[mips][micromips] Fix values in .gcc_except_table for -fPIC

[abeserminji]

Summary

When a landing pad is calculated in a program that is compiled
for micromips with -fPIC flag, it will point to an even address.
Such an error will cause a segmentation fault, as the instructions
in micromips are aligned on odd addresses. This patch sets the
last bit of the offset where a landing pad is, to 1, which will
effectively be an odd address and point to the instruction exactly.

Patch D52985 fixed this issue for -static compilation.

[atanasyan]

LGTM

[MaskRay]

llvm/trunk/test/CodeGen/Mips/micromips-b-range.ll

16 ↗

(On Diff #185875)

Changes to this file seem wrong. I have produced an assembly file and assembled it with mipsel-linux-gnu-gcc -mmicromips. The values are even.

Apologies, but I am going to revert the MCExpr.cpp change in D157655.

[wzssyqa]

Yes. microMIPS support needs lots of work.

lib/MC/MCExpr.cpp

static void AttemptToFoldSymbolOffsetDifference(
   if (Addrs && (&SecA != &SecB))
     Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
 
   // Pointers to Thumb symbols need to have their low-bit set to allow
   // for interworking.
   if (Asm->isThumbFunc(&SA))
     Addend |= 1;
 
+  // If symbol is labeled as micromips, we set low-bit to ensure
+  // correct offset in .gcc_except_table
+  if (Asm->getBackend().isMicroMips(&SA))
+    Addend |= 1;
+
   // Clear the symbol expr pointers to indicate we have folded these
   // operands.
   A = B = nullptr;
 }
 
 /// Evaluate the result of an add between (conceptually) two MCValues.
 ///
 /// This routine conceptually attempts to construct an MCValue:

test/CodeGen/Mips/micromips-b-range.ll

 ; RUN: llc -march=mips -relocation-model=pic -mattr=+micromips \
 ; RUN:     -filetype=obj -o - %s | llvm-objdump -d - | FileCheck %s
 
 ; CHECK-LABEL: foo:
 ; CHECK-NEXT:     0:  41 a2 00 00   lui $2, 0
 ; CHECK-NEXT:     4:  30 42 00 00   addiu $2, $2, 0
 ; CHECK-NEXT:     8:  03 22 11 50   addu  $2, $2, $25
 ; CHECK-NEXT:     c:  fc 42 00 00   lw  $2, 0($2)
 ; CHECK-NEXT:    10:  69 20         lw16  $2, 0($2)
 ; CHECK-NEXT:    12:  40 c2 00 14   bgtz  $2, 44 <foo+0x3e>
 ; CHECK-NEXT:    16:  00 00 00 00   nop
 ; CHECK-NEXT:    1a:  33 bd ff f8   addiu $sp, $sp, -8
 ; CHECK-NEXT:    1e:  fb fd 00 00   sw  $ra, 0($sp)
 ; CHECK-NEXT:    22:  41 a1 00 01   lui $1, 1
 ; CHECK-NEXT:    26:  40 60 00 02   bal 8 <foo+0x2e>
-; CHECK-NEXT:    2a:  30 21 04 68   addiu $1, $1, 1128
+; CHECK-NEXT:    2a:  30 21 04 69   addiu $1, $1, 1129
 ; CHECK-NEXT:    2e:  00 3f 09 50   addu  $1, $ra, $1
 ; CHECK-NEXT:    32:  ff fd 00 00   lw  $ra, 0($sp)
 ; CHECK-NEXT:    36:  00 01 0f 3c   jr  $1
 ; CHECK-NEXT:    3a:  33 bd 00 08   addiu $sp, $sp, 8
 ; CHECK-NEXT:    3e:  94 00 00 02   b 8 <foo+0x46>
 ; CHECK-NEXT:    42:  00 00 00 00   nop
 ; CHECK-NEXT:    46:  30 20 4e 1f   addiu $1, $zero, 19999
 ; CHECK-NEXT:    4a:  b4 22 00 14   bne $2, $1, 44 <foo+0x76>
 ; CHECK-NEXT:    4e:  00 00 00 00   nop
 ; CHECK-NEXT:    52:  33 bd ff f8   addiu $sp, $sp, -8
 ; CHECK-NEXT:    56:  fb fd 00 00   sw  $ra, 0($sp)
 ; CHECK-NEXT:    5a:  41 a1 00 01   lui $1, 1
 ; CHECK-NEXT:    5e:  40 60 00 02   bal 8 <foo+0x66>
-; CHECK-NEXT:    62:  30 21 04 5c   addiu $1, $1, 1116
+; CHECK-NEXT:    62:  30 21 04 5d   addiu $1, $1, 1117
 ; CHECK-NEXT:    66:  00 3f 09 50   addu  $1, $ra, $1
 ; CHECK-NEXT:    6a:  ff fd 00 00   lw  $ra, 0($sp)
 ; CHECK-NEXT:    6e:  00 01 0f 3c   jr  $1
 ; CHECK-NEXT:    72:  33 bd 00 08   addiu $sp, $sp, 8
 ; CHECK-NEXT:    76:  30 20 27 0f   addiu $1, $zero, 9999
 ; CHECK-NEXT:    7a:  94 22 00 14   beq $2, $1, 44 <foo+0xa6>
 ; CHECK-NEXT:    7e:  00 00 00 00   nop
 ; CHECK-NEXT:    82:  33 bd ff f8   addiu $sp, $sp, -8
 ; CHECK-NEXT:    86:  fb fd 00 00   sw  $ra, 0($sp)
 ; CHECK-NEXT:    8a:  41 a1 00 01   lui $1, 1
 ; CHECK-NEXT:    8e:  40 60 00 02   bal 8 <foo+0x96>
-; CHECK-NEXT:    92:  30 21 04 2c   addiu $1, $1, 1068
+; CHECK-NEXT:    92:  30 21 04 2d   addiu $1, $1, 1069
 ; CHECK-NEXT:    96:  00 3f 09 50   addu  $1, $ra, $1
 ; CHECK-NEXT:    9a:  ff fd 00 00   lw  $ra, 0($sp)
 ; CHECK-NEXT:    9e:  00 01 0f 3c   jr  $1
 ; CHECK-NEXT:    a2:  33 bd 00 08   addiu $sp, $sp, 8
 ; CHECK:                ...
 ; CHECK-NEXT: 1046a:  94 00 00 02   b 8 <foo+0x10472>
 ; CHECK-NEXT: 1046e:  00 00 00 00   nop
 ; CHECK-NEXT: 10472:  33 bd ff f8   addiu $sp, $sp, -8
 ; CHECK-NEXT: 10476:  fb fd 00 00   sw  $ra, 0($sp)
 ; CHECK-NEXT: 1047a:  41 a1 00 01   lui $1, 1
 ; CHECK-NEXT: 1047e:  40 60 00 02   bal 8 <foo+0x10486>
-; CHECK-NEXT: 10482:  30 21 04 00   addiu $1, $1, 1024
+; CHECK-NEXT: 10482:  30 21 04 01   addiu $1, $1, 1025
 ; CHECK-NEXT: 10486:  00 3f 09 50   addu  $1, $ra, $1
 ; CHECK-NEXT: 1048a:  ff fd 00 00   lw  $ra, 0($sp)
 ; CHECK-NEXT: 1048e:  00 01 0f 3c   jr  $1
 ; CHECK-NEXT: 10492:  33 bd 00 08   addiu $sp, $sp, 8
 ; CHECK-NEXT: 10496:  94 00 00 02   b 8 <foo+0x1049e>
 
 @x = external global i32, align 4
 

test/DebugInfo/Mips/eh_frame.ll

-; RUN: llc -mtriple mips-unknown-linux-gnu -mattr=+micromips -O3 -filetype=obj -o - %s | llvm-readelf -r | FileCheck %s
-
-; CHECK: .rel.eh_frame
-; CHECK: DW.ref.__gxx_personality_v0
-; CHECK-NEXT: .text
-; CHECK-NEXT: .gcc_except_table
+; RUN: llc -mtriple mips-unknown-linux-gnu -mattr=+micromips -relocation-model=static -O3 -filetype=obj -o - %s | \
+; RUN:     llvm-readelf -r | FileCheck %s --check-prefix=CHECK-READELF
+; RUN: llc -mtriple mips-unknown-linux-gnu -mattr=+micromips -relocation-model=pic -O3 -filetype=obj -o - %s | \
+; RUN:     llvm-readelf -r | FileCheck %s --check-prefix=CHECK-READELF
+; RUN: llc -mtriple mips-unknown-linux-gnu -mattr=+micromips -relocation-model=static -O3 -filetype=obj -o - %s | \
+; RUN:     llvm-objdump -s -j .gcc_except_table - | FileCheck %s --check-prefix=CHECK-EXCEPT-TABLE-STATIC
+; RUN: llc -mtriple mips-unknown-linux-gnu -mattr=+micromips -relocation-model=pic -O3 -filetype=obj -o - %s | \
+; RUN:     llvm-objdump -s -j .gcc_except_table - | FileCheck %s --check-prefix=CHECK-EXCEPT-TABLE-PIC
+
+; CHECK-READELF: .rel.eh_frame
+; CHECK-READELF: DW.ref.__gxx_personality_v0
+; CHECK-READELF-NEXT: .text
+; CHECK-READELF-NEXT: .gcc_except_table
+
+; CHECK-EXCEPT-TABLE-STATIC: 0000 ff9b1501 0c011500 00150e23 01231e00  ...........#.#..
+; CHECK-EXCEPT-TABLE-STATIC: 0010 00010000 00000000
+; CHECK-EXCEPT-TABLE-PIC:    0000 ff9b1501 0c012d00 002d133f 013f2a00 ......-..-.?.?*.
+; CHECK-EXCEPT-TABLE-PIC:    0010 00010000 00000000                    ........
 
 @_ZTIi = external constant i8*
 
 define dso_local i32 @main() local_unnamed_addr personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
 entry:
   %exception.i = tail call i8* @__cxa_allocate_exception(i32 4) nounwind
   %0 = bitcast i8* %exception.i to i32*
   store i32 5, i32* %0, align 16