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Author	SHA1	Message	Date
Ruslan Garipov	9225a0edf0	Merge branch 'fix/winedump_loop' into 'master' Avoid the for-loop be optimized out See merge request wine/wine!6780	2024-11-16 11:32:03 +00:00
Ruslan Garipov	a2c3cb4050	Avoid the for-loop be optimized out This stops GCC from optimizing out a for-loop inside the dump_cv_sst_src_module() function, when tools/winedump is compiled with optimization settings -O1 or higher. Because the baseSrcLn field of the 'struct OMFSourceFile' was declared as a flexible array of one element and it is an interior member of the structure: typedef struct OMFSourceFile { unsigned short cSeg; unsigned short reserved; unsigned int baseSrcLn[1]; unsigned short cFName; char Name; } OMFSourceFile; The compiler/optimizer assumes that the baseSrcLn array may have only zero or one element. And generates the corresponding code. The following shows code that GCC 14.2.1 generates before and after this patch. Before patch: # this printf(3)'s "File table: ..." 524f: call 4160 <printf@plt> # r15 stores sourceFile->cSeg; assigned above. 5254: cmpw $0x0,(%r12) # r12 is sourceFile 525a: je 527e <dump_codeview+0x70e> 525c: lea 0x4(%r12,%r15,4),%rax #rax is seg_info_dw 5261: mov 0x4(%r12),%r8d # sourceFile->baseSrcLn[0] 5266: mov $0x1,%esi 526b: lea 0x402fe(%rip),%rdi # 45570 5272: mov 0x4(%rax),%ecx 5275: mov (%rax),%edx 5277: xor %eax,%eax 5279: call 4160 <printf@plt> 527e: movzbl (%r14),%eax # eax = sourceModule + ofs The code checks if the sourceFile->cSeg is zero or not, and if not it printf(3)'s information about the first element in the baseSrcLn and first offset pair. There is no for-loop there, only its first iteration. After patch: # this printf(3)'s "File table: ..." 525c: call 4160 <printf@plt> # r12 is seg_info_dw and r15 stores integer 1; both assigned above. # r15 is `i' -- the loop counter. 5261: cmpw $0x0,(%r14) # r14 is sourceFile 5266: je 529f <dump_codeview+0x72f> 5268: nopl 0x0(%rax,%rax,1) 526f: 5270: mov -0x8(%r12,%r15,8),%edx 5275: mov -0x4(%r12,%r15,8),%ecx 527a: mov %r15d,%esi 527d: xor %eax,%eax 527f: mov (%r14,%r15,4),%r8d # sourceFile->baseSrcLn[i] 5283: lea 0x402e6(%rip),%rdi # 45570 528a: add $0x1,%r15 528e: call 4160 <printf@plt> 5293: movzwl (%r14),%eax 5297: lea -0x1(%r15),%edx 529b: cmp %eax,%edx 529d: jl 5270 <dump_codeview+0x700> 529f: mov 0x18(%rsp),%rax # rax = sourceModule + ofs The for-loop now is where it should be. Signed-off-by: Ruslan Garipov <ruslanngaripov@gmail.com>	2024-11-10 00:09:42 +05:00

Author

SHA1

Message

Date

Ruslan Garipov

9225a0edf0

Merge branch 'fix/winedump_loop' into 'master'

Avoid the for-loop be optimized out

See merge request wine/wine!6780

2024-11-16 11:32:03 +00:00

Ruslan Garipov

a2c3cb4050

Avoid the for-loop be optimized out

This stops GCC from optimizing out a for-loop inside the
dump_cv_sst_src_module() function, when tools/winedump is compiled with
optimization settings -O1 or higher.

Because the baseSrcLn field of the 'struct OMFSourceFile' was declared
as a flexible array of one element **and it is an interior member** of
the structure:

  typedef struct OMFSourceFile
  {
      unsigned short  cSeg;
      unsigned short  reserved;
      unsigned int    baseSrcLn[1];
      unsigned short  cFName;
      char            Name;
  } OMFSourceFile;

The compiler/optimizer assumes that the baseSrcLn array may have only
zero or one element.  And generates the corresponding code.

The following shows code that GCC 14.2.1 generates before and after this
patch.

Before patch:

  # this printf(3)'s "File table: ..."
  524f:  call   4160 <printf@plt>
  # r15 stores sourceFile->cSeg; assigned above.
  5254:   cmpw   $0x0,(%r12)  # r12 is sourceFile
  525a:   je     527e <dump_codeview+0x70e>
  525c:   lea    0x4(%r12,%r15,4),%rax  #rax is seg_info_dw
  5261:   mov    0x4(%r12),%r8d  # sourceFile->baseSrcLn[0]
  5266:   mov    $0x1,%esi
  526b:   lea    0x402fe(%rip),%rdi        # 45570
  5272:   mov    0x4(%rax),%ecx
  5275:   mov    (%rax),%edx
  5277:   xor    %eax,%eax
  5279:   call   4160 <printf@plt>
  527e:   movzbl (%r14),%eax  # eax = sourceModule + ofs

The code checks if the sourceFile->cSeg is zero or not, and if not it
printf(3)'s information about the first element in the baseSrcLn and
first offset pair.  There is no for-loop there, only its first
iteration.

After patch:

  # this printf(3)'s "File table: ..."
  525c:  call   4160 <printf@plt>
  # r12 is seg_info_dw and r15 stores integer 1; both assigned above.
  # r15 is `i' -- the loop counter.
  5261:  cmpw   $0x0,(%r14)  # r14 is sourceFile
  5266:  je     529f <dump_codeview+0x72f>
  5268:  nopl   0x0(%rax,%rax,1)
  526f:
  5270:  mov    -0x8(%r12,%r15,8),%edx
  5275:  mov    -0x4(%r12,%r15,8),%ecx
  527a:  mov    %r15d,%esi
  527d:  xor    %eax,%eax
  527f:  mov    (%r14,%r15,4),%r8d  # sourceFile->baseSrcLn[i]
  5283:  lea    0x402e6(%rip),%rdi        # 45570
  528a:  add    $0x1,%r15
  528e:  call   4160 <printf@plt>
  5293:  movzwl (%r14),%eax
  5297:  lea    -0x1(%r15),%edx
  529b:  cmp    %eax,%edx
  529d:  jl     5270 <dump_codeview+0x700>
  529f:  mov    0x18(%rsp),%rax  # rax = sourceModule + ofs

The for-loop now is where it should be.

Signed-off-by: Ruslan Garipov <ruslanngaripov@gmail.com>

2024-11-10 00:09:42 +05:00

1 changed files with 3 additions and 3 deletions

									
										6

include/wine/mscvpdb.h
									
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				@ -2779,9 +2779,9 @@ typedef struct OMFSourceFile

				{

				    unsigned short  cSeg;

				    unsigned short  reserved;

				    unsigned int    baseSrcLn[1];

				    unsigned short  cFName;

				    char            Name;

				    unsigned int    baseSrcLn[];

				    /* unsigned short  cFName; */

				    /* char            Name; */

				} OMFSourceFile;

				typedef struct OMFSourceModule

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