[llvm] e1e20c0 - [SLP]Fix bitwidth analysis for signed nodes, incoming into UITOFP nodes

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2025-02-28T11:50:50-08:00
New Revision: e1e20c07e48b135c9f9118797f25679132702aea

URL: https://github.com/llvm/llvm-project/commit/e1e20c07e48b135c9f9118797f25679132702aea
DIFF: https://github.com/llvm/llvm-project/commit/e1e20c07e48b135c9f9118797f25679132702aea.diff

LOG: [SLP]Fix bitwidth analysis for signed nodes, incoming into UITOFP nodes

If the signed node is the operand of UITOFP, the bitwidth analysis
should consider minimum value between incoming bitwidth and the bitwidth
of the UITOFP node.

Fixes #129244

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    llvm/test/Transforms/SLPVectorizer/X86/uitofp-with-signed-value-bitwidth.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 2d343ca31f07b..4a68e0ee5989c 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -18423,6 +18423,14 @@ void BoUpSLP::computeMinimumValueSizes() {
       return Known.isNonNegative();
     });
 
+    if (!IsKnownPositive && !IsTopRoot && E.UserTreeIndex &&
+        E.UserTreeIndex.UserTE->hasState() &&
+        E.UserTreeIndex.UserTE->getOpcode() == Instruction::UIToFP)
+      MaxBitWidth =
+          std::min(DL->getTypeSizeInBits(
+                       E.UserTreeIndex.UserTE->Scalars.front()->getType()),
+                   DL->getTypeSizeInBits(ScalarTy));
+
     // We first check if all the bits of the roots are demanded. If they're not,
     // we can truncate the roots to this narrower type.
     for (Value *Root : E.Scalars) {

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/uitofp-with-signed-value-bitwidth.ll b/llvm/test/Transforms/SLPVectorizer/X86/uitofp-with-signed-value-bitwidth.ll
index de6140f75424b..9f0e8bc6bfa37 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/uitofp-with-signed-value-bitwidth.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/uitofp-with-signed-value-bitwidth.ll
@@ -7,7 +7,8 @@ define i32 @test(ptr %d, i32 %0) {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
 ; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x i32> poison, i32 [[TMP0]], i32 0
 ; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <2 x i32> [[TMP1]], <2 x i32> poison, <2 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP3:%.*]] = uitofp <2 x i32> [[TMP2]] to <2 x double>
+; CHECK-NEXT:    [[TMP8:%.*]] = sext <2 x i32> [[TMP2]] to <2 x i64>
+; CHECK-NEXT:    [[TMP3:%.*]] = uitofp <2 x i64> [[TMP8]] to <2 x double>
 ; CHECK-NEXT:    [[TMP4:%.*]] = fdiv <2 x double> [[TMP3]], zeroinitializer
 ; CHECK-NEXT:    [[TMP5:%.*]] = fcmp ogt <2 x double> [[TMP4]], zeroinitializer
 ; CHECK-NEXT:    [[TMP6:%.*]] = extractelement <2 x i1> [[TMP5]], i32 1