[llvm] [InstructionSimplify] Convert isDivZero to range analysis (PR #100683)

[via llvm-commits]

https://github.com/AtariDreams created https://github.com/llvm/llvm-project/pull/100683

None

>From 91f5bb8a6fc74f3b673663872c9900a77d07567e Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Thu, 25 Jul 2024 22:18:43 -0400
Subject: [PATCH] [InstructionSimplify] Convert isDivZero to range analysis

---
 llvm/lib/Analysis/InstructionSimplify.cpp | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 3a7ae577bb068..bfa03e2a8f8c0 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1061,12 +1061,13 @@ static bool isDivZero(Value *X, Value *Y, const SimplifyQuery &Q,
   // IsSigned == false.
 
   // Is the unsigned dividend known to be less than a constant divisor?
-  // TODO: Convert this (and above) to range analysis
-  //      ("computeConstantRangeIncludingKnownBits")?
   const APInt *C;
-  if (match(Y, m_APInt(C)) &&
-      computeKnownBits(X, /* Depth */ 0, Q).getMaxValue().ult(*C))
-    return true;
+  if (match(Y, m_APInt(C))) {
+    ConstantRange XRange =
+        computeConstantRangeIncludingKnownBits(X, /*ForSigned=*/false, Q);
+    if (!XRange.isFullSet() && XRange.icmp(CmpInst::ICMP_ULT, *C))
+      return true;
+  }
 
   // Try again for any divisor:
   // Is the dividend unsigned less than the divisor?