2009-09-08 23:54:48 +00:00
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; RUN: llc < %s -march=x86-64 | grep lea | count 3
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; RUN: llc < %s -march=x86-64 | grep shl | count 1
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; RUN: llc < %s -march=x86-64 | not grep imul
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Optimize some 64-bit multiplication by constants into two lea's or one lea + shl since imulq is slow (latency 5). e.g.
x * 40
=>
shlq $3, %rdi
leaq (%rdi,%rdi,4), %rax
This has the added benefit of allowing more multiply to be folded into addressing mode. e.g.
a * 24 + b
=>
leaq (%rdi,%rdi,2), %rax
leaq (%rsi,%rax,8), %rax
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67917 91177308-0d34-0410-b5e6-96231b3b80d8
2009-03-28 05:57:29 +00:00
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define i64 @t1(i64 %a) nounwind readnone {
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entry:
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%0 = mul i64 %a, 81 ; <i64> [#uses=1]
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ret i64 %0
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}
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define i64 @t2(i64 %a) nounwind readnone {
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entry:
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%0 = mul i64 %a, 40 ; <i64> [#uses=1]
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ret i64 %0
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}
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