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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123752 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2011-01-18 07:47:48 +00:00
parent 899407533a
commit 908d8e82b5
1 changed files with 20 additions and 0 deletions
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20
lib/Target/README.txt
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@ -2295,3 +2295,23 @@ avoids partial register stalls in some important cases.
//===---------------------------------------------------------------------===//
We miss an optzn when lowering divide by some constants. For example:
int test(int x) { return x/10; }
We produce:
_test: ## @test
## BB#0: ## %entry
movslq %edi, %rax
imulq $1717986919, %rax, %rax ## imm = 0x66666667
movq %rax, %rcx
shrq $63, %rcx
** shrq $32, %rax
** sarl $2, %eax
addl %ecx, %eax
ret
The two starred instructions could be replaced with a "sarl $34, %rax". This
occurs in 186.crafty very frequently.
//===---------------------------------------------------------------------===//