[ValueTracking] Use knownbits interface for determining if `div`/`rem` are safe to speculate

This just replaces the exact constant requirements with known-bits
which can prove better results.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D149423

1 files changed, 13 insertions, 14 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index a5259ba7..9972a43 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -6035,29 +6035,28 @@ bool llvm::isSafeToSpeculativelyExecuteWithOpcode(
   case Instruction::UDiv:
   case Instruction::URem: {
     // x / y is undefined if y == 0.
-    const APInt *V;
-    if (match(Inst->getOperand(1), m_APInt(V)))
-      return *V != 0;
-    return false;
+    const DataLayout &DL = Inst->getModule()->getDataLayout();
+    return isKnownNonZero(Inst->getOperand(1), DL, /*Depth*/ 0, AC, CtxI, DT);
   }
   case Instruction::SDiv:
   case Instruction::SRem: {
     // x / y is undefined if y == 0 or x == INT_MIN and y == -1
-    const APInt *Numerator, *Denominator;
-    if (!match(Inst->getOperand(1), m_APInt(Denominator)))
-      return false;
+    const DataLayout &DL = Inst->getModule()->getDataLayout();
+    KnownBits KnownDenominator =
+        computeKnownBits(Inst->getOperand(1), DL, /*Depth*/ 0, AC, CtxI, DT);
     // We cannot hoist this division if the denominator is 0.
-    if (*Denominator == 0)
+    if (!KnownDenominator.isNonZero())
       return false;
+
     // It's safe to hoist if the denominator is not 0 or -1.
-    if (!Denominator->isAllOnes())
+    if (!KnownDenominator.Zero.isZero())
       return true;
-    // At this point we know that the denominator is -1.  It is safe to hoist as
+
+    // At this point denominator may be -1.  It is safe to hoist as
     // long we know that the numerator is not INT_MIN.
-    if (match(Inst->getOperand(0), m_APInt(Numerator)))
-      return !Numerator->isMinSignedValue();
-    // The numerator *might* be MinSignedValue.
-    return false;
+    KnownBits KnownNumerator =
+        computeKnownBits(Inst->getOperand(0), DL, /*Depth*/ 0, AC, CtxI, DT);
+    return !KnownNumerator.getSignedMinValue().isMinSignedValue();
   }
   case Instruction::Load: {
     const LoadInst *LI = dyn_cast<LoadInst>(Inst);