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llvm-mirror/test/CodeGen/X86/subreg-to-reg-1.ll
Dan Gohman 74fa421281 Re-enable elimination of unnecessary SUBREG_TO_REG instructions in
LowerSubregs, and fix an x86-64 isel bug that this exposed.

SUBREG_TO_REG for x86-64 implicit zero extension is only safe for
isel to generate when the source is known to always have zeros in
the high 32 bits. The EXTRACT_SUBREG instruction does not clear
the high 32 bits.

llvm-svn: 54444
2008-08-07 02:54:50 +00:00

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LLVM

; RUN: llvm-as < %s | llc -march=x86-64 | grep {movl %e.\*, %e.\*} | count 1
; Don't eliminate or coalesce away the explicit zero-extension!
define i64 @foo(i64 %a) {
%b = add i64 %a, 4294967295
%c = and i64 %b, 4294967295
%d = add i64 %c, 1
ret i64 %d
}