[llvm] 358cdb4 - Revert "[ValueTracking] Use knownbits interface for determining if `div`/`rem` are safe to speculate"

[Noah Goldstein via llvm-commits]

Author: Noah Goldstein
Date: 2023-05-01T13:20:09-05:00
New Revision: 358cdb4489f6ce30590e9a33dceb18f7002cb83c

URL: https://github.com/llvm/llvm-project/commit/358cdb4489f6ce30590e9a33dceb18f7002cb83c
DIFF: https://github.com/llvm/llvm-project/commit/358cdb4489f6ce30590e9a33dceb18f7002cb83c.diff

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

Appears to be causing out-of-tree test failures. Reverting while the
issue is investigated.

This reverts commit fbc7fcf5ae26fad7db3e7c861fc6447e02b39cf0.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Transforms/LICM/speculate-div.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 9972a4315461f..a5259ba7fbf31 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -6035,28 +6035,29 @@ bool llvm::isSafeToSpeculativelyExecuteWithOpcode(
   case Instruction::UDiv:
   case Instruction::URem: {
     // x / y is undefined if y == 0.
-    const DataLayout &DL = Inst->getModule()->getDataLayout();
-    return isKnownNonZero(Inst->getOperand(1), DL, /*Depth*/ 0, AC, CtxI, DT);
+    const APInt *V;
+    if (match(Inst->getOperand(1), m_APInt(V)))
+      return *V != 0;
+    return false;
   }
   case Instruction::SDiv:
   case Instruction::SRem: {
     // x / y is undefined if y == 0 or x == INT_MIN and y == -1
-    const DataLayout &DL = Inst->getModule()->getDataLayout();
-    KnownBits KnownDenominator =
-        computeKnownBits(Inst->getOperand(1), DL, /*Depth*/ 0, AC, CtxI, DT);
+    const APInt *Numerator, *Denominator;
+    if (!match(Inst->getOperand(1), m_APInt(Denominator)))
+      return false;
     // We cannot hoist this division if the denominator is 0.
-    if (!KnownDenominator.isNonZero())
+    if (*Denominator == 0)
       return false;
-
     // It's safe to hoist if the denominator is not 0 or -1.
-    if (!KnownDenominator.Zero.isZero())
+    if (!Denominator->isAllOnes())
       return true;
-
-    // At this point denominator may be -1.  It is safe to hoist as
+    // At this point we know that the denominator is -1.  It is safe to hoist as
     // long we know that the numerator is not INT_MIN.
-    KnownBits KnownNumerator =
-        computeKnownBits(Inst->getOperand(0), DL, /*Depth*/ 0, AC, CtxI, DT);
-    return !KnownNumerator.getSignedMinValue().isMinSignedValue();
+    if (match(Inst->getOperand(0), m_APInt(Numerator)))
+      return !Numerator->isMinSignedValue();
+    // The numerator *might* be MinSignedValue.
+    return false;
   }
   case Instruction::Load: {
     const LoadInst *LI = dyn_cast<LoadInst>(Inst);

diff  --git a/llvm/test/Transforms/LICM/speculate-div.ll b/llvm/test/Transforms/LICM/speculate-div.ll
index e0e2c5e24dbed..50e755ef7083e 100644
--- a/llvm/test/Transforms/LICM/speculate-div.ll
+++ b/llvm/test/Transforms/LICM/speculate-div.ll
@@ -51,10 +51,10 @@ define void @sdiv_ok(i16 %n, i16 %xx) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[XO:%.*]] = or i16 [[XX:%.*]], 1
 ; CHECK-NEXT:    [[X:%.*]] = and i16 [[XO]], 123
-; CHECK-NEXT:    [[DIV:%.*]] = sdiv i16 [[N:%.*]], [[X]]
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i16 [[N:%.*]], [[X]]
 ; CHECK-NEXT:    call void @use(i16 [[DIV]])
 ; CHECK-NEXT:    br label [[LOOP]]
 ;
@@ -74,10 +74,10 @@ define void @srem_ok2(i16 %nn, i16 %xx) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[N:%.*]] = and i16 [[NN:%.*]], 123
 ; CHECK-NEXT:    [[X:%.*]] = or i16 [[XX:%.*]], 1
-; CHECK-NEXT:    [[DIV:%.*]] = srem i16 [[N]], [[X]]
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = srem i16 [[N]], [[X]]
 ; CHECK-NEXT:    call void @use(i16 [[DIV]])
 ; CHECK-NEXT:    br label [[LOOP]]
 ;
@@ -117,10 +117,10 @@ define void @udiv_ok(i16 %n, i16 %xx) {
 ; CHECK-LABEL: @udiv_ok(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[X:%.*]] = or i16 [[XX:%.*]], 1
-; CHECK-NEXT:    [[DIV:%.*]] = udiv i16 [[N:%.*]], [[X]]
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[DIV:%.*]] = udiv i16 [[N:%.*]], [[X]]
 ; CHECK-NEXT:    call void @use(i16 [[DIV]])
 ; CHECK-NEXT:    br label [[LOOP]]
 ;