[PATCH] D94869: [LV] Fix crash when computing max VF too early

[Cullen Rhodes via Phabricator via llvm-commits]

c-rhodes updated this revision to Diff 319279.
c-rhodes added a comment.

@fhahn I've simplified the test, thanks for the comments!


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D94869/new/

https://reviews.llvm.org/D94869

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/test/Transforms/LoopVectorize/Hexagon/maximum-vf-crash.ll


Index: llvm/test/Transforms/LoopVectorize/Hexagon/maximum-vf-crash.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopVectorize/Hexagon/maximum-vf-crash.ll
@@ -0,0 +1,29 @@
+; RUN: opt -march=hexagon -hexagon-autohvx -loop-vectorize -S < %s 2>&1 | FileCheck %s
+
+; Check that we don't crash.
+
+; CHECK-LABEL: @f
+; CHECK: vector.body
+
+target datalayout = "e-m:e-p:32:32:32-a:0-n16:32-i64:64:64-i32:32:32-i16:16:16-i1:8:8-f32:32:32-f64:64:64-v32:32:32-v64:64:64-v512:512:512-v1024:1024:1024-v2048:2048:2048"
+target triple = "hexagon"
+
+; Function Attrs: optsize
+define i32 @f() #0 {
+entry:
+  br label %loop
+
+loop:
+  %g.016 = phi i32 [ 0, %entry ], [ %g.1.lcssa, %loop ]
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
+  %0 = load i8, i8* undef, align 1
+  %g.1.lcssa = add i32 %g.016, undef
+  %iv.next = add nsw i32 %iv, 1
+  %exitcond = icmp eq i32 %iv.next, 0
+  br i1 %exitcond, label %exit, label %loop
+
+exit:
+  ret i32 %g.1.lcssa
+}
+
+attributes #0 = { optsize "target-features"="+hvx-length128b" }
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -5481,11 +5481,9 @@
     return None;
   }
 
-  ElementCount MaxVF = computeFeasibleMaxVF(TC, UserVF);
-
   switch (ScalarEpilogueStatus) {
   case CM_ScalarEpilogueAllowed:
-    return MaxVF;
+    return computeFeasibleMaxVF(TC, UserVF);
   case CM_ScalarEpilogueNotAllowedUsePredicate:
     LLVM_FALLTHROUGH;
   case CM_ScalarEpilogueNotNeededUsePredicate:
@@ -5523,7 +5521,7 @@
       LLVM_DEBUG(dbgs() << "LV: Cannot fold tail by masking: vectorize with a "
                            "scalar epilogue instead.\n");
       ScalarEpilogueStatus = CM_ScalarEpilogueAllowed;
-      return MaxVF;
+      return computeFeasibleMaxVF(TC, UserVF);
     }
     return None;
   }
@@ -5540,6 +5538,7 @@
     InterleaveInfo.invalidateGroupsRequiringScalarEpilogue();
   }
 
+  ElementCount MaxVF = computeFeasibleMaxVF(TC, UserVF);
   assert(!MaxVF.isScalable() &&
          "Scalable vectors do not yet support tail folding");
   assert((UserVF.isNonZero() || isPowerOf2_32(MaxVF.getFixedValue())) &&


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D94869.319279.patch
Type: text/x-patch
Size: 2314 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20210126/34447bfa/attachment.bin>