http://llvm.org/bugs/show_bug.cgi?id=4548
Summary: missed optimization: zext 8/16->32+udiv 32+trunc 32-
>8/16 -> udiv 8/16
Product: new-bugs
Version: unspecified
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: new bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
For the C code below:
uint8_t udiv_i8(uint8_t a, uint8_t b)
{
return a / b;
}
Clang generates this IR (at -O1/O2):
%conv = zext i8 %a to i32
%conv2 = zext i8 %b to i32
%div = udiv i32 %conv, %conv2
%conv3 = trunc i32 %div to i8
ret i8 %conv3
This should be optimized to this IR, since that is what the original C code
meant:
%div = udiv i8 %a, %b
ret i8 %div
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