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

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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
This commit is contained in:
Eli Friedman 2008-07-30 04:36:32 +00:00
parent 9382b9310f
commit 1fbffe0cef
2 changed files with 28 additions and 4 deletions
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8
lib/Analysis/ScalarEvolution.cpp
View File

@ -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:

24
test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll Normal file
View File

@ -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
}