[RLEV] Pick a correct insert point when incoming instruction is itself a phi node
This fixes https://github.com/llvm/llvm-project/issues/57336. It was exposed by a recent SCEV change, but appears to have been a long standing issue. Note that the whole insert into the loop instead of a split exit edge is slightly contrived to begin with; it's there solely because IndVarSimplify preserves the CFG. Differential Revision: https://reviews.llvm.org/D132571 (cherry picked from commit c37b1a5f764380f83ba08ae0cebca2b162123eb6)
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@ -1394,7 +1394,10 @@ int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
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// and next SCEV may errneously get smaller cost.
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// and next SCEV may errneously get smaller cost.
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// Collect all the candidate PHINodes to be rewritten.
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// Collect all the candidate PHINodes to be rewritten.
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RewritePhiSet.emplace_back(PN, i, ExitValue, Inst, HighCost);
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Instruction *InsertPt =
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(isa<PHINode>(Inst) || isa<LandingPadInst>(Inst)) ?
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&*Inst->getParent()->getFirstInsertionPt() : Inst;
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RewritePhiSet.emplace_back(PN, i, ExitValue, InsertPt, HighCost);
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}
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}
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}
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}
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}
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}
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@ -158,4 +158,42 @@ exit:
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ret i32 %phi_indvar
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ret i32 %phi_indvar
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}
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}
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define i16 @pr57336(i16 %end, i16 %m) mustprogress {
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; CHECK-LABEL: @pr57336(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[FOR_BODY:%.*]]
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; CHECK: for.body:
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; CHECK-NEXT: [[INC8:%.*]] = phi i16 [ [[INC:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
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; CHECK-NEXT: [[INC]] = add nuw nsw i16 [[INC8]], 1
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; CHECK-NEXT: [[MUL:%.*]] = mul nsw i16 [[INC8]], [[M:%.*]]
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; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp sgt i16 [[MUL]], [[END:%.*]]
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; CHECK-NEXT: br i1 [[CMP_NOT]], label [[CRIT_EDGE:%.*]], label [[FOR_BODY]]
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; CHECK: crit_edge:
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; CHECK-NEXT: [[TMP0:%.*]] = call i16 @llvm.smax.i16(i16 [[END]], i16 -1)
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; CHECK-NEXT: [[SMAX:%.*]] = add nsw i16 [[TMP0]], 1
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; CHECK-NEXT: [[TMP1:%.*]] = icmp ne i16 [[SMAX]], 0
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; CHECK-NEXT: [[UMIN:%.*]] = zext i1 [[TMP1]] to i16
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; CHECK-NEXT: [[TMP2:%.*]] = sub nsw i16 [[SMAX]], [[UMIN]]
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; CHECK-NEXT: [[UMAX:%.*]] = call i16 @llvm.umax.i16(i16 [[M]], i16 1)
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; CHECK-NEXT: [[TMP3:%.*]] = udiv i16 [[TMP2]], [[UMAX]]
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; CHECK-NEXT: [[TMP4:%.*]] = add i16 [[TMP3]], [[UMIN]]
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; CHECK-NEXT: ret i16 [[TMP4]]
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;
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entry:
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br label %for.body
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for.body:
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%inc8 = phi i16 [ %inc, %for.body ], [ 0, %entry ]
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%inc137 = phi i32 [ %inc1, %for.body ], [ 0, %entry ]
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%inc1 = add nsw i32 %inc137, 1
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%inc = add nsw i16 %inc8, 1
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%mul = mul nsw i16 %m, %inc8
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%cmp.not = icmp slt i16 %end, %mul
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br i1 %cmp.not, label %crit_edge, label %for.body
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crit_edge:
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%inc137.lcssa = phi i32 [ %inc137, %for.body ]
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%conv = trunc i32 %inc137.lcssa to i16
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ret i16 %conv
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}
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