[ValueTracking,VectorCombine] Allow passing DT to computeConstantRange.

isValidAssumeForContext can provide better results with access to the
dominator tree in some cases. This patch adjusts computeConstantRange to
allow passing through a dominator tree.

The use VectorCombine is updated to pass through the DT to enable
additional scalarization.

Note that similar APIs like computeKnownBits already accept optional dominator
tree arguments.

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D110175

Author: fhahn

llvm/include/llvm/Analysis/ValueTracking.h

@@ -549,6 +549,7 @@ constexpr unsigned MaxAnalysisRecursionDepth = 6;
   ConstantRange computeConstantRange(const Value *V, bool UseInstrInfo = true,
                                      AssumptionCache *AC = nullptr,
                                      const Instruction *CtxI = nullptr,
+                                     const DominatorTree *DT = nullptr,
                                      unsigned Depth = 0);
 
   /// Return true if this function can prove that the instruction I will

llvm/lib/Analysis/ValueTracking.cpp

@@ -7031,6 +7031,7 @@ static void setLimitsForSelectPattern(const SelectInst &SI, APInt &Lower,
 ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo,
                                          AssumptionCache *AC,
                                          const Instruction *CtxI,
+                                         const DominatorTree *DT,
                                          unsigned Depth) {
   assert(V->getType()->isIntOrIntVectorTy() && "Expected integer instruction");
 
@@ -7069,15 +7070,15 @@ ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo,
       assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
              "must be an assume intrinsic");
 
-      if (!isValidAssumeForContext(I, CtxI, nullptr))
+      if (!isValidAssumeForContext(I, CtxI, DT))
         continue;
       Value *Arg = I->getArgOperand(0);
       ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
       // Currently we just use information from comparisons.
       if (!Cmp || Cmp->getOperand(0) != V)
         continue;
       ConstantRange RHS = computeConstantRange(Cmp->getOperand(1), UseInstrInfo,
-                                               AC, I, Depth + 1);
+                                               AC, I, DT, Depth + 1);
       CR = CR.intersectWith(
           ConstantRange::makeAllowedICmpRegion(Cmp->getPredicate(), RHS));
     }

llvm/lib/Transforms/Vectorize/VectorCombine.cpp

@@ -827,7 +827,8 @@ class ScalarizationResult {
 /// Idx. \p Idx must access a valid vector element.
 static ScalarizationResult canScalarizeAccess(FixedVectorType *VecTy,
                                               Value *Idx, Instruction *CtxI,
-                                              AssumptionCache &AC) {
+                                              AssumptionCache &AC,
+                                              const DominatorTree &DT) {
   if (auto *C = dyn_cast<ConstantInt>(Idx)) {
     if (C->getValue().ult(VecTy->getNumElements()))
       return ScalarizationResult::safe();
@@ -841,7 +842,7 @@ static ScalarizationResult canScalarizeAccess(FixedVectorType *VecTy,
   ConstantRange IdxRange(IntWidth, true);
 
   if (isGuaranteedNotToBePoison(Idx, &AC)) {
-    if (ValidIndices.contains(computeConstantRange(Idx, true, &AC, CtxI, 0)))
+    if (ValidIndices.contains(computeConstantRange(Idx, true, &AC, CtxI, &DT)))
       return ScalarizationResult::safe();
     return ScalarizationResult::unsafe();
   }
@@ -909,7 +910,7 @@ bool VectorCombine::foldSingleElementStore(Instruction &I) {
         SrcAddr != SI->getPointerOperand()->stripPointerCasts())
       return false;
 
-    auto ScalarizableIdx = canScalarizeAccess(VecTy, Idx, Load, AC);
+    auto ScalarizableIdx = canScalarizeAccess(VecTy, Idx, Load, AC, DT);
     if (ScalarizableIdx.isUnsafe() ||
         isMemModifiedBetween(Load->getIterator(), SI->getIterator(),
                              MemoryLocation::get(SI), AA))
@@ -987,7 +988,7 @@ bool VectorCombine::scalarizeLoadExtract(Instruction &I) {
     else if (LastCheckedInst->comesBefore(UI))
       LastCheckedInst = UI;
 
-    auto ScalarIdx = canScalarizeAccess(FixedVT, UI->getOperand(1), &I, AC);
+    auto ScalarIdx = canScalarizeAccess(FixedVT, UI->getOperand(1), &I, AC, DT);
     if (!ScalarIdx.isSafe()) {
       // TODO: Freeze index if it is safe to do so.
       return false;

llvm/test/Transforms/VectorCombine/AArch64/load-extract-insert-store-scalarization.ll

@@ -74,8 +74,8 @@ define void @load_extract_insert_store_var_idx_assume_valid_in_dominating_block(
 ; CHECK-NEXT:    [[MUL:%.*]] = fmul double 2.000000e+01, [[EXT_0]]
 ; CHECK-NEXT:    [[EXT_1:%.*]] = extractelement <225 x double> [[LV]], i64 [[IDX_2]]
 ; CHECK-NEXT:    [[SUB:%.*]] = fsub double [[EXT_1]], [[MUL]]
-; CHECK-NEXT:    [[INS:%.*]] = insertelement <225 x double> [[LV]], double [[SUB]], i64 [[IDX_1]]
-; CHECK-NEXT:    store <225 x double> [[INS]], <225 x double>* [[A]], align 8
+; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr inbounds <225 x double>, <225 x double>* [[A]], i64 0, i64 [[IDX_1]]
+; CHECK-NEXT:    store double [[SUB]], double* [[TMP0]], align 8
 ; CHECK-NEXT:    [[C_2:%.*]] = call i1 @cond()
 ; CHECK-NEXT:    br i1 [[C_2]], label [[LOOP]], label [[EXIT]]
 ; CHECK:       exit:

llvm/test/Transforms/VectorCombine/AArch64/load-extractelement-scalarization.ll

@@ -114,9 +114,9 @@ define i32 @load_extract_idx_var_i64_known_valid_by_assume_in_dominating_block(<
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
 ; CHECK-NEXT:    br i1 [[C_1:%.*]], label [[LOOP:%.*]], label [[EXIT:%.*]]
 ; CHECK:       loop:
-; CHECK-NEXT:    [[LV:%.*]] = load <4 x i32>, <4 x i32>* [[X:%.*]], align 16
 ; CHECK-NEXT:    call void @maythrow()
-; CHECK-NEXT:    [[R:%.*]] = extractelement <4 x i32> [[LV]], i64 [[IDX]]
+; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr inbounds <4 x i32>, <4 x i32>* [[X:%.*]], i32 0, i64 [[IDX]]
+; CHECK-NEXT:    [[R:%.*]] = load i32, i32* [[TMP0]], align 4
 ; CHECK-NEXT:    [[C_2:%.*]] = call i1 @cond()
 ; CHECK-NEXT:    br i1 [[C_2]], label [[LOOP]], label [[EXIT]]
 ; CHECK:       exit:

llvm/unittests/Analysis/ValueTrackingTest.cpp

@@ -2103,7 +2103,7 @@ TEST_F(ValueTrackingTest, ComputeConstantRange) {
 
     // Check the depth cutoff results in a conservative result (full set) by
     // passing Depth == MaxDepth == 6.
-    ConstantRange CR3 = computeConstantRange(X2, true, &AC, I, 6);
+    ConstantRange CR3 = computeConstantRange(X2, true, &AC, I, nullptr, 6);
     EXPECT_TRUE(CR3.isFullSet());
   }
   {