From 133ce871df8bc161928970216ff9b195b1fa3a14 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sat, 2 Jan 2010 00:00:03 +0000
Subject: [PATCH] Teach codegen to handle:  (X != null) | (Y != null) --> (X|Y)
 != 0  (X == null) & (Y == null) --> (X|Y) == 0

so that instcombine can stop doing this for pointers.  This is part of PR3351,
which is a case where instcombine doing this for pointers (inserting ptrtoint)
is pessimizing code.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92406 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../SelectionDAG/SelectionDAGBuilder.cpp      | 12 +++++
 test/CodeGen/X86/brcond.ll                    | 44 ++++++++++++++++++-
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 74d624f3647..40eb9eeb82a 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1195,6 +1195,18 @@ SelectionDAGBuilder::ShouldEmitAsBranches(const std::vector<CaseBlock> &Cases){
     return false;
   }
 
+  // Handle: (X != null) | (Y != null) --> (X|Y) != 0
+  // Handle: (X == null) & (Y == null) --> (X|Y) == 0
+  if (Cases[0].CmpRHS == Cases[1].CmpRHS &&
+      Cases[0].CC == Cases[1].CC &&
+      isa<Constant>(Cases[0].CmpRHS) &&
+      cast<Constant>(Cases[0].CmpRHS)->isNullValue()) {
+    if (Cases[0].CC == ISD::SETEQ && Cases[0].TrueBB == Cases[1].ThisBB)
+      return false;
+    if (Cases[0].CC == ISD::SETNE && Cases[0].FalseBB == Cases[1].ThisBB)
+      return false;
+  }
+  
   return true;
 }
 
diff --git a/test/CodeGen/X86/brcond.ll b/test/CodeGen/X86/brcond.ll
index 12674e91a0b..c0ce31c2709 100644
--- a/test/CodeGen/X86/brcond.ll
+++ b/test/CodeGen/X86/brcond.ll
@@ -1,9 +1,9 @@
 ; RUN: llc < %s -march=x86 | FileCheck %s
 ; rdar://7475489
 
-define i32 @t(i32 %a, i32 %b) nounwind ssp {
+define i32 @test1(i32 %a, i32 %b) nounwind ssp {
 entry:
-; CHECK: t:
+; CHECK: test1:
 ; CHECK: xorb
 ; CHECK-NOT: andb
 ; CHECK-NOT: shrb
@@ -27,3 +27,43 @@ bb1:                                              ; preds = %entry
 declare i32 @foo(...)
 
 declare i32 @bar(...)
+
+
+
+; PR3351 - (P == 0) & (Q == 0) -> (P|Q) == 0
+define i32 @test2(i32* %P, i32* %Q) nounwind ssp {
+entry:
+  %a = icmp eq i32* %P, null                    ; <i1> [#uses=1]
+  %b = icmp eq i32* %Q, null                    ; <i1> [#uses=1]
+  %c = and i1 %a, %b
+  br i1 %c, label %bb1, label %return
+
+bb1:                                              ; preds = %entry
+  ret i32 4
+
+return:                                           ; preds = %entry
+  ret i32 192
+; CHECK: test2:
+; CHECK:	movl	4(%esp), %eax
+; CHECK-NEXT:	orl	8(%esp), %eax
+; CHECK-NEXT:	jne	LBB2_2
+}
+
+; PR3351 - (P != 0) | (Q != 0) -> (P|Q) != 0
+define i32 @test3(i32* %P, i32* %Q) nounwind ssp {
+entry:
+  %a = icmp ne i32* %P, null                    ; <i1> [#uses=1]
+  %b = icmp ne i32* %Q, null                    ; <i1> [#uses=1]
+  %c = or i1 %a, %b
+  br i1 %c, label %bb1, label %return
+
+bb1:                                              ; preds = %entry
+  ret i32 4
+
+return:                                           ; preds = %entry
+  ret i32 192
+; CHECK: test3:
+; CHECK:	movl	4(%esp), %eax
+; CHECK-NEXT:	orl	8(%esp), %eax
+; CHECK-NEXT:	je	LBB3_2
+}