http://llvm.org/bugs/show_bug.cgi?id=12113
Bug #: 12113
Summary: Dead store when handling larger-than-register shfits
Product: libraries
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
Consider:
unsigned int f(unsigned int x)
{
return 1ULL << ((x % 32));
}
When compiling with -m32, this turns into
f:
movl 4(%esp), %ecx
movl $1, %edx
shll %cl, %edx
xorb %al, %al
testb %al, %al
movl $0, %eax
cmovel %edx, %eax
ret
The xorb / testb / cmovel sequence is invariant wrt to the input.
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