https://bugs.llvm.org/show_bug.cgi?id=34471
Bug ID: 34471
Summary: small improvement to switch compilation
Product: clang
Version: unspecified
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: d...@yost.com
CC: llvm-bugs@lists.llvm.org
This code
int switcher(int x) {
switch(x) {
case 17: return 17;
case 42: return 42;
default: break;
}
return 0;
}
generates this:
switch i32 %4, label %7 [
i32 17, label %5
i32 42, label %6
]
; <label>:5: ; preds = %1
store i32 17, i32* %2, align 4
br label %9
; <label>:6: ; preds = %1
store i32 42, i32* %2, align 4
br label %9
I suspect that most targets would generate better code from equivalent llvm
output in which both cases jump to a common label that returns x instead of
jumping to separate labels that eventually return the constants 17 and 42.
Certainly the Mill compiler would generate better code. :)
See https://www.youtube.com/watch?time_continue=2191&v=FeYsKF3a14k
--
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
