maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[IfConversion] Fix diamond conversion with unanalyzable branches. 

The code was incorrectly counting the number of identical instructions,
and therefore tried to predicate an instruction which should not have
been predicated.  This could have various effects: a compiler crash,
an assembler failure, a miscompile, or just generating an extra,
unnecessary instruction.

Instead of depending on TargetInstrInfo::removeBranch, which only
works on analyzable branches, just remove all branch instructions.

Fixes https://bugs.llvm.org/show_bug.cgi?id=43121 and
https://bugs.llvm.org/show_bug.cgi?id=41121 .

Differential Revision: https://reviews.llvm.org/D67203

llvm-svn: 371111
This commit is contained in:
Eli Friedman 2019-09-05 20:02:38 +00:00
parent 4e281f70ca
commit cae1e47f6e
2 changed files with 66 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
llvm/lib/CodeGen/IfConversion.cpp
View File

@ -1758,9 +1758,15 @@ bool IfConverter::IfConvertDiamondCommon(
if (!BBI1->IsBrAnalyzable)
verifySameBranchInstructions(&MBB1, &MBB2);
#endif
BBI1->NonPredSize -= TII->removeBranch(*BBI1->BB);
// Remove duplicated instructions.
// Remove duplicated instructions from the tail of MBB1: any branch
// instructions, and the common instructions counted by NumDups2.
DI1 = MBB1.end();
while (DI1 != MBB1.begin()) {
MachineBasicBlock::iterator Prev = std::prev(DI1);
if (!Prev->isBranch() && !Prev->isDebugInstr())
break;
DI1 = Prev;
}
for (unsigned i = 0; i != NumDups2; ) {
// NumDups2 only counted non-dbg_value instructions, so this won't
// run off the head of the list.

58
llvm/test/CodeGen/ARM/ifcvt-diamond-unanalyzable-common.mir Normal file
View File

@ -0,0 +1,58 @@
# RUN: llc %s -o - -run-pass=if-converter | FileCheck %s
# Make sure we correctly if-convert blocks containing an INLINEASM_BR.
# CHECK: t2CMPri killed renamable $r2, 34
# CHECK-NEXT: $r0 = t2MOVi 2, 1, $cpsr, $noreg
# CHECK-NEXT: $r0 = t2MOVi 3, 0, killed $cpsr, $noreg, implicit killed $r0
# CHECK-NEXT: tBL 14, $noreg, @fn2
# CHECK-NEXT: INLINEASM_BR &"", 9, 13, 0, 13, blockaddress(@fn1, %ir-block.l_yes)
# CHECK-NEXT: t2B %bb.1, 14, $noreg
--- |
target triple = "thumbv7-unknown-linux-gnueabi"
define dso_local void @fn1() {
l_yes:
ret void
}
declare dso_local i32 @fn2(...)
...
---
name: fn1
alignment: 1
tracksRegLiveness: true
body: |
bb.0:
successors: %bb.1(0x40000000), %bb.2(0x40000000)
liveins: $r0, $r1, $r2, $r4, $lr
$sp = frame-setup t2STMDB_UPD $sp, 14, $noreg, killed $r4, killed $lr
t2CMPri killed renamable $r2, 34, 14, $noreg, implicit-def $cpsr
t2Bcc %bb.2, 1, killed $cpsr
bb.1:
successors: %bb.3(0x40000000), %bb.4(0x40000000)
liveins: $r1
$r0 = t2MOVi 3, 14, $noreg, $noreg
tBL 14, $noreg, @fn2, csr_aapcs, implicit-def dead $lr, implicit $sp, implicit $r0, implicit $r1, implicit-def $sp, implicit-def dead $r0
INLINEASM_BR &"", 9, 13, 0, 13, blockaddress(@fn1, %ir-block.l_yes)
t2B %bb.3, 14, $noreg
bb.2:
successors: %bb.3(0x40000000), %bb.4(0x40000000)
liveins: $r1
$r0 = t2MOVi 2, 14, $noreg, $noreg
tBL 14, $noreg, @fn2, csr_aapcs, implicit-def dead $lr, implicit $sp, implicit $r0, implicit $r1, implicit-def $sp, implicit-def dead $r0
INLINEASM_BR &"", 9, 13, 0, 13, blockaddress(@fn1, %ir-block.l_yes)
t2B %bb.3, 14, $noreg
bb.3:
successors: %bb.4(0x80000000)
INLINEASM &"", 1
bb.4.l_yes (address-taken):
$sp = t2LDMIA_RET $sp, 14, $noreg, def $r4, def $pc
...