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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.

llvm-svn: 54194
This commit is contained in:
Eli Friedman 2008-07-30 04:36:32 +00:00
parent e9a0bae238
commit 4736916aa6
2 changed files with 28 additions and 4 deletions
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8
llvm/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
llvm/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
}