[llvm] a101a9b - [SLP]Fix compiler crash when calculating extract cost for undefs.

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2021-12-06T10:46:13-08:00
New Revision: a101a9b64b31ed20e4d18c2e395b0a3742ad1836

URL: https://github.com/llvm/llvm-project/commit/a101a9b64b31ed20e4d18c2e395b0a3742ad1836
DIFF: https://github.com/llvm/llvm-project/commit/a101a9b64b31ed20e4d18c2e395b0a3742ad1836.diff

LOG: [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

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

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 335ad6c853876..06231effdac14 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/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;

diff  --git a/llvm/test/Transforms/SLPVectorizer/X86/extracts-with-undefs.ll b/llvm/test/Transforms/SLPVectorizer/X86/extracts-with-undefs.ll
new file mode 100644
index 0000000000000..a902a35d50f6b
--- /dev/null
+++ b/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
+}