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<base href="https://bugs.llvm.org/">
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<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - DeadArgumentEliminationPass eliminates live return value"
href="https://bugs.llvm.org/show_bug.cgi?id=47444">47444</a>
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</tr>
<tr>
<th>Summary</th>
<td>DeadArgumentEliminationPass eliminates live return value
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>11.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Interprocedural Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>tomasz.miasko@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<pre>In example below, return values from functions f & g are live, but
DeadArgumentEliminationPass incorrectly removes the "return value 1 from g":
Args: opt -S -deadargelim -debug -print-before-all -print-after-all
*** IR Dump Before Dead Argument Elimination ***
; ModuleID = '<stdin>'
source_filename = "b.7rcbfp3g-cgu.0"
target datalayout =
"e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: nonlazybind
define internal { i64, i64 } @f(i64 %a, i64 %b) #0 {
start:
%0 = insertvalue { i64, i64 } undef, i64 %a, 0
%1 = insertvalue { i64, i64 } %0, i64 %b, 1
ret { i64, i64 } %1
}
; Function Attrs: nonlazybind
define internal { i64, i64 } @g(i64 %a, i64 %b) #0 {
start:
%0 = call { i64, i64 } @f(i64 %a, i64 %b)
ret { i64, i64 } %0
}
; Function Attrs: nonlazybind
declare dso_local i32 @test(i64, i64) #0
; Function Attrs: nonlazybind
define i32 @main(i32 %argc, i8** %argv) #0 {
start:
%x = call { i64, i64 } @g(i64 13, i64 42)
%x.0 = extractvalue { i64, i64 } %x, 0
%x.1 = extractvalue { i64, i64 } %x, 1
%z = bitcast i64 %x.0 to i64
%y = call { i64, i64 } @f(i64 %x.0, i64 %x.1)
%y.0 = extractvalue { i64, i64 } %y, 0
%y.1 = extractvalue { i64, i64 } %y, 1
%0 = call i32 @test(i64 %x.0, i64 %y.1)
ret i32 %0
}
attributes #0 = { nonlazybind "target-cpu"="x86-64" }
!llvm.module.flags = !{!0, !1, !2}
!0 = !{i32 7, !"PIC Level", i32 2}
!1 = !{i32 7, !"PIE Level", i32 2}
!2 = !{i32 2, !"RtLibUseGOT", i32 1}
DeadArgumentEliminationPass - Deleting dead varargs
DeadArgumentEliminationPass - Determining liveness
DeadArgumentEliminationPass - Inspecting callers for fn: f
DeadArgumentEliminationPass - Inspecting args for fn: f
DeadArgumentEliminationPass - Inspecting callers for fn: g
DeadArgumentEliminationPass - Marking Return value #0 of function g live
DeadArgumentEliminationPass - Marking Return value #0 of function f live
DeadArgumentEliminationPass - Marking Argument #0 of function f live
DeadArgumentEliminationPass - Marking Return value #1 of function f live
DeadArgumentEliminationPass - Marking Argument #1 of function f live
DeadArgumentEliminationPass - Inspecting args for fn: g
DeadArgumentEliminationPass - Marking Argument #0 of function g live
DeadArgumentEliminationPass - Marking Argument #1 of function g live
DeadArgumentEliminationPass - Intrinsically live fn: test
DeadArgumentEliminationPass - Intrinsically live fn: main
DeadArgumentEliminationPass - Removing return value 1 from g
*** IR Dump After Dead Argument Elimination ***
; ModuleID = '<stdin>'
source_filename = "b.7rcbfp3g-cgu.0"
target datalayout =
"e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: nonlazybind
define internal { i64, i64 } @f(i64 %a, i64 %b) #0 {
start:
%0 = insertvalue { i64, i64 } undef, i64 %a, 0
%1 = insertvalue { i64, i64 } %0, i64 %b, 1
ret { i64, i64 } %1
}
; Function Attrs: nonlazybind
define internal i64 @g(i64 %a, i64 %b) #0 {
start:
%0 = call { i64, i64 } @f(i64 %a, i64 %b)
%oldret = extractvalue { i64, i64 } %0, 0
ret i64 %oldret
}
; Function Attrs: nonlazybind
declare dso_local i32 @test(i64, i64) #0
; Function Attrs: nonlazybind
define i32 @main(i32 %argc, i8** %argv) #0 {
start:
%x = call i64 @g(i64 13, i64 42)
%oldret = insertvalue { i64, i64 } undef, i64 %x, 0
%x.0 = extractvalue { i64, i64 } %oldret, 0
%x.1 = extractvalue { i64, i64 } %oldret, 1
%z = bitcast i64 %x.0 to i64
%y = call { i64, i64 } @f(i64 %x.0, i64 %x.1)
%y.0 = extractvalue { i64, i64 } %y, 0
%y.1 = extractvalue { i64, i64 } %y, 1
%0 = call i32 @test(i64 %x.0, i64 %y.1)
ret i32 %0
}
attributes #0 = { nonlazybind "target-cpu"="x86-64" }
!llvm.module.flags = !{!0, !1, !2}
!0 = !{i32 7, !"PIC Level", i32 2}
!1 = !{i32 7, !"PIE Level", i32 2}
!2 = !{i32 2, !"RtLibUseGOT", i32 1}</pre>
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