[PATCH] D44868: [SLP] Distinguish "demanded and shrinkable" from "demanded and not shrinkable" values when determining the minimum bitwidth

[Haicheng Wu via Phabricator via llvm-commits]

haicheng updated this revision to Diff 139811.
haicheng added a comment.

Rebase and update the patch.


Repository:
  rL LLVM

https://reviews.llvm.org/D44868

Files:
  lib/Transforms/Vectorize/SLPVectorizer.cpp
  test/Transforms/SLPVectorizer/AArch64/ext-trunc.ll


Index: test/Transforms/SLPVectorizer/AArch64/ext-trunc.ll
===================================================================
--- test/Transforms/SLPVectorizer/AArch64/ext-trunc.ll
+++ test/Transforms/SLPVectorizer/AArch64/ext-trunc.ll
@@ -9,9 +9,9 @@
 ; Make sure types of sub and its sources are not extended.
 ; CHECK-LABEL: @test(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[Z0:%.*]] = zext <4 x i16> [[A:%.*]] to <4 x i64>
-; CHECK-NEXT:    [[Z1:%.*]] = zext <4 x i16> [[B:%.*]] to <4 x i64>
-; CHECK-NEXT:    [[SUB0:%.*]] = sub nsw <4 x i64> [[Z0]], [[Z1]]
+; CHECK-NEXT:    [[Z0:%.*]] = zext <4 x i16> [[A:%.*]] to <4 x i32>
+; CHECK-NEXT:    [[Z1:%.*]] = zext <4 x i16> [[B:%.*]] to <4 x i32>
+; CHECK-NEXT:    [[SUB0:%.*]] = sub nsw <4 x i32> [[Z0]], [[Z1]]
 ;
 entry:
   %z0 = zext <4 x i16> %a to <4 x i32>
Index: lib/Transforms/Vectorize/SLPVectorizer.cpp
===================================================================
--- lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -4301,24 +4301,9 @@
   // additional roots that require investigating in Roots.
   SmallVector<Value *, 32> ToDemote;
   SmallVector<Value *, 4> Roots;
-  for (auto *Root : TreeRoot) {
-    // Do not include top zext/sext/trunc operations to those to be demoted, it
-    // produces noise cast<vect>, trunc <vect>, exctract <vect>, cast <extract>
-    // sequence.
-    if (isa<Constant>(Root))
-      continue;
-    auto *I = dyn_cast<Instruction>(Root);
-    if (!I || !I->hasOneUse() || !Expr.count(I))
-      return;
-    if (isa<ZExtInst>(I) || isa<SExtInst>(I))
-      continue;
-    if (auto *TI = dyn_cast<TruncInst>(I)) {
-      Roots.push_back(TI->getOperand(0));
-      continue;
-    }
+  for (auto *Root : TreeRoot)
     if (!collectValuesToDemote(Root, Expr, ToDemote, Roots))
       return;
-  }
 
   // The maximum bit width required to represent all the values that can be
   // demoted without loss of precision. It would be safe to truncate the roots
@@ -4347,7 +4332,11 @@
   // We start by looking at each entry that can be demoted. We compute the
   // maximum bit width required to store the scalar by using ValueTracking to
   // compute the number of high-order bits we can truncate.
-  if (MaxBitWidth == DL->getTypeSizeInBits(TreeRoot[0]->getType())) {
+  if (MaxBitWidth == DL->getTypeSizeInBits(TreeRoot[0]->getType()) &&
+      llvm::all_of(TreeRoot, [](Value *R) {
+        assert(R->hasOneUse() && "Root should have only one use!");
+        return isa<GetElementPtrInst>(*R->user_back());
+      })) {
     MaxBitWidth = 8u;
 
     // Determine if the sign bit of all the roots is known to be zero. If not,


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