From 1a601590640f6af67873bf0a72cbf4de39bad95f Mon Sep 17 00:00:00 2001
From: Chad Rosier <mcrosier@codeaurora.org>
Date: Fri, 22 Apr 2016 17:57:34 +0000
Subject: [PATCH] [SimplifyCFG] Add final missing implications to
 isImpliedTrueByMatchingCmp.

Summary: eq imply [u|s]ge and [u|s]le are true.

Remove redundant logic by implementing isImpliedFalseByMatchingCmp(Pred1, Pred2)
as isImpliedTrueByMatchingCmp(Pred1, getInversePredicate(Pred2)).

llvm-svn: 267177
---
 llvm/lib/IR/Instructions.cpp                       | 37 +++-------------------
 .../SimplifyCFG/implied-cond-matching.ll           | 16 +++++-----
 2 files changed, 13 insertions(+), 40 deletions(-)

diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index 13e5821..8ad9c07 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -3562,6 +3562,10 @@ bool CmpInst::isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
   switch (Pred1) {
   default:
     break;
+  case ICMP_EQ:
+    // A == B implies A >=u B, A <=u B, A >=u B, and A <=u B are true.
+    return Pred2 == ICMP_UGE || Pred2 == ICMP_ULE || Pred2 == ICMP_SGE ||
+           Pred2 == ICMP_SLE;
   case ICMP_UGT: // A >u B implies A != B and A >=u B are true.
     return Pred2 == ICMP_NE || Pred2 == ICMP_UGE;
   case ICMP_ULT: // A <u B implies A != B and A <=u B are true.
@@ -3575,38 +3579,7 @@ bool CmpInst::isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
 }
 
 bool CmpInst::isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2) {
-  // If an inverted Pred1 matches Pred2, we can infer the second condition is
-  // false.
-  if (getInversePredicate(Pred1) == Pred2)
-    return true;
-
-  // If a swapped Pred1 matches Pred2, we can infer the second condition is
-  // false in many cases.
-  if (getSwappedPredicate(Pred1) == Pred2) {
-    switch (Pred1) {
-    default:
-      break;
-    case ICMP_UGT: // A >u B implies A <u B is false.
-    case ICMP_ULT: // A <u B implies A >u B is false.
-    case ICMP_SGT: // A >s B implies A <s B is false.
-    case ICMP_SLT: // A <s B implies A >s B is false.
-      return true;
-    }
-  }
-  // A == B implies A > B and A < B are false.
-  if (Pred1 == ICMP_EQ && isFalseWhenEqual(Pred2))
-    return true;
-
-  switch (Pred1) {
-  default:
-    break;
-  case ICMP_UGT: // A >u B implies A == B is false.
-  case ICMP_ULT: // A <u B implies A == B is false.
-  case ICMP_SGT: // A >s B implies A == B is false.
-  case ICMP_SLT: // A <s B implies A == B is false.
-    return Pred2 == ICMP_EQ;
-  }
-  return false;
+  return isImpliedTrueByMatchingCmp(Pred1, getInversePredicate(Pred2));
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/llvm/test/Transforms/SimplifyCFG/implied-cond-matching.ll b/llvm/test/Transforms/SimplifyCFG/implied-cond-matching.ll
index e49139b..d32fd9c 100644
--- a/llvm/test/Transforms/SimplifyCFG/implied-cond-matching.ll
+++ b/llvm/test/Transforms/SimplifyCFG/implied-cond-matching.ll
@@ -140,10 +140,10 @@ untaken:
   ret void
 }
 
-; A == B implies A >=u B is unknown to be true or false.
+; A == B implies A >=u B is true.
 ; CHECK-LABEL: @test_eq_uge
 ; CHECK: call void @is(i1 true)
-; CHECK: call void @is(i1 false)
+; CHECK-NOT: call void @is(i1 false)
 define void @test_eq_uge(i32 %a, i32 %b) {
   %cmp1 = icmp eq i32 %a, %b
   br i1 %cmp1, label %taken, label %untaken
@@ -188,10 +188,10 @@ untaken:
   ret void
 }
 
-; A == B implies A <=u B is unknown to be true or false.
+; A == B implies A <=u B is true.
 ; CHECK-LABEL: @test_eq_ule
 ; CHECK: call void @is(i1 true)
-; CHECK: call void @is(i1 false)
+; CHECK-NOT: call void @is(i1 false)
 define void @test_eq_ule(i32 %a, i32 %b) {
   %cmp1 = icmp eq i32 %a, %b
   br i1 %cmp1, label %taken, label %untaken
@@ -236,10 +236,10 @@ untaken:
   ret void
 }
 
-; A == B implies A >=s B is unknown to be true or false.
+; A == B implies A >=s B is true.
 ; CHECK-LABEL: @test_eq_sge
 ; CHECK: call void @is(i1 true)
-; CHECK: call void @is(i1 false)
+; CHECK-NOT: call void @is(i1 false)
 define void @test_eq_sge(i32 %a, i32 %b) {
   %cmp1 = icmp eq i32 %a, %b
   br i1 %cmp1, label %taken, label %untaken
@@ -284,10 +284,10 @@ untaken:
   ret void
 }
 
-; A == B implies A <=s B is unknown to be true or false.
+; A == B implies A <=s B is true.
 ; CHECK-LABEL: @test_eq_sle
 ; CHECK: call void @is(i1 true)
-; CHECK: call void @is(i1 false)
+; CHECK-NOT: call void @is(i1 false)
 define void @test_eq_sle(i32 %a, i32 %b) {
   %cmp1 = icmp eq i32 %a, %b
   br i1 %cmp1, label %taken, label %untaken
-- 
2.7.4