From be4d7464ac98f444ea0196f53df136fcbbfb40cc Mon Sep 17 00:00:00 2001
From: Jacob Knowlton <63576748+jakeknow17@users.noreply.github.com>
Date: Tue, 10 Sep 2024 16:26:12 -0600
Subject: [PATCH] Jacob Knowlton - Assignment 2 Optimization (#58)

* Added working optimization

* Finished tests

* Added back whitespace before return

* Wrapped optimization in scope block

---------

Co-authored-by: Jacob Knowlton <u1117344@utah.edu>
---
 .../InstCombine/InstructionCombining.cpp      | 53 +++++++++++++++++++
 .../Transforms/InstCombine/mul-const-icmp.ll  | 36 +++++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 llvm/test/Transforms/InstCombine/mul-const-icmp.ll

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index c28e49f591dcd8..6606ce827fe171 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -5247,6 +5247,59 @@ Instruction* cs6475_optimizer(Instruction *I, InstCombinerImpl &IC, LazyValueInf
     }
   }
   // END JOHN REGEHR
+  
+  // BEGIN JACOB KNOWLTON
+  {
+    Value *X1 = nullptr;
+    Value *X2 = nullptr;
+    // >= case
+    ICmpInst::Predicate Pred1 = ICmpInst::ICMP_SGE; 
+    if (match(I, m_ICmp(Pred1, m_Value(X), m_Value(Y)))) {
+      if (match(Y, m_ConstantInt(C))) {
+        if (C->isZero()) {
+          if (match(X, m_Mul(m_Value(X1), m_Value(X2)))) {
+            auto Mul1 = dyn_cast<BinaryOperator>(X);
+            if (Mul1->hasNoSignedWrap()) {
+              if (match(X1, m_Mul(m_Specific(X2), m_ConstantInt(C))) || match(X1, m_Shl(m_Specific(X2), m_ConstantInt(C)))) {
+                auto Mul2 = dyn_cast<BinaryOperator>(X1);
+                if (Mul2->hasNoSignedWrap()) {
+                  if (C->getUniqueInteger().isNonNegative()) {
+                    log_optzn("Jacob Knowlton");
+                    ICmpInst::Predicate Pred3 = ICmpInst::ICMP_EQ; 
+                    return new ICmpInst(Pred3, ConstantInt::getTrue(I->getContext()), ConstantInt::getTrue(I->getContext()));
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+    // > case
+    ICmpInst::Predicate Pred2 = ICmpInst::ICMP_SGT; 
+    if (match(I, m_ICmp(Pred2, m_Value(X), m_Value(Y)))) {
+      if (match(Y, m_ConstantInt(C))) {
+        if (C->isMinusOne()) {
+          if (match(X, m_Mul(m_Value(X1), m_Value(X2)))) {
+            auto Mul1 = dyn_cast<BinaryOperator>(X);
+            if (Mul1->hasNoSignedWrap()) {
+              if (match(X1, m_Mul(m_Specific(X2), m_ConstantInt(C))) || match(X1, m_Shl(m_Specific(X2), m_ConstantInt(C)))) {
+                auto Mul2 = dyn_cast<BinaryOperator>(X1);
+                if (Mul2->hasNoSignedWrap()) {
+                  if (C->getUniqueInteger().isNonNegative()) {
+                    log_optzn("Jacob Knowlton");
+                    ICmpInst::Predicate Pred3 = ICmpInst::ICMP_EQ; 
+                    return new ICmpInst(Pred3, ConstantInt::getTrue(I->getContext()), ConstantInt::getTrue(I->getContext()));
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+  // END JACOB KNOWLTON
 
   // BEGIN BRENSEN VILLEGAS
   {
diff --git a/llvm/test/Transforms/InstCombine/mul-const-icmp.ll b/llvm/test/Transforms/InstCombine/mul-const-icmp.ll
new file mode 100644
index 00000000000000..78d7955c10e079
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/mul-const-icmp.ll
@@ -0,0 +1,36 @@
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+; Test 1: Simple Case (Optimization Applied)
+define i1 @test1(i16 %x) {
+  %mul1 = mul nsw i16 %x, 3 ; Positive constant
+  %mul2 = mul nsw i16 %mul1, %x
+  %cmp = icmp sge i16 %mul2, 0
+  ret i1 %cmp
+}
+
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:    ret i1 true
+
+; Test 2: No `nsw` Flag (Optimization Not Applied)
+define i1 @test2(i16 %x) {
+  %mul1 = mul i16 %x, 3 ; No 'nsw' flag
+  %mul2 = mul i16 %mul1, %x
+  %cmp = icmp sge i16 %mul2, 0
+  ret i1 %cmp
+}
+
+; CHECK-LABEL: @test2(
+; CHECK-NOT:    ret i1 true 
+; CHECK: ret i1 %cmp
+
+; Test 3: Non-Positive Constant (Optimization Not Applied)
+define i1 @test3(i16 %x) {
+  %mul1 = mul nsw i16 %x, -5 ; Non-positive constant
+  %mul2 = mul nsw i16 %mul1, %x
+  %cmp = icmp sge i16 %mul2, 0
+  ret i1 %cmp
+}
+
+; CHECK-LABEL: @test3(
+; CHECK-NOT:    ret i1 true
+; CHECK: ret i1 %cmp