Another SCEV issue from PR2607; essentially the same issue, but this

time applying to the implicit comparison in smin expressions. The
correct way to transform an inequality into the opposite
inequality, either signed or unsigned, is with a not expression.

I looked through the SCEV code, and I don't think there are any more
occurrences of this issue.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54194 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 14c1389b43435b83b943f13ec86564d936cf0987..bf6bc0b5dc288c2edfc43b3413cd81a66e1e9ce3 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -1789,10 +1789,10 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
         if (LHS == U->getOperand(1) && RHS == U->getOperand(2))
           return SE.getSMaxExpr(getSCEV(LHS), getSCEV(RHS));
         else if (LHS == U->getOperand(2) && RHS == U->getOperand(1))
-          // -smax(-x, -y) == smin(x, y).
-          return SE.getNegativeSCEV(SE.getSMaxExpr(
-                                        SE.getNegativeSCEV(getSCEV(LHS)),
-                                        SE.getNegativeSCEV(getSCEV(RHS))));
+          // ~smax(~x, ~y) == smin(x, y).
+          return SE.getNotSCEV(SE.getSMaxExpr(
+                                   SE.getNotSCEV(getSCEV(LHS)),
+                                   SE.getNotSCEV(getSCEV(RHS))));
         break;
       case ICmpInst::ICMP_ULT:
       case ICmpInst::ICMP_ULE:

diff --git a/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll b/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll
new file mode 100644 (file)
index 0000000..5947912
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll
@@ -0,0 +1,24 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution -disable-output \
+; RUN:   -scalar-evolution-max-iterations=0 | \
+; RUN: grep -F "( -2147483632 + ( 2147483632 smax ( -1 + ( -1 *  %x)) smax ( -1 + ( -1 *  %y)))) iterations"
+; PR2607
+
+define i32 @b(i32 %x, i32 %y) {
+entry:
+       %cmp2 = icmp slt i32 %y, %x
+       %cond3 = select i1 %cmp2, i32 %y, i32 %x
+       %cmp54 = icmp slt i32 %cond3, -2147483632
+       br i1 %cmp54, label %forinc, label %afterfor
+
+forinc:                ; preds = %forinc, %entry
+       %j.01 = phi i32 [ %dec, %forinc ], [ -2147483632, %entry ]
+       %dec = add i32 %j.01, -1
+       %cmp = icmp slt i32 %y, %x
+       %cond = select i1 %cmp, i32 %y, i32 %x
+       %cmp5 = icmp sgt i32 %dec, %cond
+       br i1 %cmp5, label %forinc, label %afterfor
+
+afterfor:              ; preds = %forinc, %entry
+       %j.0.lcssa = phi i32 [ -2147483632, %entry ], [ %dec, %forinc ]
+       ret i32 %j.0.lcssa
+}