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Catch a corner case where adding the padding to the "TType base offset" field

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will eliminate the need for padding in the "Call site table length". E.g., if
we have this:

    GCC_except_table1:
    Lexception1:
        .byte   0xff  ## @LPStart Encoding = omit
        .byte   0x9b  ## @TType Encoding = indirect pcrel sdata4
        .byte   0x7f  ## @TType base offset
        .byte   0x03  ## Call site Encoding = udata4
        .byte   0x89  ## Call site table length

with padding of 1. We want to emit the padding like this:
 
    GCC_except_table1:
    Lexception1:
        .byte   0xff  ## @LPStart Encoding = omit
        .byte   0x9b  ## @TType Encoding = indirect pcrel sdata4
        .byte   0xff  ## @TType base offset
        .space  1,0   ## Padding
        .byte   0x03  ## Call site Encoding = udata4
        .byte   0x89  ## Call site table length

and not with padding on the "Call site table length" entry.

llvm-svn: 97183
This commit is contained in:
Bill Wendling 2010-02-25 23:52:44 +00:00
parent f433645431
commit 788d3707a8
1 changed files with 44 additions and 2 deletions
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46
lib/CodeGen/AsmPrinter/DwarfException.cpp
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@ -745,10 +745,52 @@ void DwarfException::EmitExceptionTable() {
TTypeBaseOffset; // TType base offset
unsigned SizeAlign = (4 - TotalSize) & 3;
if (HaveTTData)
if (HaveTTData) {
// Account for any extra padded that will be added to the call site table
// length.
EmitULEB128(TTypeBaseOffset + SizeAlign, "@TType base offset");
unsigned Offset = TTypeBaseOffset + SizeAlign;
unsigned OffsetSize = MCAsmInfo::getULEB128Size(Offset);
unsigned TTypeBaseOverflow = 0;
// If adding the extra alignment to the TType base offset makes the new
// value of TTypeBaseOffset overflow (i.e., go from encoded as 1 byte to 2
// bytes), then the padding needs to be smaller by that amount.
if (OffsetSize != TTypeBaseOffsetSize) {
assert((int)OffsetSize - (int)TTypeBaseOffsetSize);
TTypeBaseOverflow = OffsetSize - TTypeBaseOffsetSize;
assert(TTypeBaseOffsetSize >= SizeAlign);
SizeAlign -= TTypeBaseOverflow;
}
if (!TTypeBaseOverflow || SizeAlign != 0)
EmitULEB128(Offset, "@TType base offset");
else
// If adding the extra padding to this offset causes it to buffer to the
// size of the padding needed, then we should perform the padding here and
// not at the call site table below. E.g. if we have this:
//
// GCC_except_table1:
// Lexception1:
// .byte 0xff ## @LPStart Encoding = omit
// .byte 0x9b ## @TType Encoding = indirect pcrel sdata4
// .byte 0x7f ## @TType base offset
// .byte 0x03 ## Call site Encoding = udata4
// .byte 0x89 ## Call site table length
//
// with padding of 1. We want to emit the padding like this:
//
// GCC_except_table1:
// Lexception1:
// .byte 0xff ## @LPStart Encoding = omit
// .byte 0x9b ## @TType Encoding = indirect pcrel sdata4
// .byte 0xff ## @TType base offset
// .space 1,0 ## Padding
// .byte 0x03 ## Call site Encoding = udata4
// .byte 0x89 ## Call site table length
//
// and not with padding on the "Call site table length" entry.
EmitULEB128(TTypeBaseOffset, "@TType base offset", TTypeBaseOverflow);
}
// SjLj Exception handling
if (IsSJLJ) {