Limit to single unbound access. Add tests

Author: arcbbb

llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp

@@ -1777,15 +1777,9 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
   }
   // Speculative loads need to be unit-stride.
   for (LoadInst *LI : NonDerefLoads) {
-    if (LI->getParent() != TheLoop->getHeader()) {
-      reportVectorizationFailure("Cannot vectorize predicated speculative load",
-                                 "SpeculativeLoadNeedsPredication", ORE,
-                                 TheLoop);
-      return false;
-    }
     int Stride = isConsecutivePtr(LI->getType(), LI->getPointerOperand());
     if (Stride != 1) {
-      reportVectorizationFailure("Loop contains non-unit-stride load",
+      reportVectorizationFailure("Loop contains strided unbound access",
                                  "Cannot vectorize early exit loop with "
                                  "speculative non-unit-stride load",
                                  "SpeculativeNonUnitStrideLoadEarlyExitLoop",
@@ -1795,6 +1789,13 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
     SpeculativeLoads.insert(LI);
     LLVM_DEBUG(dbgs() << "LV: Found speculative load: " << *LI << "\n");
   }
+  // Support single Speculative load for now.
+  if (NonDerefLoads.size() > 1) {
+      reportVectorizationFailure("Loop contains more than one unbound access",
+                                 "TooManySpeculativeLoadInEarlyExitLoop",
+                                 ORE, TheLoop);
+      return false;
+  }
 
   [[maybe_unused]] const SCEV *SymbolicMaxBTC =
       PSE.getSymbolicMaxBackedgeTakenCount();

llvm/test/Transforms/LoopVectorize/RISCV/unbound-access-legality.ll

@@ -0,0 +1,89 @@
+; REQUIRES: asserts
+; RUN: opt -passes=loop-vectorize -debug-only=loop-vectorize -disable-output 2>&1 -mtriple=riscv64 -mattr=+v -S %s | FileCheck %s
+
+define ptr @two_unbound_access(ptr %first, ptr %last, ptr %addr2) {
+; CHECK-LABEL: LV: Checking a loop in 'two_unbound_access'
+; CHECK:       LV: Not vectorizing: Loop contains more than one unbound access.
+entry:
+  %cond = icmp eq ptr %first, %last
+  br i1 %cond, label %return, label %for.body
+
+for.body:
+  %first.addr = phi ptr [ %first, %entry], [ %first.next, %for.inc ]
+  %match.addr = phi ptr [ %addr2, %entry ], [ %match.next, %for.inc ]
+  %1 = load i32, ptr %first.addr, align 4
+  %match.value = load i32, ptr %match.addr, align 4
+  %cmp1 = icmp eq i32 %1, %match.value
+  br i1 %cmp1, label %early.exit, label %for.inc
+
+for.inc:
+  %match.next = getelementptr inbounds nuw i8, ptr %match.addr, i64 4
+  %first.next = getelementptr inbounds i8, ptr %first.addr, i64 4
+  %exit = icmp eq ptr %first.next, %last
+  br i1 %exit, label %main.exit, label %for.body
+
+early.exit:
+  br label %return
+
+main.exit:
+  br label %return
+
+return:
+  %retval = phi ptr [ %first, %entry ], [ %last, %main.exit ], [ %first.addr, %early.exit ]
+  ret ptr %retval
+}
+
+define ptr @unbound_strided_access(ptr %first, ptr %last, i32 %value) {
+; CHECK-LABEL: LV: Checking a loop in 'unbound_strided_access'
+; CHECK:       LV: Not vectorizing: Loop contains strided unbound access.
+entry:
+  %cond = icmp eq ptr %first, %last
+  br i1 %cond, label %return, label %for.body
+
+for.body:
+  %first.addr = phi ptr [ %first, %entry ], [ %first.next, %for.inc ]
+  %1 = load i32, ptr %first.addr, align 4
+  %cond2= icmp eq i32 %1, %value
+  br i1 %cond2, label %for.end, label %for.inc
+
+for.inc:
+  %first.next = getelementptr inbounds i32, ptr %first.addr, i64 2
+  %cond3 = icmp eq ptr %first.next, %last
+  br i1 %cond3, label %for.end, label %for.body
+
+for.end:
+  %retval.ph = phi ptr [ %first.addr, %for.body ], [ %last, %for.inc ]
+  br label %return
+
+return:
+  %retval = phi ptr [ %first, %entry ], [ %retval.ph, %for.end ]
+  ret ptr %retval
+}
+
+define ptr @single_unbound_access(ptr %first, ptr %last, i32 %value) {
+; CHECK-LABEL: LV: Checking a loop in 'single_unbound_access'
+; CHECK:       LV: We can vectorize this loop!
+; CHECK-NEXT:  LV: Not vectorizing: Auto-vectorization of loops with speculative load is not supported.
+entry:
+  %cond = icmp eq ptr %first, %last
+  br i1 %cond, label %return, label %for.body
+
+for.body:
+  %first.addr = phi ptr [ %first, %entry ], [ %first.next, %for.inc ]
+  %1 = load i32, ptr %first.addr, align 4
+  %cond2= icmp eq i32 %1, %value
+  br i1 %cond2, label %for.end, label %for.inc
+
+for.inc:
+  %first.next = getelementptr inbounds i32, ptr %first.addr, i64 1
+  %cond3 = icmp eq ptr %first.next, %last
+  br i1 %cond3, label %for.end, label %for.body
+
+for.end:
+  %retval.ph = phi ptr [ %first.addr, %for.body ], [ %last, %for.inc ]
+  br label %return
+
+return:
+  %retval = phi ptr [ %first, %entry ], [ %retval.ph, %for.end ]
+  ret ptr %retval
+}