From c6a5e1dd4f595b2ff437ee47345b9c27864ad232 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Thu, 27 Nov 2014 06:32:46 +0000
Subject: [PATCH] InstSimplify: Restore optimizations lost in r210006

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

llvm-svn: 222868
---
 llvm/lib/Analysis/InstructionSimplify.cpp   | 34 +++++++++
 llvm/test/Transforms/InstCombine/select.ll  | 10 ---
 llvm/test/Transforms/InstSimplify/select.ll | 85 +++++++++++++++++++++
 3 files changed, 119 insertions(+), 10 deletions(-)
 create mode 100644 llvm/test/Transforms/InstSimplify/select.ll

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 014bc0f09ba3..3c61cd16cd53 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3055,6 +3055,40 @@ static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
   if (isa<UndefValue>(FalseVal))   // select C, X, undef -> X
     return TrueVal;
 
+  if (const auto *ICI = dyn_cast<ICmpInst>(CondVal)) {
+    Value *X;
+    const APInt *Y;
+    if (ICI->isEquality() &&
+        match(ICI->getOperand(0), m_And(m_Value(X), m_APInt(Y))) &&
+        match(ICI->getOperand(1), m_Zero())) {
+      ICmpInst::Predicate Pred = ICI->getPredicate();
+      const APInt *C;
+      // (X & Y) == 0 ? X & ~Y : X  --> X
+      // (X & Y) != 0 ? X & ~Y : X  --> X & ~Y
+      if (FalseVal == X && match(TrueVal, m_And(m_Specific(X), m_APInt(C))) &&
+          *Y == ~*C)
+        return Pred == ICmpInst::ICMP_EQ ? FalseVal : TrueVal;
+      // (X & Y) == 0 ? X : X & ~Y  --> X & ~Y
+      // (X & Y) != 0 ? X : X & ~Y  --> X
+      if (TrueVal == X && match(FalseVal, m_And(m_Specific(X), m_APInt(C))) &&
+          *Y == ~*C)
+        return Pred == ICmpInst::ICMP_EQ ? FalseVal : TrueVal;
+
+      if (Y->isPowerOf2()) {
+        // (X & Y) == 0 ? X | Y : X  --> X | Y
+        // (X & Y) != 0 ? X | Y : X  --> X
+        if (FalseVal == X && match(TrueVal, m_Or(m_Specific(X), m_APInt(C))) &&
+            *Y == *C)
+          return Pred == ICmpInst::ICMP_EQ ? TrueVal : FalseVal;
+        // (X & Y) == 0 ? X : X | Y  --> X
+        // (X & Y) != 0 ? X : X | Y  --> X | Y
+        if (TrueVal == X && match(FalseVal, m_Or(m_Specific(X), m_APInt(C))) &&
+            *Y == *C)
+          return Pred == ICmpInst::ICMP_EQ ? TrueVal : FalseVal;
+      }
+    }
+  }
+
   return nullptr;
 }
 
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 8444677d19a3..bdf48e40fd76 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -1386,13 +1386,3 @@ entry:
   %v = load i128* %p
   ret i128 %v
 }
-
-define i32 @test87(i32 %x) {
-  %and = and i32 %x, 1
-  %cmp = icmp ne i32 %and, 0
-  %and1 = and i32 %x, -2
-  %and1.x = select i1 %cmp, i32 %and1, i32 %x
-  ret i32 %and1.x
-; CHECK-LABEL: @test87(
-; CHECK: and i32 %x, -2
-}
diff --git a/llvm/test/Transforms/InstSimplify/select.ll b/llvm/test/Transforms/InstSimplify/select.ll
new file mode 100644
index 000000000000..b30416e9d265
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/select.ll
@@ -0,0 +1,85 @@
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+define i32 @test1(i32 %x) {
+  %and = and i32 %x, 1
+  %cmp = icmp eq i32 %and, 0
+  %and1 = and i32 %x, -2
+  %and1.x = select i1 %cmp, i32 %and1, i32 %x
+  ret i32 %and1.x
+; CHECK-LABEL: @test1(
+; CHECK: ret i32 %x
+}
+
+define i32 @test2(i32 %x) {
+  %and = and i32 %x, 1
+  %cmp = icmp ne i32 %and, 0
+  %and1 = and i32 %x, -2
+  %and1.x = select i1 %cmp, i32 %x, i32 %and1
+  ret i32 %and1.x
+; CHECK-LABEL: @test2(
+; CHECK: ret i32 %x
+}
+
+define i32 @test3(i32 %x) {
+  %and = and i32 %x, 1
+  %cmp = icmp ne i32 %and, 0
+  %and1 = and i32 %x, -2
+  %and1.x = select i1 %cmp, i32 %and1, i32 %x
+  ret i32 %and1.x
+; CHECK-LABEL: @test3(
+; CHECK: %[[and:.*]] = and i32 %x, -2
+; CHECK: ret i32 %[[and]]
+}
+
+; CHECK-LABEL: @select_icmp_and_8_eq_0_or_8(
+; CHECK-NEXT: [[OR:%[a-z0-9]+]] = or i32 %x, 8
+; CHECK-NEXT: ret i32 [[OR]]
+define i32 @select_icmp_and_8_eq_0_or_8(i32 %x) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %or = or i32 %x, 8
+  %or.x = select i1 %cmp, i32 %or, i32 %x
+  ret i32 %or.x
+}
+
+; CHECK-LABEL: @select_icmp_and_8_ne_0_and_not_8(
+; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %x, -9
+; CHECK-NEXT: ret i32 [[AND]]
+define i32 @select_icmp_and_8_ne_0_and_not_8(i32 %x) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %and1 = and i32 %x, -9
+  %x.and1 = select i1 %cmp, i32 %x, i32 %and1
+  ret i32 %x.and1
+}
+
+; CHECK-LABEL: @select_icmp_and_8_eq_0_and_not_8(
+; CHECK-NEXT: ret i32 %x
+define i32 @select_icmp_and_8_eq_0_and_not_8(i32 %x) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %and1 = and i32 %x, -9
+  %and1.x = select i1 %cmp, i32 %and1, i32 %x
+  ret i32 %and1.x
+}
+
+; CHECK-LABEL: @select_icmp_x_and_8_eq_0_y_and_not_8(
+; CHECK: select i1 %cmp, i64 %y, i64 %and1
+define i64 @select_icmp_x_and_8_eq_0_y_and_not_8(i32 %x, i64 %y) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %and1 = and i64 %y, -9
+  %y.and1 = select i1 %cmp, i64 %y, i64 %and1
+  ret i64 %y.and1
+}
+
+; CHECK-LABEL: @select_icmp_x_and_8_ne_0_y_and_not_8(
+; CHECK: select i1 %cmp, i64 %and1, i64 %y
+define i64 @select_icmp_x_and_8_ne_0_y_and_not_8(i32 %x, i64 %y) {
+  %and = and i32 %x, 8
+  %cmp = icmp eq i32 %and, 0
+  %and1 = and i64 %y, -9
+  %and1.y = select i1 %cmp, i64 %and1, i64 %y
+  ret i64 %and1.y
+}
+