<html>
<head>
<base href="https://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - llvm generates many push and pop"
href="https://llvm.org/bugs/show_bug.cgi?id=27661">27661</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>llvm generates many push and pop
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</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>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>hjl.tools@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>david.l.kreitzer@intel.com, llvm-bugs@lists.llvm.org, zia.ansari@intel.com
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>At -O2 for x86-64, llvm generates an extra subq and many push/pop
---
extern void foo1 (void *, void *, void *, void *, void *, void *, int, int,
void *);
extern void foo2 (void *, void *, void *, void *, void *, void *, int, void *);
void
bar (int x)
{
int i1, i2, i3, i4, i5, i6;
int i;
foo1 (&i1, &i2, &i3, &i4, &i5, &i6, 7, 8, &i);
foo2 (&i1, &i2, &i3, &i4, &i5, &i6, 8, &i);
}
---
bar: # @bar
.cfi_startproc
# BB#0:
pushq %rbp
.Ltmp0:
.cfi_def_cfa_offset 16
pushq %r15
.Ltmp1:
.cfi_def_cfa_offset 24
pushq %r14
.Ltmp2:
.cfi_def_cfa_offset 32
pushq %r13
.Ltmp3:
.cfi_def_cfa_offset 40
pushq %r12
.Ltmp4:
.cfi_def_cfa_offset 48
pushq %rbx
.Ltmp5:
.cfi_def_cfa_offset 56
subq $40, %rsp
.Ltmp6:
.cfi_def_cfa_offset 96
.Ltmp7:
.cfi_offset %rbx, -56
.Ltmp8:
.cfi_offset %r12, -48
.Ltmp9:
.cfi_offset %r13, -40
.Ltmp10:
.cfi_offset %r14, -32
.Ltmp11:
.cfi_offset %r15, -24
.Ltmp12:
.cfi_offset %rbp, -16
subq $8, %rsp <<<<<<<<<<<<<<< Extra subq.
.Ltmp13:
.cfi_adjust_cfa_offset 8
leaq 20(%rsp), %rax
leaq 44(%rsp), %rbx
leaq 40(%rsp), %r14
leaq 36(%rsp), %r15
leaq 32(%rsp), %r12
leaq 28(%rsp), %r13
leaq 24(%rsp), %rbp
movq %rbx, %rdi
movq %r14, %rsi
movq %r15, %rdx
movq %r12, %rcx
movq %r13, %r8
movq %rbp, %r9
pushq %rax
.Ltmp14:
.cfi_adjust_cfa_offset 8
pushq $8
.Ltmp15:
.cfi_adjust_cfa_offset 8
pushq $7
.Ltmp16:
.cfi_adjust_cfa_offset 8
callq foo1
addq $32, %rsp
.Ltmp17:
.cfi_adjust_cfa_offset -32
movq %rbx, %rdi
movq %r14, %rsi
movq %r15, %rdx
movq %r12, %rcx
movq %r13, %r8
movq %rbp, %r9
leaq 12(%rsp), %rax
pushq %rax
.Ltmp18:
.cfi_adjust_cfa_offset 8
pushq $8
.Ltmp19:
.cfi_adjust_cfa_offset 8
callq foo2
addq $56, %rsp
.Ltmp20:
.cfi_adjust_cfa_offset -16
popq %rbx
popq %r12
popq %r13
popq %r14
popq %r15
popq %rbp
retq
GCC 5.3.1 generates
bar:
.LFB0:
.cfi_startproc
pushq %rbx
.cfi_def_cfa_offset 16
.cfi_offset 3, -16
subq $40, %rsp
.cfi_def_cfa_offset 56
leaq 36(%rsp), %rbx
pushq %rbx
.cfi_def_cfa_offset 64
pushq $8
.cfi_def_cfa_offset 72
pushq $7
.cfi_def_cfa_offset 80
leaq 56(%rsp), %r9
leaq 52(%rsp), %r8
leaq 48(%rsp), %rcx
leaq 44(%rsp), %rdx
leaq 40(%rsp), %rsi
leaq 36(%rsp), %rdi
call foo1
addq $32, %rsp
.cfi_def_cfa_offset 48
pushq %rbx
.cfi_def_cfa_offset 56
pushq $8
.cfi_def_cfa_offset 64
leaq 40(%rsp), %r9
leaq 36(%rsp), %r8
leaq 32(%rsp), %rcx
leaq 28(%rsp), %rdx
leaq 24(%rsp), %rsi
leaq 20(%rsp), %rdi
call foo2
addq $48, %rsp
.cfi_def_cfa_offset 16
popq %rbx
.cfi_def_cfa_offset 8
ret</pre>
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