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7feae20986
This tends to happen a lot with bitfield code generated by clang. A simple example for x86_64 is
uint64_t foo(uint64_t x) { return (x&1) << 42; }
which used to compile into bloated code:
shlq $42, %rdi ## encoding: [0x48,0xc1,0xe7,0x2a]
movabsq $4398046511104, %rax ## encoding: [0x48,0xb8,0x00,0x00,0x00,0x00,0x00,0x04,0x00,0x00]
andq %rdi, %rax ## encoding: [0x48,0x21,0xf8]
ret ## encoding: [0xc3]
with this patch we can fold the immediate into the and:
andq $1, %rdi ## encoding: [0x48,0x83,0xe7,0x01]
movq %rdi, %rax ## encoding: [0x48,0x89,0xf8]
shlq $42, %rax ## encoding: [0x48,0xc1,0xe0,0x2a]
ret ## encoding: [0xc3]
It's possible to save another byte by using 'andl' instead of 'andq' but I currently see no way of doing
that without making this code even more complicated. See the TODOs in the code.
llvm-svn: 129990
102 lines
1.9 KiB
LLVM
102 lines
1.9 KiB
LLVM
; RUN: llc < %s -march=x86-64 | FileCheck %s
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; PR5039
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define i32 @test1(i32 %x) nounwind {
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%and = shl i32 %x, 10
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%shl = and i32 %and, 31744
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ret i32 %shl
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; CHECK: test1:
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; CHECK: andl $31
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; CHECK: shll $10
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}
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define i32 @test2(i32 %x) nounwind {
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%or = shl i32 %x, 10
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%shl = or i32 %or, 31744
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ret i32 %shl
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; CHECK: test2:
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; CHECK: orl $31
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; CHECK: shll $10
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}
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define i32 @test3(i32 %x) nounwind {
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%xor = shl i32 %x, 10
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%shl = xor i32 %xor, 31744
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ret i32 %shl
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; CHECK: test3:
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; CHECK: xorl $31
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; CHECK: shll $10
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}
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define i64 @test4(i64 %x) nounwind {
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%and = shl i64 %x, 40
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%shl = and i64 %and, 264982302294016
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ret i64 %shl
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; CHECK: test4:
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; CHECK: andq $241
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; CHECK: shlq $40
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}
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define i64 @test5(i64 %x) nounwind {
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%and = shl i64 %x, 40
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%shl = and i64 %and, 34084860461056
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ret i64 %shl
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; CHECK: test5:
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; CHECK: andq $31
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; CHECK: shlq $40
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}
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define i64 @test6(i64 %x) nounwind {
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%and = shl i64 %x, 32
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%shl = and i64 %and, -281474976710656
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ret i64 %shl
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; CHECK: test6:
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; CHECK: andq $-65536
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; CHECK: shlq $32
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}
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define i64 @test7(i64 %x) nounwind {
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%or = shl i64 %x, 40
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%shl = or i64 %or, 264982302294016
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ret i64 %shl
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; CHECK: test7:
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; CHECK: orq $241
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; CHECK: shlq $40
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}
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define i64 @test8(i64 %x) nounwind {
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%or = shl i64 %x, 40
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%shl = or i64 %or, 34084860461056
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ret i64 %shl
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; CHECK: test8:
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; CHECK: orq $31
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; CHECK: shlq $40
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}
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define i64 @test9(i64 %x) nounwind {
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%xor = shl i64 %x, 40
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%shl = xor i64 %xor, 264982302294016
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ret i64 %shl
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; CHECK: test9:
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; CHECK: orq $241
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; CHECK: shlq $40
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}
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define i64 @test10(i64 %x) nounwind {
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%xor = shl i64 %x, 40
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%shl = xor i64 %xor, 34084860461056
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ret i64 %shl
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; CHECK: test10:
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; CHECK: xorq $31
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; CHECK: shlq $40
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}
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define i64 @test11(i64 %x) nounwind {
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%xor = shl i64 %x, 33
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%shl = xor i64 %xor, -562949953421312
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ret i64 %shl
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; CHECK: test11:
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; CHECK: xorq $-65536
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; CHECK: shlq $33
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}
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