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llvm-6502/test/CodeGen/ARM/2011-03-23-PeepholeBug.ll

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Cmp peephole optimization isn't always safe for signed arithmetics. int tries = INT_MAX; while (tries > 0) { tries--; } The check should be: subs r4, #1 cmp r4, #0 bgt LBB0_1 The subs can set the overflow V bit when r4 is INT_MAX+1 (which loop canonicalization apparently does in this case). cmp #0 would have cleared it while not changing the N and Z bits. Since BGT is dependent on the V bit, i.e. (N == V) && !Z, it is not safe to eliminate the cmp #0. rdar://9172742 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128179 91177308-0d34-0410-b5e6-96231b3b80d8
2011-03-23 22:52:04 +00:00
; RUN: llc < %s -mtriple=thumbv7-apple-darwin10 -relocation-model=pic -disable-fp-elim -mcpu=cortex-a8 | FileCheck %s
; subs r4, #1
; cmp r4, 0
; bgt
; cmp cannot be optimized away since it will clear the overflow bit.
; gt / ge, lt, le conditions all depend on V bit.
; rdar://9172742
define i32 @t() nounwind {
Mass update to CodeGen tests to use CHECK-LABEL for labels corresponding to function definitions for more informative error messages. No functionality change and all updated tests passed locally. This update was done with the following bash script: find test/CodeGen -name "*.ll" | \ while read NAME; do echo "$NAME" if ! grep -q "^; *RUN: *llc.*debug" $NAME; then TEMP=`mktemp -t temp` cp $NAME $TEMP sed -n "s/^define [^@]*@\([A-Za-z0-9_]*\)(.*$/\1/p" < $NAME | \ while read FUNC; do sed -i '' "s/;\(.*\)\([A-Za-z0-9_-]*\):\( *\)$FUNC: *\$/;\1\2-LABEL:\3$FUNC:/g" $TEMP done sed -i '' "s/;\(.*\)-LABEL-LABEL:/;\1-LABEL:/" $TEMP sed -i '' "s/;\(.*\)-NEXT-LABEL:/;\1-NEXT:/" $TEMP sed -i '' "s/;\(.*\)-NOT-LABEL:/;\1-NOT:/" $TEMP sed -i '' "s/;\(.*\)-DAG-LABEL:/;\1-DAG:/" $TEMP mv $TEMP $NAME fi done git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186280 91177308-0d34-0410-b5e6-96231b3b80d8
2013-07-14 06:24:09 +00:00
; CHECK-LABEL: t:
Cmp peephole optimization isn't always safe for signed arithmetics. int tries = INT_MAX; while (tries > 0) { tries--; } The check should be: subs r4, #1 cmp r4, #0 bgt LBB0_1 The subs can set the overflow V bit when r4 is INT_MAX+1 (which loop canonicalization apparently does in this case). cmp #0 would have cleared it while not changing the N and Z bits. Since BGT is dependent on the V bit, i.e. (N == V) && !Z, it is not safe to eliminate the cmp #0. rdar://9172742 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128179 91177308-0d34-0410-b5e6-96231b3b80d8
2011-03-23 22:52:04 +00:00
entry:
br label %bb2
bb: ; preds = %bb2
%0 = tail call i32 @rand() nounwind
%1 = icmp eq i32 %0, 50
br i1 %1, label %bb3, label %bb1
bb1: ; preds = %bb
%tmp = tail call i32 @puts() nounwind
%indvar.next = add i32 %indvar, 1
br label %bb2
bb2: ; preds = %bb1, %entry
; CHECK: bb2
; CHECK: subs [[REG:r[0-9]+]], #1
; CHECK: cmp [[REG]], #0
Flip the new block-placement pass to be on by default. This is mostly to test the waters. I'd like to get results from FNT build bots and other bots running on non-x86 platforms. This feature has been pretty heavily tested over the last few months by me, and it fixes several of the execution time regressions caused by the inlining work by preventing inlining decisions from radically impacting block layout. I've seen very large improvements in yacr2 and ackermann benchmarks, along with the expected noise across all of the benchmark suite whenever code layout changes. I've analyzed all of the regressions and fixed them, or found them to be impossible to fix. See my email to llvmdev for more details. I'd like for this to be in 3.1 as it complements the inliner changes, but if any failures are showing up or anyone has concerns, it is just a flag flip and so can be easily turned off. I'm switching it on tonight to try and get at least one run through various folks' performance suites in case SPEC or something else has serious issues with it. I'll watch bots and revert if anything shows up. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154816 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-16 13:49:17 +00:00
; CHECK: ble
Cmp peephole optimization isn't always safe for signed arithmetics. int tries = INT_MAX; while (tries > 0) { tries--; } The check should be: subs r4, #1 cmp r4, #0 bgt LBB0_1 The subs can set the overflow V bit when r4 is INT_MAX+1 (which loop canonicalization apparently does in this case). cmp #0 would have cleared it while not changing the N and Z bits. Since BGT is dependent on the V bit, i.e. (N == V) && !Z, it is not safe to eliminate the cmp #0. rdar://9172742 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128179 91177308-0d34-0410-b5e6-96231b3b80d8
2011-03-23 22:52:04 +00:00
%indvar = phi i32 [ %indvar.next, %bb1 ], [ 0, %entry ]
%tries.0 = sub i32 2147483647, %indvar
%tmp1 = icmp sgt i32 %tries.0, 0
br i1 %tmp1, label %bb, label %bb3
bb3: ; preds = %bb2, %bb
ret i32 0
}
declare i32 @rand()
declare i32 @puts() nounwind
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