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PR17473:

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Don't normalize an expression during postinc transformation unless it's
invertible.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203719 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Zolotukhin 2014-03-12 21:31:05 +00:00
parent a65ca9dcf0
commit 4a0593ccd3
2 changed files with 88 additions and 3 deletions
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24
lib/Analysis/IVUsers.cpp
View File

@ -12,7 +12,6 @@
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "iv-users"
#include "llvm/Analysis/IVUsers.h"
#include "llvm/ADT/STLExtras.h"
@ -186,15 +185,34 @@ bool IVUsers::AddUsersImpl(Instruction *I,
if (AddUserToIVUsers) {
// Okay, we found a user that we cannot reduce.
IVUses.push_back(new IVStrideUse(this, User, I));
IVStrideUse &NewUse = IVUses.back();
IVStrideUse &NewUse = AddUser(User, I);
// Autodetect the post-inc loop set, populating NewUse.PostIncLoops.
// The regular return value here is discarded; instead of recording
// it, we just recompute it when we need it.
const SCEV *OriginalISE = ISE;
ISE = TransformForPostIncUse(NormalizeAutodetect,
ISE, User, I,
NewUse.PostIncLoops,
*SE, *DT);
// PostIncNormalization effectively simplifies the expression under
// pre-increment assumptions. Those assumptions (no wrapping) might not
// hold for the post-inc value. Catch such cases by making sure the
// transformation is invertible.
if (OriginalISE != ISE) {
const SCEV *DenormalizedISE =
TransformForPostIncUse(Denormalize, ISE, User, I,
NewUse.PostIncLoops, *SE, *DT);
// If we normalized the expression, but denormalization doesn't give the
// original one, discard this user.
if (OriginalISE != DenormalizedISE) {
DEBUG(dbgs() << " DISCARDING (NORMALIZATION ISN'T INVERTIBLE): "
<< *ISE << '\n');
IVUses.pop_back();
return false;
}
}
DEBUG(if (SE->getSCEV(I) != ISE)
dbgs() << " NORMALIZED TO: " << *ISE << '\n');
}

67
test/Transforms/LoopStrengthReduce/pr17473.ll Normal file
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@ -0,0 +1,67 @@
; RUN: opt < %s -loop-reduce -S | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.9.0"
; LSR shouldn't normalize IV if it can't be denormalized to the original
; expression. In this testcase, the normalized expression was denormalized to
; an expression different from the original, and we were losing sign extension.
; CHECK: [[TMP:%[a-z]+]] = trunc i32 {{.*}} to i8
; CHECK: {{%[a-z0-9]+}} = sext i8 [[TMP]] to i32
@j = common global i32 0, align 4
@c = common global i32 0, align 4
@g = common global i32 0, align 4
@h = common global i8 0, align 1
@d = common global i32 0, align 4
@i = common global i32 0, align 4
@e = common global i32 0, align 4
@.str = private unnamed_addr constant [4 x i8] c"%x\0A\00", align 1
@a = common global i32 0, align 4
@b = common global i16 0, align 2
; Function Attrs: nounwind optsize ssp uwtable
define i32 @main() #0 {
entry:
store i8 0, i8* @h, align 1
%0 = load i32* @j, align 4
%tobool.i = icmp eq i32 %0, 0
%1 = load i32* @d, align 4
%cmp3 = icmp sgt i32 %1, -1
%.lobit = lshr i32 %1, 31
%.lobit.not = xor i32 %.lobit, 1
br label %for.body
for.body: ; preds = %entry, %fn3.exit
%inc9 = phi i8 [ 0, %entry ], [ %inc, %fn3.exit ]
%conv = sext i8 %inc9 to i32
br i1 %tobool.i, label %fn3.exit, label %land.rhs.i
land.rhs.i: ; preds = %for.body
store i32 0, i32* @c, align 4
br label %fn3.exit
fn3.exit: ; preds = %for.body, %land.rhs.i
%inc = add i8 %inc9, 1
%cmp = icmp sgt i8 %inc, -1
br i1 %cmp, label %for.body, label %for.end
for.end: ; preds = %fn3.exit
%.lobit.not. = select i1 %cmp3, i32 %.lobit.not, i32 0
store i32 %conv, i32* @g, align 4
store i32 %.lobit.not., i32* @i, align 4
store i8 %inc, i8* @h, align 1
%conv7 = sext i8 %inc to i32
%add = add nsw i32 %conv7, %conv
store i32 %add, i32* @e, align 4
%call = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i32 %add) #2
ret i32 0
}
; Function Attrs: nounwind optsize
declare i32 @printf(i8* nocapture readonly, ...) #1
attributes #0 = { nounwind optsize ssp uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind optsize "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind optsize }