[LVI] Handle implication from icmp of trunc (PR51867)

Similar to the existing urem code, if we have (trunc X) >= C,
then also X >= C.

Proof: https://alive2.llvm.org/ce/z/RF4YR2

Fixes https://github.com/llvm/llvm-project/issues/51867.

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index e095cda..e311b40 100644 (file)
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -1132,14 +1132,16 @@ static ValueLatticeElement getValueFromICmpCondition(Value *Val, ICmpInst *ICI,
   }
 
   // If (X urem Modulus) >= C, then X >= C.
+  // If trunc X >= C, then X >= C.
   // TODO: An upper bound could be computed as well.
-  if (match(LHS, m_URem(m_Specific(Val), m_Value())) &&
+  if (match(LHS, m_CombineOr(m_URem(m_Specific(Val), m_Value()),
+                             m_Trunc(m_Specific(Val)))) &&
       match(RHS, m_APInt(C))) {
     // Use the icmp region so we don't have to deal with different predicates.
     ConstantRange CR = ConstantRange::makeExactICmpRegion(EdgePred, *C);
     if (!CR.isEmptySet())
       return ValueLatticeElement::getRange(ConstantRange::getNonEmpty(
-          CR.getUnsignedMin(), APInt(BitWidth, 0)));
+          CR.getUnsignedMin().zextOrSelf(BitWidth), APInt(BitWidth, 0)));
   }
 
   return ValueLatticeElement::getOverdefined();

diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll b/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
index 5a47da8..aa1d305 100644 (file)
--- a/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
@@ -1131,14 +1131,12 @@ define void @trunc_icmp_ule(i32 %x, i1* %p) {
 ; CHECK-NEXT:    [[C:%.*]] = icmp uge i8 [[T]], 5
 ; CHECK-NEXT:    br i1 [[C]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       true:
-; CHECK-NEXT:    [[C1:%.*]] = icmp uge i32 [[X]], 5
-; CHECK-NEXT:    store i1 [[C1]], i1* [[P:%.*]], align 1
+; CHECK-NEXT:    store i1 true, i1* [[P:%.*]], align 1
 ; CHECK-NEXT:    [[C2:%.*]] = icmp ugt i32 [[X]], 5
 ; CHECK-NEXT:    store i1 [[C2]], i1* [[P]], align 1
 ; CHECK-NEXT:    [[C3:%.*]] = icmp ule i32 [[X]], 5
 ; CHECK-NEXT:    store i1 [[C3]], i1* [[P]], align 1
-; CHECK-NEXT:    [[C4:%.*]] = icmp ult i32 [[X]], 5
-; CHECK-NEXT:    store i1 [[C4]], i1* [[P]], align 1
+; CHECK-NEXT:    store i1 false, i1* [[P]], align 1
 ; CHECK-NEXT:    ret void
 ; CHECK:       false:
 ; CHECK-NEXT:    [[C1_2:%.*]] = icmp uge i32 [[X]], 5
@@ -1184,14 +1182,12 @@ define void @trunc_icmp_eq(i32 %x, i1* %p) {
 ; CHECK-NEXT:    [[C:%.*]] = icmp eq i8 [[T]], 5
 ; CHECK-NEXT:    br i1 [[C]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       true:
-; CHECK-NEXT:    [[C1:%.*]] = icmp uge i32 [[X]], 5
-; CHECK-NEXT:    store i1 [[C1]], i1* [[P:%.*]], align 1
+; CHECK-NEXT:    store i1 true, i1* [[P:%.*]], align 1
 ; CHECK-NEXT:    [[C2:%.*]] = icmp ugt i32 [[X]], 5
 ; CHECK-NEXT:    store i1 [[C2]], i1* [[P]], align 1
 ; CHECK-NEXT:    [[C3:%.*]] = icmp ule i32 [[X]], 5
 ; CHECK-NEXT:    store i1 [[C3]], i1* [[P]], align 1
-; CHECK-NEXT:    [[C4:%.*]] = icmp ult i32 [[X]], 5
-; CHECK-NEXT:    store i1 [[C4]], i1* [[P]], align 1
+; CHECK-NEXT:    store i1 false, i1* [[P]], align 1
 ; CHECK-NEXT:    ret void
 ; CHECK:       false:
 ; CHECK-NEXT:    [[C1_2:%.*]] = icmp uge i32 [[X]], 5