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[IfConversion] Fix diamond conversion with unanalyzable branches.

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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 b0c1aff472
commit d4a44ed77a
2 changed files with 66 additions and 2 deletions
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10
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
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
...