http://llvm.org/bugs/show_bug.cgi?id=12460
Bug #: 12460
Summary: load not folded if ShouldEmitAsBranches is true
Product: libraries
Version: trunk
Platform: PC
OS/Version: All
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
In
%struct.cmdline_options = type { i8*, i8*, i8, i8, i8, i8 }
@g_options = global %struct.cmdline_options zeroinitializer, align 8
@foobar = global i32* null, align 8
define void @_Z11processargsv() uwtable ssp {
%1 = load i8* getelementptr inbounds (%struct.cmdline_options* @g_options,
i64 0, i32 3), align 1, !range !0
%2 = icmp eq i8 %1, 0
%3 = load i8* getelementptr inbounds (%struct.cmdline_options* @g_options,
i64 0, i32 5), align 1, !range !0
%4 = icmp eq i8 %3, 0
%or.cond = or i1 %2, %4
br i1 %or.cond, label %6, label %5
; <label>:5 ; preds = %0
tail call void @_Z3foov()
br label %6
; <label>:6 ; preds = %0, %5
ret void
}
declare void @_Z3foov()
!0 = metadata !{i8 0, i8 2}
We decide to split the or into multiple branches and produce
cmpb $0, _g_options+17(%rip)
je LBB0_2
movb _g_options+19(%rip), %al
testb %al, %al
jne LBB0_3
The first load is folded into the compare, but the second one is not.
In this particular testcase the best is probably to not split, but the issues
is more general. llc -view-isel-dags shows both loads in the first BB, so we
are probably just splitting the 'or' too late.
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