[llvm-bugs] [Bug 45557] New: Bad machine code: PHI operand is not live-out from predecessor

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45557

            Bug ID: 45557
           Summary: Bad machine code: PHI operand is not live-out from
                    predecessor
           Product: libraries
           Version: 10.0
          Hardware: Other
                OS: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: PowerPC
          Assignee: unassignedbugs at nondot.org
          Reporter: pkubaj at anongoth.pl
                CC: llvm-bugs at lists.llvm.org, nemanja.i.ibm at gmail.com

FreeBSD head, LLVM 10.0.0, powerpc architecture (32-bit)

Reduced test case:
a, b;
c() {
  int d;
  int e[] = {0, &a};
  if (b)
    e[0] = f();
  d = 0;
  for (; d < 2; d++)
    if (e[d])
      g();
}

Compile with:
/usr/bin/cc -cc1 -triple powerpc-unknown-freebsd13.0 -emit-obj -O2
-mrelocation-model static -x c pbx_variables-3bff13.c

Problem:
# Machine code for function c: IsSSA, TracksLiveness

bb.0.entry:
  successors: %bb.2(0x30000000), %bb.1(0x50000000); %bb.2(37.50%),
%bb.1(62.50%)

  %4:gprc_and_gprc_nor0 = LIS target-flags(ppc-ha) @__const.c.e
  %6:gprc_and_gprc_nor0 = LIS target-flags(ppc-ha) @b
  %7:gprc = LWZ target-flags(ppc-lo) @b, killed %6:gprc_and_gprc_nor0 ::
(dereferenceable load 4 from @b, !tbaa !2)
  %8:crrc = CMPLWI killed %7:gprc, 0
  BCC 76, killed %8:crrc, %bb.2
  B %bb.1

bb.1.if.then:
; predecessors: %bb.0
  successors: %bb.2(0x80000000); %bb.2(100.00%)

  ADJCALLSTACKDOWN 8, 0, implicit-def dead $r1, implicit $r1
  BL @f, <regmask $cr2 $cr3 $cr4 $f14 $f15 $f16 $f17 $f18 $f19 $f20 $f21 $f22
$f23 $f24 $f25 $f26 $f27 $f28 $f29 $f30 $f31 $r14 $r15 $r16 $r17 $r18 $r19 $r20
$r21 $r22 $r23 $r24 $r25 and 18 more...>, implicit-def dead $lr, implicit $rm,
implicit-def $r1, implicit-def $r3
  ADJCALLSTACKUP 8, 0, implicit-def dead $r1, implicit $r1
  %9:gprc = COPY $r3
  %2:gprc = COPY %9:gprc

bb.2.if.end:
; predecessors: %bb.0, %bb.1
  successors: %bb.4(0x30000000), %bb.3(0x50000000); %bb.4(37.50%),
%bb.3(62.50%)

  %3:gprc = PHI %0:gprc, %bb.0, %2:gprc, %bb.1
  %0:gprc, %5:gprc_and_gprc_nor0 = LWZU target-flags(ppc-lo) @__const.c.e,
%4:gprc_and_gprc_nor0(tied-def 1) :: (load 4 from `i64* bitcast ([2 x i32]*
@__const.c.e to i64*)`, align 8)
  %1:gprc = LWZ 4, %5:gprc_and_gprc_nor0 :: (dereferenceable load 4 from `i64*
bitcast ([2 x i32]* @__const.c.e to i64*)` + 4)
  %10:crrc = CMPLWI %3:gprc, 0
  BCC 76, killed %10:crrc, %bb.4
  B %bb.3

bb.3.if.then3:
; predecessors: %bb.2
  successors: %bb.4(0x80000000); %bb.4(100.00%)

  ADJCALLSTACKDOWN 8, 0, implicit-def dead $r1, implicit $r1
  BL @g, <regmask $cr2 $cr3 $cr4 $f14 $f15 $f16 $f17 $f18 $f19 $f20 $f21 $f22
$f23 $f24 $f25 $f26 $f27 $f28 $f29 $f30 $f31 $r14 $r15 $r16 $r17 $r18 $r19 $r20
$r21 $r22 $r23 $r24 $r25 and 18 more...>, implicit-def dead $lr, implicit $rm,
implicit-def $r1, implicit-def $r3
  ADJCALLSTACKUP 8, 0, implicit-def dead $r1, implicit $r1

bb.4.for.inc:
; predecessors: %bb.2, %bb.3
  successors: %bb.6(0x30000000), %bb.5(0x50000000); %bb.6(37.50%),
%bb.5(62.50%)

  %12:crrc = CMPLWI %1:gprc, 0
  BCC 76, killed %12:crrc, %bb.6
  B %bb.5

bb.5.if.then3.1:
; predecessors: %bb.4
  successors: %bb.6(0x80000000); %bb.6(100.00%)

  ADJCALLSTACKDOWN 8, 0, implicit-def dead $r1, implicit $r1
  BL @g, <regmask $cr2 $cr3 $cr4 $f14 $f15 $f16 $f17 $f18 $f19 $f20 $f21 $f22
$f23 $f24 $f25 $f26 $f27 $f28 $f29 $f30 $f31 $r14 $r15 $r16 $r17 $r18 $r19 $r20
$r21 $r22 $r23 $r24 $r25 and 18 more...>, implicit-def dead $lr, implicit $rm,
implicit-def $r1, implicit-def $r3
  ADJCALLSTACKUP 8, 0, implicit-def dead $r1, implicit $r1

bb.6.for.inc.1:
; predecessors: %bb.4, %bb.5

  %14:gprc = IMPLICIT_DEF
  $r3 = COPY %14:gprc
  BLR implicit $lr, implicit $rm, implicit $r3

# End machine code for function c.

*** Bad machine code: PHI operand is not live-out from predecessor ***
- function:    c
- basic block: %bb.2 if.end (0x8168a95e0)
- instruction: %3:gprc = PHI %0:gprc, %bb.0, %2:gprc, %bb.1
- operand 1:   %0:gprc
fatal error: error in backend: Found 1 machine code errors.

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