[LV] Properly extend versioned constant strides.

We only version unknown strides to 1. If the original type is i1, then
the sign of the extension matters. Properly extend the stride value
before replacing it.

Fixes #91369.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -8841,8 +8841,10 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
       VPValue *StrideVPV = Plan->getLiveIn(U);
       if (!StrideVPV)
         continue;
-      VPValue *CI = Plan->getOrAddLiveIn(ConstantInt::get(
-          U->getType(), ScevStride->getAPInt().getSExtValue()));
+      unsigned BW = U->getType()->getScalarSizeInBits();
+      APInt C = isa<SExtInst>(U) ? ScevStride->getAPInt().sext(BW)
+                                 : ScevStride->getAPInt().zext(BW);
+      VPValue *CI = Plan->getOrAddLiveIn(ConstantInt::get(U->getType(), C));
       StrideVPV->replaceAllUsesWith(CI);
     }
   }

llvm/test/Transforms/LoopVectorize/version-stride-with-integer-casts.ll

@@ -415,7 +415,6 @@ exit:
 
 ; Test case to make sure that uses of versioned strides of type i1 are properly
 ; extended. From https://github.com/llvm/llvm-project/issues/91369.
-; FIXME: Currently miscompiled.
 define void @zext_of_i1_stride(i1 %g, ptr %dst) mustprogress {
 ; CHECK-LABEL: define void @zext_of_i1_stride(
 ; CHECK-SAME: i1 [[G:%.*]], ptr [[DST:%.*]]) #[[ATTR0:[0-9]+]] {
@@ -441,7 +440,7 @@ define void @zext_of_i1_stride(i1 %g, ptr %dst) mustprogress {
 ; CHECK-NEXT:    [[TMP3:%.*]] = add i64 [[OFFSET_IDX]], [[TMP2]]
 ; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i16, ptr [[DST]], i64 [[TMP3]]
 ; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i16, ptr [[TMP4]], i32 0
-; CHECK-NEXT:    store <4 x i16> <i16 -1, i16 -1, i16 -1, i16 -1>, ptr [[TMP5]], align 2
+; CHECK-NEXT:    store <4 x i16> <i16 1, i16 1, i16 1, i16 1>, ptr [[TMP5]], align 2
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
 ; CHECK-NEXT:    [[TMP6:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[TMP6]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP12:![0-9]+]]