[llvm] 4d7f3d9 - [SLP]Fix final analysis for unsigned nodes.

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2024-04-19T03:03:56-07:00
New Revision: 4d7f3d9e0fb8cf9a4db6aa73c4fcb21bae98ef3a

URL: https://github.com/llvm/llvm-project/commit/4d7f3d9e0fb8cf9a4db6aa73c4fcb21bae98ef3a
DIFF: https://github.com/llvm/llvm-project/commit/4d7f3d9e0fb8cf9a4db6aa73c4fcb21bae98ef3a.diff

LOG: [SLP]Fix final analysis for unsigned nodes.

Need to check that at least single bit is cleared for unsigned nodes
before reducing their size. Otherwise they might be treated as signed in
signed nodes.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    llvm/test/Transforms/SLPVectorizer/RISCV/unsigned-node-trunc-with-signed-users.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 075fbd3bf868f1..2e1788b83f114d 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -14442,11 +14442,19 @@ bool BoUpSLP::collectValuesToDemote(
     }
     auto NumSignBits = ComputeNumSignBits(V, *DL, 0, AC, nullptr, DT);
     unsigned BitWidth1 = OrigBitWidth - NumSignBits;
-    if (!isKnownNonNegative(V, SimplifyQuery(*DL)))
+    bool IsSigned = !isKnownNonNegative(V, SimplifyQuery(*DL));
+    if (IsSigned)
       ++BitWidth1;
     if (auto *I = dyn_cast<Instruction>(V)) {
       APInt Mask = DB->getDemandedBits(I);
-      unsigned BitWidth2 = Mask.getBitWidth() - Mask.countl_zero();
+      unsigned BitWidth2 =
+          std::max<unsigned>(1, Mask.getBitWidth() - Mask.countl_zero());
+      while (!IsSigned && BitWidth2 < OrigBitWidth) {
+        APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth2 - 1);
+        if (MaskedValueIsZero(V, Mask, SimplifyQuery(*DL)))
+          break;
+        BitWidth2 *= 2;
+      }
       BitWidth1 = std::min(BitWidth1, BitWidth2);
     }
     BitWidth = std::max(BitWidth, BitWidth1);

diff  --git a/llvm/test/Transforms/SLPVectorizer/RISCV/unsigned-node-trunc-with-signed-users.ll b/llvm/test/Transforms/SLPVectorizer/RISCV/unsigned-node-trunc-with-signed-users.ll
index 3c02817f1ac190..4f855e20fac4db 100644
--- a/llvm/test/Transforms/SLPVectorizer/RISCV/unsigned-node-trunc-with-signed-users.ll
+++ b/llvm/test/Transforms/SLPVectorizer/RISCV/unsigned-node-trunc-with-signed-users.ll
@@ -8,18 +8,20 @@ define void @test(ptr %p, i16 %load794) {
 ; CHECK-NEXT:    [[GEP799:%.*]] = getelementptr inbounds i8, ptr [[P]], i64 16
 ; CHECK-NEXT:    [[TMP1:%.*]] = load <2 x i16>, ptr [[P]], align 2
 ; CHECK-NEXT:    [[TMP2:%.*]] = load <2 x i16>, ptr [[GEP799]], align 2
-; CHECK-NEXT:    [[TMP3:%.*]] = sub <2 x i16> [[TMP2]], [[TMP1]]
-; CHECK-NEXT:    [[TMP4:%.*]] = add <2 x i16> [[TMP3]], <i16 3329, i16 3329>
+; CHECK-NEXT:    [[TMP3:%.*]] = zext <2 x i16> [[TMP1]] to <2 x i32>
+; CHECK-NEXT:    [[TMP4:%.*]] = zext <2 x i16> [[TMP2]] to <2 x i32>
+; CHECK-NEXT:    [[TMP7:%.*]] = sub nsw <2 x i32> [[TMP4]], [[TMP3]]
+; CHECK-NEXT:    [[TMP8:%.*]] = add nsw <2 x i32> [[TMP7]], <i32 3329, i32 3329>
 ; CHECK-NEXT:    [[TMP5:%.*]] = insertelement <2 x i32> poison, i32 [[ZEXT795]], i32 0
 ; CHECK-NEXT:    [[TMP6:%.*]] = shufflevector <2 x i32> [[TMP5]], <2 x i32> poison, <2 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP7:%.*]] = trunc <2 x i32> [[TMP6]] to <2 x i16>
-; CHECK-NEXT:    [[TMP8:%.*]] = mul <2 x i16> [[TMP4]], [[TMP7]]
-; CHECK-NEXT:    [[TMP9:%.*]] = zext <2 x i16> [[TMP8]] to <2 x i64>
+; CHECK-NEXT:    [[TMP12:%.*]] = mul <2 x i32> [[TMP8]], [[TMP6]]
+; CHECK-NEXT:    [[TMP9:%.*]] = zext <2 x i32> [[TMP12]] to <2 x i64>
 ; CHECK-NEXT:    [[TMP10:%.*]] = mul nuw nsw <2 x i64> [[TMP9]], <i64 5039, i64 5039>
 ; CHECK-NEXT:    [[TMP11:%.*]] = lshr <2 x i64> [[TMP10]], <i64 24, i64 24>
-; CHECK-NEXT:    [[TMP12:%.*]] = trunc <2 x i64> [[TMP11]] to <2 x i16>
-; CHECK-NEXT:    [[TMP13:%.*]] = mul <2 x i16> [[TMP12]], <i16 -3329, i16 -3329>
-; CHECK-NEXT:    [[TMP14:%.*]] = add <2 x i16> [[TMP13]], [[TMP8]]
+; CHECK-NEXT:    [[TMP13:%.*]] = trunc <2 x i64> [[TMP11]] to <2 x i32>
+; CHECK-NEXT:    [[TMP20:%.*]] = mul <2 x i32> [[TMP13]], <i32 62207, i32 62207>
+; CHECK-NEXT:    [[TMP21:%.*]] = add <2 x i32> [[TMP20]], [[TMP12]]
+; CHECK-NEXT:    [[TMP14:%.*]] = trunc <2 x i32> [[TMP21]] to <2 x i16>
 ; CHECK-NEXT:    [[TMP15:%.*]] = add <2 x i16> [[TMP14]], <i16 -3329, i16 -3329>
 ; CHECK-NEXT:    [[TMP16:%.*]] = icmp slt <2 x i16> [[TMP15]], zeroinitializer
 ; CHECK-NEXT:    [[TMP17:%.*]] = select <2 x i1> [[TMP16]], <2 x i16> [[TMP14]], <2 x i16> zeroinitializer