[Polly] Fix delinearization of fortran arrays

[gareevroman]

Summary

This patch fixes processing of unsigned maximum and signed maximum operations
from r253995 and Bug 25759.

[grosser]

Hi Roman,

thanks for this patch. I only have some minor comments. I suggest you explain in the commit message briefly the issues resolved. Also, the test case could be slightly improved.

Otherwise, this LGTM. Feel free to commit after having addressed my comments.

Best,
Tobias

test/ScopDetect/scev_remove_max.ll

13 ↗

(On Diff #42989)

• Run -instnamer over the test case.
• Add a FileCheck line that ensures we actually detect the region (Otherwise we may loose this test case over time)
• Add a brief comment what is tested.

polly/trunk/lib/Analysis/ScopDetection.cpp

public:
 
   const SCEV *visitSignExtendExpr(const SCEVSignExtendExpr *Expr) {
     return SE.getSignExtendExpr(visit(Expr->getOperand()), Expr->getType());
   }
 
   const SCEV *visitUDivExpr(const SCEVUDivExpr *Expr) { return Expr; }
 
   const SCEV *visitSMaxExpr(const SCEVSMaxExpr *Expr) {
-    if (Expr->getOperand(0)->isZero()) {
+    if ((Expr->getNumOperands() == 2) and Expr->getOperand(0)->isZero()) {
       auto Res = visit(Expr->getOperand(1));
       if (Terms)
         (*Terms).push_back(Res);
       return Res;
     }
 
     return Expr;
   }
 
-  const SCEV *visitUMaxExpr(const SCEVUMaxExpr *Expr) { return visit(Expr); }
+  const SCEV *visitUMaxExpr(const SCEVUMaxExpr *Expr) { return Expr; }
 
   const SCEV *visitUnknown(const SCEVUnknown *Expr) { return Expr; }
 
   const SCEV *visitCouldNotCompute(const SCEVCouldNotCompute *Expr) {
     return Expr;
   }
 
   const SCEV *visitConstant(const SCEVConstant *Expr) { return Expr; }

polly/trunk/test/ScopDetect/scev_remove_max.ll

+; RUN: opt %loadPolly -polly-detect < %s
+
+; This test case helps to determine wether SCEVRemoveMax::remove produces
+; an infinite loop and a segmentation fault, if it processes, for exmaple,
+; '((-1 + (-1 * %b1)) umax {(-1 + (-1 * %yStart)),+,-1}<%.preheader>)'.
+;
+; In this case, the SCoP is invalid. However, SCoP detection failed when
+; running over it.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@vertPlane = external global i8*, align 8
+
+define fastcc void @Maze2Mech(i64 %i, i64 %b1, i64 %yStart) {
+.split:
+  br i1 undef, label %DrawSegment.exit, label %DrawSegment.exit34
+
+DrawSegment.exit34:                               ; preds = %.split
+  %tmp = icmp ugt i64 %yStart, %b1
+  %tmp1 = select i1 %tmp, i64 %b1, i64 %yStart
+  %tmp2 = load i8*, i8** @vertPlane, align 8
+  %y.04.i21 = add i64 %tmp1, 1
+  br label %.lr.ph.i24
+
+.lr.ph.i24:                                       ; preds = %.lr.ph.i24, %DrawSegment.exit34
+  %y.05.i22 = phi i64 [ %y.0.i23, %.lr.ph.i24 ], [ %y.04.i21, %DrawSegment.exit34 ]
+  %tmp3 = mul i64 %y.05.i22, undef
+  %tmp4 = add i64 %tmp3, %i
+  %tmp5 = getelementptr inbounds i8, i8* %tmp2, i64 %tmp4
+  %tmp6 = load i8, i8* %tmp5, align 1
+  %y.0.i23 = add nuw i64 %y.05.i22, 1
+  br i1 false, label %bb, label %.lr.ph.i24
+
+bb:                                               ; preds = %.lr.ph.i24
+  unreachable
+
+DrawSegment.exit:                                 ; preds = %.split
+  ret void
+}