem@apple.com>
Date: Fri, 1 Feb 2013 06:45:40 +0000
Subject: [PATCH] Optimize shift lefts of a constant by a value plus constant
 into a single shift.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174152 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstCombineShifts.cpp         |  6 ++++++
 test/Transforms/InstCombine/shift.ll          | 20 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/lib/Transforms/InstCombine/InstCombineShifts.cpp b/lib/Transforms/InstCombine/InstCombineShifts.cpp
index 8cf76e5e8a9..f9e94f225f2 100644
--- a/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -709,6 +709,12 @@ Instruction *InstCombiner::visitShl(BinaryOperator &I) {
       match(I.getOperand(1), m_Constant(C2)))
     return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A);
 
+  // shl (c1 , add(y , c2)) -> (shl (shl(c1, c2)), y)
+  if (match(I.getOperand(0), m_Constant(C1)) &&
+      match(I.getOperand(1), m_Add(m_Value(A), m_Constant(C2)))) {
+    return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A);
+  }
+
   return 0;
 }
 
diff --git a/test/Transforms/InstCombine/shift.ll b/test/Transforms/InstCombine/shift.ll
index 41f8aa9ee81..117a9060b4a 100644
--- a/test/Transforms/InstCombine/shift.ll
+++ b/test/Transforms/InstCombine/shift.ll
@@ -745,3 +745,23 @@ define i32 @test62(i32 %x) {
 ; CHECK: @test62
 ; CHECK: ashr exact i32 %x, 3
 }
+
+; CHECK: @test63
+; CHECK: shl <4 x i32> <i32 1, i32 2, i32 4, i32 8>, %B
+define <4 x i32> @test63(i32 %n) {
+entry:
+  %K = insertelement <4 x i32> undef, i32 %n, i32 0
+  %B = shufflevector <4 x i32> %K, <4 x i32> undef, <4 x i32> zeroinitializer
+  %A = add <4 x i32> %B, <i32 0, i32 1, i32 2, i32 3>
+  %T = shl <4 x i32> <i32 1, i32 1, i32 1, i32 1>, %A
+  ret <4 x i32> %T
+}
+
+; CHECK: @test64
+; CHECK: shl i32 524288, %n
+define i32 @test64(i32 %n) {
+entry:
+  %A = add i32 %n, 19
+  %T = shl i32 1 , %A
+  ret i32 %T
+}
-- 
2.34.1