[SLP] "Normal" instructions should not go between PHI and Lading pad

[ebrevnov]

Summary

Currently, SLP can insert "shuffle" instruction beween PHI and Landing pad instruction. The problem is demonstrated by LIT test. The solution is to adjust insertion point once we are done with PHI generation.

[ABataev]

LG

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

case Instruction::PHI: {
       assert(
           (E->ReorderIndices.empty() || E != VectorizableTree.front().get()) &&
           "PHI reordering is free.");
       auto *PH = cast<PHINode>(VL0);
       Builder.SetInsertPoint(PH->getParent()->getFirstNonPHI());
       Builder.SetCurrentDebugLocation(PH->getDebugLoc());
       PHINode *NewPhi = Builder.CreatePHI(VecTy, PH->getNumIncomingValues());
       Value *V = NewPhi;
+
+      // Adjust insertion point once all PHI's have been generated.
+      Builder.SetInsertPoint(&*PH->getParent()->getFirstInsertionPt());
+      Builder.SetCurrentDebugLocation(PH->getDebugLoc());
+
       ShuffleBuilder.addInversedMask(E->ReorderIndices);
       ShuffleBuilder.addMask(E->ReuseShuffleIndices);
       V = ShuffleBuilder.finalize(V);
 
       E->VectorizedValue = V;
 
       // PHINodes may have multiple entries from the same block. We want to
       // visit every block once.

llvm/test/Transforms/SLPVectorizer/X86/landing_pad.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=slp-vectorizer,verify -slp-threshold=-99999 -S | FileCheck %s
+
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @foo() personality i32* ()* @bar {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:  bb1:
+; CHECK-NEXT:    br label [[BB3:%.*]]
+; CHECK:       bb2.loopexit:
+; CHECK-NEXT:    br label [[BB2:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <4 x i32> [ [[SHUFFLE:%.*]], [[BB9:%.*]] ], [ poison, [[BB2_LOOPEXIT:%.*]] ]
+; CHECK-NEXT:    ret void
+; CHECK:       bb3:
+; CHECK-NEXT:    [[TMP1:%.*]] = phi <2 x i32> [ [[TMP5:%.*]], [[BB6:%.*]] ], [ poison, [[BB1:%.*]] ]
+; CHECK-NEXT:    [[TMP2:%.*]] = invoke i32 poison(i8 addrspace(1)* nonnull poison, i32 0, i32 0, i32 poison) [ "deopt"() ]
+; CHECK-NEXT:    to label [[BB4:%.*]] unwind label [[BB10:%.*]]
+; CHECK:       bb4:
+; CHECK-NEXT:    br i1 poison, label [[BB11:%.*]], label [[BB5:%.*]]
+; CHECK:       bb5:
+; CHECK-NEXT:    br label [[BB7:%.*]]
+; CHECK:       bb6:
+; CHECK-NEXT:    [[TMP3:%.*]] = phi <2 x i32> [ <i32 0, i32 poison>, [[BB8:%.*]] ]
+; CHECK-NEXT:    [[TMP4:%.*]] = extractelement <2 x i32> [[TMP3]], i32 1
+; CHECK-NEXT:    [[TMP5]] = insertelement <2 x i32> poison, i32 [[TMP4]], i32 1
+; CHECK-NEXT:    br label [[BB3]]
+; CHECK:       bb7:
+; CHECK-NEXT:    [[LOCAL_5_84111:%.*]] = phi i32 [ poison, [[BB8]] ], [ poison, [[BB5]] ]
+; CHECK-NEXT:    [[TMP6:%.*]] = insertelement <2 x i32> poison, i32 [[LOCAL_5_84111]], i32 1
+; CHECK-NEXT:    [[TMP7:%.*]] = invoke i32 poison(i8 addrspace(1)* nonnull poison, i32 poison, i32 poison, i32 poison) [ "deopt"() ]
+; CHECK-NEXT:    to label [[BB8]] unwind label [[BB12:%.*]]
+; CHECK:       bb8:
+; CHECK-NEXT:    br i1 poison, label [[BB7]], label [[BB6]]
+; CHECK:       bb9:
+; CHECK-NEXT:    [[INDVARS_IV528799:%.*]] = phi i64 [ poison, [[BB10]] ], [ poison, [[BB12]] ]
+; CHECK-NEXT:    [[TMP8:%.*]] = phi <2 x i32> [ [[SHUFFLE1:%.*]], [[BB10]] ], [ [[TMP11:%.*]], [[BB12]] ]
+; CHECK-NEXT:    [[TMP9:%.*]] = shufflevector <2 x i32> [[TMP8]], <2 x i32> poison, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+; CHECK-NEXT:    [[SHUFFLE]] = shufflevector <4 x i32> [[TMP9]], <4 x i32> poison, <4 x i32> <i32 undef, i32 undef, i32 0, i32 1>
+; CHECK-NEXT:    br label [[BB2]]
+; CHECK:       bb10:
+; CHECK-NEXT:    [[TMP10:%.*]] = phi <2 x i32> [ [[TMP1]], [[BB3]] ]
+; CHECK-NEXT:    [[LANDING_PAD68:%.*]] = landingpad { i8*, i32 }
+; CHECK-NEXT:    cleanup
+; CHECK-NEXT:    [[SHUFFLE1]] = shufflevector <2 x i32> [[TMP10]], <2 x i32> poison, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    br label [[BB9]]
+; CHECK:       bb11:
+; CHECK-NEXT:    ret void
+; CHECK:       bb12:
+; CHECK-NEXT:    [[TMP11]] = phi <2 x i32> [ [[TMP6]], [[BB7]] ]
+; CHECK-NEXT:    [[LANDING_PAD149:%.*]] = landingpad { i8*, i32 }
+; CHECK-NEXT:    cleanup
+; CHECK-NEXT:    br label [[BB9]]
+;
+bb1:
+  br label %bb3
+
+bb2.loopexit:
+  br label %bb2
+
+bb2:
+  %local_8_3681 = phi i32 [ poison, %bb9 ], [ 1, %bb2.loopexit ]
+  %local_2_44 = phi i32 [ poison, %bb9 ], [ poison, %bb2.loopexit ]
+  %local_5_47 = phi i32 [ %local_5_19, %bb9 ], [ poison, %bb2.loopexit ]
+  %local_10_52 = phi i32 [ %local_10_24, %bb9 ], [ poison, %bb2.loopexit ]
+  ret void
+
+bb3:
+  %local_10_38123 = phi i32 [ %.lcssa773, %bb6 ], [ poison, %bb1 ]
+  %local_5_33118 = phi i32 [ poison, %bb6 ], [ poison, %bb1 ]
+  %0 = invoke i32 poison(i8 addrspace(1)* nonnull poison, i32 0, i32 0, i32 poison) [ "deopt"() ]
+  to label %bb4 unwind label %bb10
+
+bb4:
+  br i1 poison, label %bb11, label %bb5
+
+bb5:
+  br label %bb7
+
+bb6:
+  %.lcssa773 = phi i32 [ poison, %bb8 ]
+  %.lcssa770 = phi i32 [ 0, %bb8 ]
+  br label %bb3
+
+bb7:
+  %local_5_84111 = phi i32 [ poison, %bb8 ], [ poison, %bb5 ]
+  %1 = invoke i32 poison(i8 addrspace(1)* nonnull poison, i32 poison, i32 poison, i32 poison) [ "deopt"() ]
+  to label %bb8 unwind label %bb12
+
+bb8:
+  br i1 poison, label %bb7, label %bb6
+
+bb9:
+  %indvars.iv528799 = phi i64 [ poison, %bb10 ], [ poison, %bb12 ]
+  %local_5_19 = phi i32 [ %local_5_33118.lcssa, %bb10 ], [ %local_5_84111.lcssa, %bb12 ]
+  %local_10_24 = phi i32 [ %local_10_38123.lcssa, %bb10 ], [ %local_10_89113.lcssa, %bb12 ]
+  br label %bb2
+
+bb10:
+  %local_10_38123.lcssa = phi i32 [ %local_10_38123, %bb3 ]
+  %local_5_33118.lcssa = phi i32 [ %local_5_33118, %bb3 ]
+  %landing_pad68 = landingpad { i8*, i32 }
+  cleanup
+  br label %bb9
+
+bb11:
+  ret void
+
+bb12:
+  %local_10_89113.lcssa = phi i32 [ poison, %bb7 ]
+  %local_5_84111.lcssa = phi i32 [ %local_5_84111, %bb7 ]
+  %landing_pad149 = landingpad { i8*, i32 }
+  cleanup
+  br label %bb9
+}
+
+declare i32* @bar()
+
+