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author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-01-02 19:44:58 +0000 |
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committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-01-02 19:44:58 +0000 |
commit | 8c06aa1c597bb5c2c264a190bc35836f0a7b4cd5 (patch) | |
tree | ef29be4c79e78710d9b1b838d786df1cbf723a46 /test/CodeGen/X86/memset-2.ll | |
parent | 3458534f11417e0269401346e98331a9282c8573 (diff) | |
download | llvm-8c06aa1c597bb5c2c264a190bc35836f0a7b4cd5.tar.gz llvm-8c06aa1c597bb5c2c264a190bc35836f0a7b4cd5.tar.bz2 llvm-8c06aa1c597bb5c2c264a190bc35836f0a7b4cd5.tar.xz |
Lower the i8 extension in memset to a multiply instead of a potentially long series of shifts and ors.
We could implement a DAGCombine to turn x * 0x0101 back into logic operations
on targets that doesn't support the multiply or it is slow (p4) if someone cares
enough.
Example code:
void test(char *s, int a) {
__builtin_memset(s, a, 4);
}
before:
_test: ## @test
movzbl 8(%esp), %eax
movl %eax, %ecx
shll $8, %ecx
orl %eax, %ecx
movl %ecx, %eax
shll $16, %eax
orl %ecx, %eax
movl 4(%esp), %ecx
movl %eax, 4(%ecx)
movl %eax, (%ecx)
ret
after:
_test: ## @test
movzbl 8(%esp), %eax
imull $16843009, %eax, %eax ## imm = 0x1010101
movl 4(%esp), %ecx
movl %eax, 4(%ecx)
movl %eax, (%ecx)
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122707 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/CodeGen/X86/memset-2.ll')
-rw-r--r-- | test/CodeGen/X86/memset-2.ll | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/test/CodeGen/X86/memset-2.ll b/test/CodeGen/X86/memset-2.ll index 692965f6f7..11f619cd6d 100644 --- a/test/CodeGen/X86/memset-2.ll +++ b/test/CodeGen/X86/memset-2.ll @@ -17,3 +17,14 @@ entry: call void @llvm.memset.i32( i8* undef, i8 %c, i32 76, i32 1 ) nounwind unreachable } + +declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) nounwind + +define void @t3(i8* nocapture %s, i8 %a) nounwind { +entry: + tail call void @llvm.memset.p0i8.i32(i8* %s, i8 %a, i32 8, i32 1, i1 false) + ret void +; CHECK: t3: +; CHECK: imull $16843009 +} + |