[SLP]Fix compiler crash when calculating extract cost for undefs.

Need to add an extra check for potential undef values in
computeExtractCost function to avoid compiler crash on casting to
instructon.

Differential Revision: https://reviews.llvm.org/D115162

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -4348,6 +4348,10 @@ computeExtractCost(ArrayRef<Value *> VL, FixedVectorType *VecTy,
   for (auto *V : VL) {
     ++Idx;
 
+    // Need to exclude undefs from analysis.
+    if (isa<UndefValue>(V) || Mask[Idx] == UndefMaskElem)
+      continue;
+
     // Reached the start of a new vector registers.
     if (Idx % EltsPerVector == 0) {
       AllConsecutive = true;
@@ -4357,9 +4361,11 @@ computeExtractCost(ArrayRef<Value *> VL, FixedVectorType *VecTy,
     // Check all extracts for a vector register on the target directly
     // extract values in order.
     unsigned CurrentIdx = *getExtractIndex(cast<Instruction>(V));
-    unsigned PrevIdx = *getExtractIndex(cast<Instruction>(VL[Idx - 1]));
-    AllConsecutive &= PrevIdx + 1 == CurrentIdx &&
-                      CurrentIdx % EltsPerVector == Idx % EltsPerVector;
+    if (!isa<UndefValue>(VL[Idx - 1]) && Mask[Idx - 1] != UndefMaskElem) {
+      unsigned PrevIdx = *getExtractIndex(cast<Instruction>(VL[Idx - 1]));
+      AllConsecutive &= PrevIdx + 1 == CurrentIdx &&
+                        CurrentIdx % EltsPerVector == Idx % EltsPerVector;
+    }
 
     if (AllConsecutive)
       continue;

llvm/test/Transforms/SLPVectorizer/X86/extracts-with-undefs.ll

@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -slp-vectorizer -S -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+define void @test() {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[BODY:%.*]]
+; CHECK:       body:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x double> [ zeroinitializer, [[ENTRY:%.*]] ], [ zeroinitializer, [[BODY]] ]
+; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <2 x double> [[TMP0]], i32 1
+; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x double> <double poison, double undef>, double [[TMP1]], i32 0
+; CHECK-NEXT:    [[TMP3:%.*]] = fmul fast <2 x double> [[TMP2]], zeroinitializer
+; CHECK-NEXT:    [[TMP4:%.*]] = extractelement <2 x double> [[TMP3]], i32 0
+; CHECK-NEXT:    [[TMP5:%.*]] = extractelement <2 x double> [[TMP3]], i32 1
+; CHECK-NEXT:    [[ADD8_I_I:%.*]] = fadd fast double [[TMP4]], [[TMP5]]
+; CHECK-NEXT:    [[CMP42_I:%.*]] = fcmp fast ole double [[ADD8_I_I]], 0.000000e+00
+; CHECK-NEXT:    br i1 false, label [[BODY]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    br i1 false, label [[IF_THEN135_I:%.*]], label [[IF_END209_I:%.*]]
+; CHECK:       if.then135.i:
+; CHECK-NEXT:    [[TMP6:%.*]] = fcmp fast olt <2 x double> [[TMP0]], zeroinitializer
+; CHECK-NEXT:    [[TMP7:%.*]] = extractelement <2 x i1> [[TMP6]], i32 0
+; CHECK-NEXT:    [[TMP8:%.*]] = insertelement <2 x i1> <i1 poison, i1 false>, i1 [[TMP7]], i32 0
+; CHECK-NEXT:    [[TMP9:%.*]] = select <2 x i1> [[TMP8]], <2 x double> zeroinitializer, <2 x double> zeroinitializer
+; CHECK-NEXT:    [[TMP10:%.*]] = fmul fast <2 x double> zeroinitializer, [[TMP9]]
+; CHECK-NEXT:    [[TMP11:%.*]] = fmul fast <2 x double> [[TMP10]], zeroinitializer
+; CHECK-NEXT:    [[TMP12:%.*]] = fadd fast <2 x double> [[TMP11]], zeroinitializer
+; CHECK-NEXT:    br label [[IF_END209_I]]
+; CHECK:       if.end209.i:
+; CHECK-NEXT:    [[TMP13:%.*]] = phi <2 x double> [ [[TMP12]], [[IF_THEN135_I]] ], [ zeroinitializer, [[EXIT]] ]
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %body
+
+body:
+  %phi1 = phi double [ 0.000000e+00, %entry ], [ 0.000000e+00, %body ]
+  %phi2 = phi double [ 0.000000e+00, %entry ], [ 0.000000e+00, %body ]
+  %mul.i478.i = fmul fast double %phi1, 0.000000e+00
+  %mul7.i485.i = fmul fast double undef, 0.000000e+00
+  %add8.i.i = fadd fast double %mul.i478.i, %mul7.i485.i
+  %cmp42.i = fcmp fast ole double %add8.i.i, 0.000000e+00
+  br i1 false, label %body, label %exit
+
+exit:
+  br i1 false, label %if.then135.i, label %if.end209.i
+
+if.then135.i:
+  %cmp145.i = fcmp fast olt double %phi1, 0.000000e+00
+  %0 = select i1 false, double 0.000000e+00, double 0.000000e+00
+  %cmp152.i = fcmp fast olt double %phi2, 0.000000e+00
+  %1 = select i1 %cmp152.i, double 0.000000e+00, double 0.000000e+00
+  %mul166.i = fmul fast double 0.000000e+00, %0
+  %mul177.i = fmul fast double %mul166.i, 0.000000e+00
+  %add178.i = fadd fast double %mul177.i, 0.000000e+00
+  %mul181.i = fmul fast double 0.000000e+00, %1
+  %mul182.i = fmul fast double %mul181.i, 0.000000e+00
+  %add183.i = fadd fast double %mul182.i, 0.000000e+00
+  br label %if.end209.i
+
+if.end209.i:
+  %drdys.1.i = phi double [ %add183.i, %if.then135.i ], [ 0.000000e+00, %exit ]
+  %dbdxs.1.i = phi double [ %add178.i, %if.then135.i ], [ 0.000000e+00, %exit ]
+  ret void
+}