[llvm-commits] [llvm] r54194 - in /llvm/trunk: lib/Analysis/ScalarEvolution.cpp test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll

[Eli Friedman]

Author: efriedma
Date: Tue Jul 29 23:36:32 2008
New Revision: 54194

URL: http://llvm.org/viewvc/llvm-project?rev=54194&view=rev
Log:
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.


Added:
    llvm/trunk/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll
Modified:
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=54194&r1=54193&r2=54194&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Tue Jul 29 23:36:32 2008
@@ -1789,10 +1789,10 @@
         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:

Added: llvm/trunk/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll?rev=54194&view=auto

==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll (added)
+++ llvm/trunk/test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll Tue Jul 29 23:36:32 2008
@@ -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
+}