https://llvm.org/bugs/show_bug.cgi?id=27661
Bug ID: 27661
Summary: llvm generates many push and pop
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: hjl.to...@gmail.com
CC: david.l.kreit...@intel.com, llvm-bugs@lists.llvm.org,
zia.ans...@intel.com
Classification: Unclassified
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
--
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