[llvm] [LVI] Add trunc to i1 handling. (PR #124480)

[Andreas Jonson via llvm-commits]

https://github.com/andjo403 updated https://github.com/llvm/llvm-project/pull/124480

>From 2947c0aab7cd8ee8d7ea462e73ffbe53716e09f7 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Sun, 26 Jan 2025 22:57:50 +0100
Subject: [PATCH] [LVI] Add trunc to i1 handling.

---
 llvm/lib/Analysis/LazyValueInfo.cpp           | 19 ++++++
 .../CorrelatedValuePropagation/icmp.ll        | 60 ++-----------------
 2 files changed, 23 insertions(+), 56 deletions(-)

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 20f69a0955f51c..05c66457fdaa3e 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -398,6 +398,8 @@ class LazyValueInfoImpl {
   std::optional<ValueLatticeElement>
   getValueFromICmpCondition(Value *Val, ICmpInst *ICI, bool isTrueDest,
                             bool UseBlockValue);
+  std::optional<ValueLatticeElement>
+  getValueFromTrunc(Value *Val, TruncInst *Trunc, bool IsTrueDest);
 
   std::optional<ValueLatticeElement>
   getValueFromCondition(Value *Val, Value *Cond, bool IsTrueDest,
@@ -1283,6 +1285,20 @@ std::optional<ValueLatticeElement> LazyValueInfoImpl::getValueFromICmpCondition(
   return ValueLatticeElement::getOverdefined();
 }
 
+std::optional<ValueLatticeElement>
+LazyValueInfoImpl::getValueFromTrunc(Value *Val, TruncInst *Trunc,
+                                     bool IsTrueDest) {
+  assert(Trunc->getType()->isIntegerTy(1));
+
+  Type *Ty = Val->getType();
+  if (!Ty->isIntegerTy() || Trunc->getOperand(0) != Val)
+    return ValueLatticeElement::getOverdefined();
+
+  if (IsTrueDest)
+    return ValueLatticeElement::getNot(Constant::getNullValue(Ty));
+  return ValueLatticeElement::getNot(Constant::getAllOnesValue(Ty));
+}
+
 // Handle conditions of the form
 // extractvalue(op.with.overflow(%x, C), 1).
 static ValueLatticeElement getValueFromOverflowCondition(
@@ -1312,6 +1328,9 @@ LazyValueInfoImpl::getValueFromCondition(Value *Val, Value *Cond,
   if (ICmpInst *ICI = dyn_cast<ICmpInst>(Cond))
     return getValueFromICmpCondition(Val, ICI, IsTrueDest, UseBlockValue);
 
+  if (auto *Trunc = dyn_cast<TruncInst>(Cond))
+    return getValueFromTrunc(Val, Trunc, IsTrueDest);
+
   if (auto *EVI = dyn_cast<ExtractValueInst>(Cond))
     if (auto *WO = dyn_cast<WithOverflowInst>(EVI->getAggregateOperand()))
       if (EVI->getNumIndices() == 1 && *EVI->idx_begin() == 1)
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
index e4de34c339d2de..d83cbf68004e88 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
@@ -1515,10 +1515,8 @@ define void @test_trunc_bittest(i8 %a) {
 ; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i8 [[A:%.*]] to i1
 ; CHECK-NEXT:    br i1 [[TRUNC]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
 ; CHECK:       if.true:
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp ne i8 [[A]], 0
-; CHECK-NEXT:    call void @check1(i1 [[CMP1]])
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i8 [[A]], 0
-; CHECK-NEXT:    call void @check1(i1 [[CMP2]])
+; CHECK-NEXT:    call void @check1(i1 true)
+; CHECK-NEXT:    call void @check1(i1 false)
 ; CHECK-NEXT:    ret void
 ; CHECK:       if.false:
 ; CHECK-NEXT:    ret void
@@ -1543,10 +1541,8 @@ define void @test_trunc_not_bittest(i8 %a) {
 ; CHECK-NEXT:    [[NOT:%.*]] = xor i1 [[TRUNC]], true
 ; CHECK-NEXT:    br i1 [[NOT]], label [[IF_FALSE:%.*]], label [[IF_TRUE:%.*]]
 ; CHECK:       if.true:
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp ne i8 [[A]], -1
-; CHECK-NEXT:    call void @check1(i1 [[CMP1]])
-; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i8 [[A]], -1
-; CHECK-NEXT:    call void @check1(i1 [[CMP2]])
+; CHECK-NEXT:    call void @check1(i1 true)
+; CHECK-NEXT:    call void @check1(i1 false)
 ; CHECK-NEXT:    ret void
 ; CHECK:       if.false:
 ; CHECK-NEXT:    ret void
@@ -1565,51 +1561,3 @@ if.true:
 if.false:
   ret void
 }
-
-define void @test_icmp_trunc(i8 %a) {
-; CHECK-LABEL: @test_icmp_trunc(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp ne i8 [[A:%.*]], 0
-; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
-; CHECK:       if.true:
-; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i8 [[A]] to i1
-; CHECK-NEXT:    call void @check1(i1 [[TRUNC]])
-; CHECK-NEXT:    ret void
-; CHECK:       if.false:
-; CHECK-NEXT:    ret void
-;
-  %cmp1 = icmp ne i8 %a, 0
-  br i1 %cmp1, label %if.true, label %if.false
-
-if.true:
-  %trunc = trunc i8 %a to i1
-  call void @check1(i1 %trunc)
-  ret void
-
-if.false:
-  ret void
-}
-
-define void @test_icmp_trunc_not(i8 %a) {
-; CHECK-LABEL: @test_icmp_trunc_not(
-; CHECK-NEXT:    [[CMP1:%.*]] = icmp eq i8 [[A:%.*]], -1
-; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
-; CHECK:       if.true:
-; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i8 [[A]] to i1
-; CHECK-NEXT:    [[NOT:%.*]] = xor i1 [[TRUNC]], true
-; CHECK-NEXT:    call void @check1(i1 [[TRUNC]])
-; CHECK-NEXT:    ret void
-; CHECK:       if.false:
-; CHECK-NEXT:    ret void
-;
-  %cmp1 = icmp eq i8 %a, -1
-  br i1 %cmp1, label %if.true, label %if.false
-
-if.true:
-  %trunc = trunc i8 %a to i1
-  %not = xor i1 %trunc, true
-  call void @check1(i1 %trunc)
-  ret void
-
-if.false:
-  ret void
-}