https://llvm.org/bugs/show_bug.cgi?id=24590
Bug ID: 24590
Summary: clang-cl generates wrong addressing mode for table
lookup.
Product: tools
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: llvmc
Assignee: unassignedb...@nondot.org
Reporter: fbarch...@google.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 14781
--> https://llvm.org/bugs/attachment.cgi?id=14781&action=edit
source for test to reproduce table index bug
This code generates the wrong code for clang-cl. The indexing is lost.
const int fixed_invtbl8[256] = { 0, };
void f() {
char file[] = "";
__asm movd xmm0, dword ptr [fixed_invtbl8 + eax * 4]
}
Visual C:
cl /c test.c
dumpbin -disasm test.obj
0000000C: 66 0F 6E 04 85 00 movd xmm0,dword ptr _fixed_invtbl8[eax*4]
00 00 00
objdump -d test.obj
c: 66 0f 6e 04 85 00 00 movd 0x0(,%eax,4),%xmm0
13: 00 00
clang-cl /c test.c
dumpbin -disasm test.obj
00000034: 66 0F 6E 05 00 00 movd xmm0,dword ptr [_fixed_invtbl8]
00 00
34: 66 0f 6e 05 00 00 00 movd 0x0,%xmm0
3b: 00
The code will build and run, but produces the wrong result - it uses the first
int from the table.
A work around is to put the table into a register:
const int fixed_invtbl8[256] = { 0, };
void f() {
char file[] = "";
__asm lea ebx, fixed_invtbl8
__asm movd xmm0, dword ptr [ebx + eax * 4]
}
35: 8D 1D 00 00 00 00 lea ebx,[_fixed_invtbl8]
3B: 66 0F 6E 04 83 movd xmm0,dword ptr [ebx+eax*4]
Using clang-cl provided by chromium
third_party\llvm-build\Release+Asserts\bin\clang-cl.exe
--
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
