Improved fix for abs(val) != 0 to check other similar case. Also fixed style issues and confusing comment

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145618 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 22 insertions, 8 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index cebe37b7b0..249de571e5 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1796,15 +1796,19 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
     return ReplaceInstUsesWith(I, V);
 
   // comparing -val or val with non-zero is the same as just comparing val
-  // ie, (val != 0) == (-val != 0)
+  // ie, abs(val) != 0 -> val != 0
   if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero()))
   {
-    Value *Cond, *SubSrc, *SelectFalse;
-    if (match(Op0, m_Select(m_Value(Cond), m_Sub(m_Zero(), m_Value(SubSrc)),
+    Value *Cond, *SelectTrue, *SelectFalse;
+    if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
                             m_Value(SelectFalse)))) {
-      if (SubSrc == SelectFalse) {
-        return CmpInst::Create(Instruction::ICmp, I.getPredicate(),
-                               SubSrc, Op1);
+      if (Value *V = dyn_castNegVal(SelectTrue)) {
+        if (V == SelectFalse)
+          return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
+      }
+      else if (Value *V = dyn_castNegVal(SelectFalse)) {
+        if (V == SelectTrue)
+          return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
       }
     }
   }
diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll
index e3d12f7fff..016e8c55fb 100644
--- a/test/Transforms/InstCombine/icmp.ll
+++ b/test/Transforms/InstCombine/icmp.ll
@@ -561,12 +561,22 @@ define i1 @test57(i32 %a) {
 }
 
 ; rdar://problem/10482509
-; CHECK: @cmpabs
+; CHECK: @cmpabs1
 ; CHECK-NEXT: icmp ne
-define zeroext i1 @cmpabs(i64 %val) {
+define zeroext i1 @cmpabs1(i64 %val) {
   %sub = sub nsw i64 0, %val
   %cmp = icmp slt i64 %val, 0
   %sub.val = select i1 %cmp, i64 %sub, i64 %val
   %tobool = icmp ne i64 %sub.val, 0
   ret i1 %tobool
 }
+
+; CHECK: @cmpabs2
+; CHECK-NEXT: icmp ne
+define zeroext i1 @cmpabs2(i64 %val) {
+  %sub = sub nsw i64 0, %val
+  %cmp = icmp slt i64 %val, 0
+  %sub.val = select i1 %cmp, i64 %val, i64 %sub
+  %tobool = icmp ne i64 %sub.val, 0
+  ret i1 %tobool
+}