From 40157d5c4db4a75ebc845022961a89661c728fea Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Thu, 27 Nov 2014 07:25:21 +0000
Subject: [PATCH] InstCombine: Restore optimizations lost in r210006

This restores our ability to optimize:
(X & C) == 0 ? X ^ C : X  into  X | C
(X & C) != 0 ? X ^ C : X  into  X & ~C

llvm-svn: 222871
---
 .../Transforms/InstCombine/InstCombineSelect.cpp   | 28 ++++++++++++
 llvm/test/Transforms/InstCombine/select.ll         | 53 ++++++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 8e2a7d5..83a2f2c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -617,6 +617,34 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
     }
   }
 
+  {
+    Value *X;
+    const APInt *Y, *C;
+    if (match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
+        match(CmpRHS, m_Zero())) {
+      Value *V = nullptr;
+      // (X & Y) == 0 ? X : X ^ Y  --> X & ~Y
+      if (Pred == ICmpInst::ICMP_EQ && TrueVal == X &&
+          match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+        V = Builder->CreateAnd(X, ~(*Y));
+      // (X & Y) != 0 ? X ^ Y : X  --> X & ~Y
+      else if (Pred == ICmpInst::ICMP_NE && FalseVal == X &&
+               match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+        V = Builder->CreateAnd(X, ~(*Y));
+      // (X & Y) == 0 ? X ^ Y : X  --> X | Y
+      else if (Pred == ICmpInst::ICMP_EQ && FalseVal == X &&
+               match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+        V = Builder->CreateOr(X, *Y);
+      // (X & Y) != 0 ? X : X ^ Y  --> X | Y
+      else if (Pred == ICmpInst::ICMP_NE && TrueVal == X &&
+               match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+        V = Builder->CreateOr(X, *Y);
+
+      if (V)
+        return ReplaceInstUsesWith(SI, V);
+    }
+  }
+
   if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder))
     return ReplaceInstUsesWith(SI, V);
 
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index bdf48e4..db3d77a 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -997,6 +997,59 @@ define <2 x i32> @select_icmp_eq_and_1_0_or_vector_of_2s(i32 %x, <2 x i32> %y) {
   ret <2 x i32> %select
 }
 
+; CHECK-LABEL: @select_icmp_and_8_ne_0_xor_8(
+; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %x, -9
+; CHECK-NEXT: ret i32 [[AND]]
+define i32 @select_icmp_and_8_ne_0_xor_8(i32 %x) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %xor = xor i32 %x, 8
+  %x.xor = select i1 %cmp, i32 %x, i32 %xor
+  ret i32 %x.xor
+}
+
+; CHECK-LABEL: @select_icmp_and_8_eq_0_xor_8(
+; CHECK-NEXT: [[OR:%[a-z0-9]+]] = or i32 %x, 8
+; CHECK-NEXT: ret i32 [[OR]]
+define i32 @select_icmp_and_8_eq_0_xor_8(i32 %x) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %xor = xor i32 %x, 8
+  %xor.x = select i1 %cmp, i32 %xor, i32 %x
+  ret i32 %xor.x
+}
+
+; CHECK-LABEL: @select_icmp_x_and_8_eq_0_y_xor_8(
+; CHECK: select i1 %cmp, i64 %y, i64 %xor
+define i64 @select_icmp_x_and_8_eq_0_y_xor_8(i32 %x, i64 %y) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %xor = xor i64 %y, 8
+  %y.xor = select i1 %cmp, i64 %y, i64 %xor
+  ret i64 %y.xor
+}
+
+; CHECK-LABEL: @select_icmp_x_and_8_ne_0_y_xor_8(
+; CHECK: select i1 %cmp, i64 %xor, i64 %y
+define i64 @select_icmp_x_and_8_ne_0_y_xor_8(i32 %x, i64 %y) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %xor = xor i64 %y, 8
+  %xor.y = select i1 %cmp, i64 %xor, i64 %y
+  ret i64 %xor.y
+}
+
+; CHECK-LABEL: @select_icmp_x_and_8_ne_0_y_or_8(
+; CHECK: xor i64 %1, 8
+; CHECK: or i64 %2, %y
+define i64 @select_icmp_x_and_8_ne_0_y_or_8(i32 %x, i64 %y) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %or = or i64 %y, 8
+  %or.y = select i1 %cmp, i64 %or, i64 %y
+  ret i64 %or.y
+}
+
 define i32 @test65(i64 %x) {
   %1 = and i64 %x, 16
   %2 = icmp ne i64 %1, 0
-- 
2.7.4