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Fix bug 22641 

The bug was a result of getPreStartForExtend interpreting nsw/nuw
flags on an add recurrence more strongly than is legal.  {S,+,X}<nsw>
implies S+X is nsw only if the backedge of the loop is taken at least
once.

Differential Revision: http://reviews.llvm.org/D7808

llvm-svn: 230275
This commit is contained in:
Sanjoy Das 2015-02-23 22:55:13 +00:00
parent d26f95bc94
commit 913dfd8f7f
9 changed files with 69 additions and 10 deletions
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33
llvm/lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -1063,6 +1063,34 @@ static bool canBeCheaplyTransformed(ScalarEvolution &SE,
return false;
}
static bool IsIncrementNSW(ScalarEvolution &SE, const SCEVAddRecExpr *AR) {
if (!isa<IntegerType>(AR->getType()))
return false;
unsigned BitWidth = cast<IntegerType>(AR->getType())->getBitWidth();
Type *WideTy = IntegerType::get(AR->getType()->getContext(), BitWidth * 2);
const SCEV *Step = AR->getStepRecurrence(SE);
const SCEV *OpAfterExtend = SE.getAddExpr(SE.getSignExtendExpr(Step, WideTy),
SE.getSignExtendExpr(AR, WideTy));
const SCEV *ExtendAfterOp =
SE.getSignExtendExpr(SE.getAddExpr(AR, Step), WideTy);
return ExtendAfterOp == OpAfterExtend;
}
static bool IsIncrementNUW(ScalarEvolution &SE, const SCEVAddRecExpr *AR) {
if (!isa<IntegerType>(AR->getType()))
return false;
unsigned BitWidth = cast<IntegerType>(AR->getType())->getBitWidth();
Type *WideTy = IntegerType::get(AR->getType()->getContext(), BitWidth * 2);
const SCEV *Step = AR->getStepRecurrence(SE);
const SCEV *OpAfterExtend = SE.getAddExpr(SE.getZeroExtendExpr(Step, WideTy),
SE.getZeroExtendExpr(AR, WideTy));
const SCEV *ExtendAfterOp =
SE.getZeroExtendExpr(SE.getAddExpr(AR, Step), WideTy);
return ExtendAfterOp == OpAfterExtend;
}
/// getAddRecExprPHILiterally - Helper for expandAddRecExprLiterally. Expand
/// the base addrec, which is the addrec without any non-loop-dominating
/// values, and return the PHI.
@ -1213,10 +1241,11 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
IVIncInsertPos : Pred->getTerminator();
Builder.SetInsertPoint(InsertPos);
Value *IncV = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
if (isa<OverflowingBinaryOperator>(IncV)) {
if (Normalized->getNoWrapFlags(SCEV::FlagNUW))
if (IsIncrementNUW(SE, Normalized))
cast<BinaryOperator>(IncV)->setHasNoUnsignedWrap();
if (Normalized->getNoWrapFlags(SCEV::FlagNSW))
if (IsIncrementNSW(SE, Normalized))
cast<BinaryOperator>(IncV)->setHasNoSignedWrap();
}
PN->addIncoming(IncV, Pred);

30
llvm/test/Analysis/ScalarEvolution/scev-expander-incorrect-nowrap.ll Normal file
View File

@ -0,0 +1,30 @@
; RUN: opt -indvars -S < %s | FileCheck %s
declare void @use(i32)
declare void @use.i8(i8)
define void @f() {
; CHECK-LABEL: @f
entry:
br label %loop
loop:
; The only use for idx.mirror is to induce an nuw for %idx. It does
; not induce an nuw for %idx.inc
%idx.mirror = phi i8 [ -6, %entry ], [ %idx.mirror.inc, %loop ]
%idx = phi i8 [ -5, %entry ], [ %idx.inc, %loop ]
%idx.sext = sext i8 %idx to i32
call void @use(i32 %idx.sext)
%idx.mirror.inc = add nuw i8 %idx.mirror, 1
call void @use.i8(i8 %idx.mirror.inc)
%idx.inc = add i8 %idx, 1
; CHECK-NOT: %indvars.iv.next = add nuw nsw i32 %indvars.iv, 1
%cmp = icmp ugt i8 %idx.inc, 0
br i1 %cmp, label %loop, label %exit
exit:
ret void
}

2
llvm/test/Analysis/ScalarEvolution/zext-signed-addrec.ll
View File

@ -43,7 +43,7 @@ if.end: ; preds = %if.end, %for.cond1.
%shl = and i32 %conv7, 510
store i32 %shl, i32* @c, align 4
; CHECK: %lsr.iv.next = add i32 %lsr.iv, -258
; CHECK: %lsr.iv.next = add nsw i32 %lsr.iv, -258
%dec = add i8 %2, -1
%cmp2 = icmp sgt i8 %dec, -1

2
llvm/test/CodeGen/AArch64/arm64-scaled_iv.ll
View File

@ -20,7 +20,7 @@ for.body: ; preds = %for.body, %entry
%arrayidx = getelementptr inbounds double* %b, i64 %tmp
%tmp1 = load double* %arrayidx, align 8
; The induction variable should carry the scaling factor: 1 * 8 = 8.
; CHECK: [[IVNEXT]] = add nuw i64 [[IV]], 8
; CHECK: [[IVNEXT]] = add nuw nsw i64 [[IV]], 8
%indvars.iv.next = add i64 %indvars.iv, 1
%arrayidx2 = getelementptr inbounds double* %c, i64 %indvars.iv.next
%tmp2 = load double* %arrayidx2, align 8

2
llvm/test/CodeGen/X86/avoid_complex_am.ll
View File

@ -22,7 +22,7 @@ for.body: ; preds = %for.body, %entry
%arrayidx = getelementptr inbounds double* %b, i64 %tmp
%tmp1 = load double* %arrayidx, align 8
; The induction variable should carry the scaling factor: 1.
; CHECK: [[IVNEXT]] = add nuw i64 [[IV]], 1
; CHECK: [[IVNEXT]] = add nuw nsw i64 [[IV]], 1
%indvars.iv.next = add i64 %indvars.iv, 1
%arrayidx2 = getelementptr inbounds double* %c, i64 %indvars.iv.next
%tmp2 = load double* %arrayidx2, align 8

2
llvm/test/Transforms/IndVarSimplify/overflowcheck.ll
View File

@ -9,7 +9,7 @@ target triple = "x86_64-apple-macosx"
; CHECK: @llvm.sadd.with.overflow
; CHECK-LABEL: loop2:
; CHECK-NOT: extractvalue
; CHECK: add nuw nsw
; CHECK: add nuw
; CHECK: @llvm.sadd.with.overflow
; CHECK-LABEL: loop3:
; CHECK-NOT: extractvalue

4
llvm/test/Transforms/IndVarSimplify/pr20680.ll
View File

@ -204,8 +204,8 @@ for.cond2.for.inc13_crit_edge: ; preds = %for.cond2.for.inc13
br label %for.inc13
; CHECK: [[for_inc13]]:
; CHECK-NEXT: %[[indvars_iv_next]] = add nuw nsw i32 %[[indvars_iv]], 1
; CHECK-NEXT: %[[exitcond4:.*]] = icmp ne i32 %[[indvars_iv]], -1
; CHECK-NEXT: %[[indvars_iv_next]] = add nsw i32 %[[indvars_iv]], 1
; CHECK-NEXT: %[[exitcond4:.*]] = icmp ne i32 %[[indvars_iv_next]], 0
; CHECK-NEXT: br i1 %[[exitcond4]], label %[[for_cond2_preheader]], label %[[for_end15:.*]]
for.inc13: ; preds = %for.cond2.for.inc13_crit_edge, %for.cond2.preheader
%inc14 = add i8 %storemerge15, 1

2
llvm/test/Transforms/LoopStrengthReduce/count-to-zero.ll
View File

@ -19,7 +19,7 @@ bb3: ; preds = %bb1
%tmp4 = add i32 %c_addr.1, -1 ; <i32> [#uses=1]
%c_addr.1.be = select i1 %tmp2, i32 %tmp3, i32 %tmp4 ; <i32> [#uses=1]
%indvar.next = add i32 %indvar, 1 ; <i32> [#uses=1]
; CHECK: add i32 %lsr.iv, -1
; CHECK: add nsw i32 %lsr.iv, -1
br label %bb6
bb6: ; preds = %bb3, %entry

2
llvm/test/Transforms/LoopStrengthReduce/uglygep.ll
View File

@ -59,7 +59,7 @@ bb:
; CHECK: loop0:
; Induction variable is initialized to -2.
; CHECK-NEXT: [[PHIIV:%[^ ]+]] = phi i32 [ [[IVNEXT:%[^ ]+]], %loop0 ], [ -2, %bb ]
; CHECK-NEXT: [[IVNEXT]] = add i32 [[PHIIV]], 1
; CHECK-NEXT: [[IVNEXT]] = add nuw nsw i32 [[PHIIV]], 1
; CHECK-NEXT: br i1 false, label %loop0, label %bb0
loop0: ; preds = %loop0, %bb
%i0 = phi i32 [ %i0.next, %loop0 ], [ 0, %bb ] ; <i32> [#uses=2]