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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - x86_64 backend sometimes generates 'leaq (%rsp), %x' rather than 'movq %rsp, %x'"
href="https://llvm.org/bugs/show_bug.cgi?id=29022">29022</a>
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<tr>
<th>Summary</th>
<td>x86_64 backend sometimes generates 'leaq (%rsp), %x' rather than 'movq %rsp, %x'
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</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>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>richard-llvm@metafoo.co.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mkuper@google.com
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>.cpp source:
#include <string>
int f() {
int a = std::string().size();
int b = std::string().size();
return a + b;
}
IR:
; ModuleID = '-'
source_filename = "-"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%"class.std::basic_string" = type { i8* }
; Function Attrs: nounwind uwtable
define i32 @_Z1fv() local_unnamed_addr {
entry:
%temp.lvalue = alloca %"class.std::basic_string", align 8
%temp.lvalue1 = alloca %"class.std::basic_string", align 8
call void @_ZNSsC2Ev(%"class.std::basic_string"* nonnull %temp.lvalue)
%call = call i64 @_ZNKSs4sizeEv(%"class.std::basic_string"* nonnull
%temp.lvalue)
%conv = trunc i64 %call to i32
call void @_ZNSsD2Ev(%"class.std::basic_string"* nonnull %temp.lvalue)
call void @_ZNSsC2Ev(%"class.std::basic_string"* nonnull %temp.lvalue1)
%call2 = call i64 @_ZNKSs4sizeEv(%"class.std::basic_string"* nonnull
%temp.lvalue1)
%conv3 = trunc i64 %call2 to i32
call void @_ZNSsD2Ev(%"class.std::basic_string"* nonnull %temp.lvalue1)
%add = add nsw i32 %conv3, %conv
ret i32 %add
}
; Function Attrs: nounwind uwtable
declare void @_ZNSsC2Ev(%"class.std::basic_string"* %this) unnamed_addr
; Function Attrs: norecurse nounwind uwtable
declare i64 @_ZNKSs4sizeEv(%"class.std::basic_string"* %this)
local_unnamed_addr
; Function Attrs: nounwind uwtable
declare void @_ZNSsD2Ev(%"class.std::basic_string"* %this) unnamed_addr
This generates the following instruction:
leaq (%rsp), %r15
That seems silly; we should use a movq instead.</pre>
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