From 17f4bfb8d089e182b629eb26e51e6122270546b4 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Wed, 30 Aug 2017 14:04:57 +0000
Subject: [PATCH] [InstCombine] remove unnecessary vector select fold; NFCI

This code is double-dead:
1. We simplify all selects with constant true/false condition in InstSimplify.
   I've minimized/moved the tests to show that works as expected.
2. All remaining vector selects with a constant condition are canonicalized to
   shufflevector, so we really can't see this pattern.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312123 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstCombineSelect.cpp          |  4 ----
 test/Transforms/InstSimplify/compare.ll        | 18 ------------------
 test/Transforms/InstSimplify/select.ll         | 16 ++++++++++++++++
 3 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index c43dad53704..11602ab101e 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1566,10 +1566,6 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
         return replaceInstUsesWith(SI, V);
       return &SI;
     }
-
-    if (isa<ConstantAggregateZero>(CondVal)) {
-      return replaceInstUsesWith(SI, FalseVal);
-    }
   }
 
   // See if we can determine the result of this select based on a dominating
diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll
index 2fe07901916..d84e4986dbb 100644
--- a/test/Transforms/InstSimplify/compare.ll
+++ b/test/Transforms/InstSimplify/compare.ll
@@ -790,24 +790,6 @@ define i1 @non_inbounds_gep_compare2(i64* %a) {
 ; CHECK-NEXT: ret i1 true
 }
 
-define <4 x i8> @vectorselectfold(<4 x i8> %a, <4 x i8> %b) {
-  %false = icmp ne <4 x i8> zeroinitializer, zeroinitializer
-  %sel = select <4 x i1> %false, <4 x i8> %a, <4 x i8> %b
-  ret <4 x i8> %sel
-
-; CHECK-LABEL: @vectorselectfold
-; CHECK-NEXT: ret <4 x i8> %b
-}
-
-define <4 x i8> @vectorselectfold2(<4 x i8> %a, <4 x i8> %b) {
-  %true = icmp eq <4 x i8> zeroinitializer, zeroinitializer
-  %sel = select <4 x i1> %true, <4 x i8> %a, <4 x i8> %b
-  ret <4 x i8> %sel
-
-; CHECK-LABEL: @vectorselectfold
-; CHECK-NEXT: ret <4 x i8> %a
-}
-
 define i1 @compare_always_true_slt(i16 %a) {
   %1 = zext i16 %a to i32
   %2 = sub nsw i32 0, %1
diff --git a/test/Transforms/InstSimplify/select.ll b/test/Transforms/InstSimplify/select.ll
index 6044d689e2d..7ede76d4dfa 100644
--- a/test/Transforms/InstSimplify/select.ll
+++ b/test/Transforms/InstSimplify/select.ll
@@ -1,6 +1,22 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -instsimplify -S | FileCheck %s
 
+define <2 x i8> @vsel_tvec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @vsel_tvec(
+; CHECK-NEXT:    ret <2 x i8> %x
+;
+  %s = select <2 x i1><i1 true, i1 true>, <2 x i8> %x, <2 x i8> %y
+  ret <2 x i8> %s
+}
+
+define <2 x i8> @vsel_fvec(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: @vsel_fvec(
+; CHECK-NEXT:    ret <2 x i8> %y
+;
+  %s = select <2 x i1><i1 false, i1 false>, <2 x i8> %x, <2 x i8> %y
+  ret <2 x i8> %s
+}
+
 define i32 @test1(i32 %x) {
 ; CHECK-LABEL: @test1(
 ; CHECK-NEXT:    ret i32 %x
-- 
2.50.1