Revert "[SLP]Do not require external uses for roots and single use for other instructions in computeMinimumValueSizes. (llvm#72679)"

This reverts commit 408dce8.

This triggered failed asserts with code like this:

    char a[];
    short *b;
    int c, d, e, f;
    void g() {
      char *h;
      for (;;) {
        for (; f; ++f) {
          h[f] = b[0] * a[e] + b[c] * a[1] >> 7;
          ++b;
        }
        h += d;
      }
    }

Compiled like this:

    $ clang -target x86_64-linux-gnu -c repro.c -O2
    clang: ../lib/IR/Instructions.cpp:3335: static llvm::CastInst* llvm::CastInst::Create(llvm::Instruction::CastOps, llvm::Value*, llvm::Type*, const llvm::Twine&, llvm::Instruction*): Assertion `castIsValid(op, S, Ty) && "Invalid cast!"' failed.

Author: mstorsjo

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -13096,14 +13096,10 @@ bool BoUpSLP::collectValuesToDemote(
   if (isa<Constant>(V))
     return true;
 
-  // If the value is not a vectorized instruction in the expression and not used
-  // by the insertelement instruction and not used in multiple vector nodes, it
-  // cannot be demoted.
+  // If the value is not a vectorized instruction in the expression with only
+  // one use, it cannot be demoted.
   auto *I = dyn_cast<Instruction>(V);
-  if (!I || !getTreeEntry(I) || MultiNodeScalars.contains(I) ||
-      !Visited.insert(I).second || all_of(I->users(), [&](User *U) {
-        return isa<InsertElementInst>(U) && !getTreeEntry(U);
-      }))
+  if (!I || !I->hasOneUse() || !getTreeEntry(I) || !Visited.insert(I).second)
     return false;
 
   unsigned Start = 0;
@@ -13174,6 +13170,11 @@ bool BoUpSLP::collectValuesToDemote(
 }
 
 void BoUpSLP::computeMinimumValueSizes() {
+  // If there are no external uses, the expression tree must be rooted by a
+  // store. We can't demote in-memory values, so there is nothing to do here.
+  if (ExternalUses.empty())
+    return;
+
   // We only attempt to truncate integer expressions.
   auto &TreeRoot = VectorizableTree[0]->Scalars;
   auto *TreeRootIT = dyn_cast<IntegerType>(TreeRoot[0]->getType());

llvm/test/Transforms/SLPVectorizer/X86/int-bitcast-minbitwidth.ll

@@ -5,14 +5,19 @@ define void @t(i64 %v) {
 ; CHECK-LABEL: define void @t(
 ; CHECK-SAME: i64 [[V:%.*]]) {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[TMP0:%.*]] = insertelement <4 x i64> poison, i64 [[V]], i32 0
-; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <4 x i64> [[TMP0]], <4 x i64> poison, <4 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP2:%.*]] = trunc <4 x i64> [[TMP1]] to <4 x i16>
-; CHECK-NEXT:    [[TMP3:%.*]] = mul <4 x i16> [[TMP2]], <i16 5, i16 6, i16 3, i16 2>
-; CHECK-NEXT:    [[TMP4:%.*]] = call i16 @llvm.vector.reduce.or.v4i16(<4 x i16> [[TMP3]])
-; CHECK-NEXT:    [[TMP5:%.*]] = sext i16 [[TMP4]] to i32
-; CHECK-NEXT:    [[TMP6:%.*]] = and i32 [[TMP5]], 65535
-; CHECK-NEXT:    store i32 [[TMP6]], ptr null, align 4
+; CHECK-NEXT:    [[CONV12_1_I:%.*]] = trunc i64 [[V]] to i32
+; CHECK-NEXT:    [[MUL_I_1_I:%.*]] = mul i32 [[CONV12_1_I]], 2
+; CHECK-NEXT:    [[CONV12_I:%.*]] = trunc i64 [[V]] to i32
+; CHECK-NEXT:    [[MUL_I_I:%.*]] = mul i32 [[CONV12_I]], 3
+; CHECK-NEXT:    [[CONV14104_I:%.*]] = or i32 [[MUL_I_1_I]], [[MUL_I_I]]
+; CHECK-NEXT:    [[CONV12_1_I_1:%.*]] = trunc i64 [[V]] to i32
+; CHECK-NEXT:    [[MUL_I_1_I_1:%.*]] = mul i32 [[CONV12_1_I_1]], 6
+; CHECK-NEXT:    [[CONV12_I_1:%.*]] = trunc i64 [[V]] to i32
+; CHECK-NEXT:    [[MUL_I_I_1:%.*]] = mul i32 [[CONV12_I_1]], 5
+; CHECK-NEXT:    [[CONV14104_I_1:%.*]] = or i32 [[MUL_I_1_I_1]], [[MUL_I_I_1]]
+; CHECK-NEXT:    [[TMP0:%.*]] = or i32 [[CONV14104_I]], [[CONV14104_I_1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[TMP0]], 65535
+; CHECK-NEXT:    store i32 [[TMP1]], ptr null, align 4
 ; CHECK-NEXT:    ret void
 ;
 entry:

llvm/test/Transforms/SLPVectorizer/X86/minbitwidth-transformed-operand.ll

@@ -5,16 +5,24 @@ define void @test(i64 %d.promoted.i) {
 ; CHECK-LABEL: define void @test(
 ; CHECK-SAME: i64 [[D_PROMOTED_I:%.*]]) {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[AND_1_I:%.*]] = and i64 0, [[D_PROMOTED_I]]
-; CHECK-NEXT:    [[AND_1_I_1:%.*]] = and i64 0, 0
-; CHECK-NEXT:    [[TMP0:%.*]] = insertelement <16 x i64> <i64 0, i64 poison, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 poison, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0>, i64 [[AND_1_I_1]], i32 1
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <16 x i64> [[TMP0]], i64 [[AND_1_I]], i32 9
-; CHECK-NEXT:    [[TMP2:%.*]] = trunc <16 x i64> [[TMP1]] to <16 x i1>
-; CHECK-NEXT:    [[TMP3:%.*]] = mul <16 x i1> [[TMP2]], zeroinitializer
-; CHECK-NEXT:    [[TMP4:%.*]] = call i1 @llvm.vector.reduce.or.v16i1(<16 x i1> [[TMP3]])
-; CHECK-NEXT:    [[TMP5:%.*]] = zext i1 [[TMP4]] to i32
-; CHECK-NEXT:    [[TMP6:%.*]] = and i32 [[TMP5]], 0
-; CHECK-NEXT:    store i32 [[TMP6]], ptr null, align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = insertelement <2 x i64> <i64 poison, i64 0>, i64 [[D_PROMOTED_I]], i32 0
+; CHECK-NEXT:    [[TMP1:%.*]] = trunc <2 x i64> [[TMP0]] to <2 x i1>
+; CHECK-NEXT:    [[TMP2:%.*]] = and <2 x i1> zeroinitializer, [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = mul <2 x i1> [[TMP2]], zeroinitializer
+; CHECK-NEXT:    [[TMP4:%.*]] = or <2 x i1> [[TMP3]], zeroinitializer
+; CHECK-NEXT:    [[TMP5:%.*]] = or <2 x i1> [[TMP4]], zeroinitializer
+; CHECK-NEXT:    [[TMP6:%.*]] = or <2 x i1> [[TMP5]], zeroinitializer
+; CHECK-NEXT:    [[TMP7:%.*]] = or <2 x i1> [[TMP6]], zeroinitializer
+; CHECK-NEXT:    [[TMP8:%.*]] = or <2 x i1> [[TMP7]], zeroinitializer
+; CHECK-NEXT:    [[TMP9:%.*]] = or <2 x i1> [[TMP8]], zeroinitializer
+; CHECK-NEXT:    [[TMP10:%.*]] = or <2 x i1> [[TMP9]], zeroinitializer
+; CHECK-NEXT:    [[TMP11:%.*]] = extractelement <2 x i1> [[TMP10]], i32 0
+; CHECK-NEXT:    [[TMP12:%.*]] = sext i1 [[TMP11]] to i32
+; CHECK-NEXT:    [[TMP13:%.*]] = extractelement <2 x i1> [[TMP10]], i32 1
+; CHECK-NEXT:    [[TMP14:%.*]] = sext i1 [[TMP13]] to i32
+; CHECK-NEXT:    [[TMP15:%.*]] = or i32 [[TMP12]], [[TMP14]]
+; CHECK-NEXT:    [[TMP16:%.*]] = and i32 [[TMP15]], 0
+; CHECK-NEXT:    store i32 [[TMP16]], ptr null, align 4
 ; CHECK-NEXT:    ret void
 ;
 entry:

llvm/test/Transforms/SLPVectorizer/X86/root-trunc-extract-reuse.ll

@@ -8,18 +8,20 @@ define i1 @test() {
 ; CHECK:       then:
 ; CHECK-NEXT:    br label [[ELSE]]
 ; CHECK:       else:
-; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i32> [ zeroinitializer, [[THEN]] ], [ zeroinitializer, [[ENTRY:%.*]] ]
-; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <2 x i32> [[TMP0]], i32 0
-; CHECK-NEXT:    [[BF_CAST162:%.*]] = and i32 [[TMP1]], 0
-; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <2 x i32> zeroinitializer, <2 x i32> [[TMP0]], <2 x i32> <i32 3, i32 1>
-; CHECK-NEXT:    [[T13:%.*]] = and <2 x i32> [[TMP2]], zeroinitializer
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i1> [ zeroinitializer, [[THEN]] ], [ zeroinitializer, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext <2 x i1> [[TMP0]] to <2 x i32>
+; CHECK-NEXT:    [[TMP2:%.*]] = extractelement <2 x i1> [[TMP0]], i32 0
+; CHECK-NEXT:    [[TMP3:%.*]] = zext i1 [[TMP2]] to i32
+; CHECK-NEXT:    [[BF_CAST162:%.*]] = and i32 [[TMP3]], 0
+; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <2 x i32> zeroinitializer, <2 x i32> [[TMP1]], <2 x i32> <i32 3, i32 1>
+; CHECK-NEXT:    [[T13:%.*]] = and <2 x i32> [[TMP4]], zeroinitializer
 ; CHECK-NEXT:    br label [[ELSE1:%.*]]
 ; CHECK:       else1:
-; CHECK-NEXT:    [[TMP3:%.*]] = shufflevector <2 x i32> [[T13]], <2 x i32> poison, <2 x i32> <i32 poison, i32 0>
-; CHECK-NEXT:    [[TMP4:%.*]] = insertelement <2 x i32> [[TMP3]], i32 [[BF_CAST162]], i32 0
-; CHECK-NEXT:    [[TMP5:%.*]] = icmp ugt <2 x i32> [[TMP4]], zeroinitializer
-; CHECK-NEXT:    [[TMP6:%.*]] = extractelement <2 x i1> [[TMP5]], i32 1
-; CHECK-NEXT:    ret i1 [[TMP6]]
+; CHECK-NEXT:    [[TMP5:%.*]] = shufflevector <2 x i32> [[T13]], <2 x i32> poison, <2 x i32> <i32 poison, i32 0>
+; CHECK-NEXT:    [[TMP6:%.*]] = insertelement <2 x i32> [[TMP5]], i32 [[BF_CAST162]], i32 0
+; CHECK-NEXT:    [[TMP7:%.*]] = icmp ugt <2 x i32> [[TMP6]], zeroinitializer
+; CHECK-NEXT:    [[TMP8:%.*]] = extractelement <2 x i1> [[TMP7]], i32 1
+; CHECK-NEXT:    ret i1 [[TMP8]]
 ;
 entry:
   br i1 false, label %then, label %else